Add a WEBP_NODISCARD

Change-Id: Ice66f2aa6358474d728fb19c571edc86ed139a49

CMakeLists.txt

@@ -51,6 +51,8 @@ option(WEBP_ENABLE_SWAP_16BIT_CSP "Enable byte swap for 16 bit colorspaces."
        OFF)
 set(WEBP_BITTRACE "0" CACHE STRING "Bit trace mode (0=none, 1=bit, 2=bytes)")
 set_property(CACHE WEBP_BITTRACE PROPERTY STRINGS 0 1 2)
+option(WEBP_ENABLE_WUNUSED_RESULT "Add [[nodiscard]] to some functions. \
+       CMake must be at least 3.21 to force C23" OFF)
 
 if(WEBP_LINK_STATIC)
   if(WIN32)
@@ -163,6 +165,17 @@ endif()
 
 set(CMAKE_C_VISIBILITY_PRESET hidden)
 
+if(WEBP_ENABLE_WUNUSED_RESULT)
+  if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.21.0)
+    set(CMAKE_C_STANDARD 23)
+  else()
+    unset(CMAKE_C_STANDARD)
+    add_compile_options($<$<COMPILE_LANGUAGE:C>:-std=gnu2x>)
+  endif()
+  add_compile_options(-Wunused-result)
+  add_definitions(-DWEBP_ENABLE_NODISCARD=1)
+endif()
+
 # ##############################################################################
 # Android only.
 if(ANDROID)

examples/anim_dump.c

@@ -98,7 +98,11 @@ int main(int argc, const char* argv[]) {
       for (i = 0; !error && i < image.num_frames; ++i) {
         W_CHAR out_file[1024];
         WebPDecBuffer buffer;
-        WebPInitDecBuffer(&buffer);
+        if (!WebPInitDecBuffer(&buffer)) {
+          fprintf(stderr, "Cannot init dec buffer\n");
+          error = 1;
+          continue;
+        }
         buffer.colorspace = MODE_RGBA;
         buffer.is_external_memory = 1;
         buffer.width = image.canvas_width;

examples/vwebp.c

@@ -613,7 +613,7 @@ int main(int argc, char* argv[]) {
 
   // Position iterator to last frame. Next call to HandleDisplay will wrap over.
   // We take this into account by bumping up loop_count.
-  WebPDemuxGetFrame(kParams.dmux, 0, curr);
+  if (!WebPDemuxGetFrame(kParams.dmux, 0, curr)) goto Error;
   if (kParams.loop_count) ++kParams.loop_count;
 
 #if defined(__unix__) || defined(__CYGWIN__)

src/dec/alpha_dec.c

@@ -13,18 +13,20 @@
 
 #include <stdlib.h>
 #include "src/dec/alphai_dec.h"
+#include "src/dec/vp8_dec.h"
 #include "src/dec/vp8i_dec.h"
 #include "src/dec/vp8li_dec.h"
 #include "src/dsp/dsp.h"
 #include "src/utils/quant_levels_dec_utils.h"
 #include "src/utils/utils.h"
 #include "src/webp/format_constants.h"
+#include "src/webp/types.h"
 
 //------------------------------------------------------------------------------
 // ALPHDecoder object.
 
 // Allocates a new alpha decoder instance.
-static ALPHDecoder* ALPHNew(void) {
+WEBP_NODISCARD static ALPHDecoder* ALPHNew(void) {
   ALPHDecoder* const dec = (ALPHDecoder*)WebPSafeCalloc(1ULL, sizeof(*dec));
   return dec;
 }
@@ -45,9 +47,9 @@ static void ALPHDelete(ALPHDecoder* const dec) {
 // header for alpha data stored using lossless compression.
 // Returns false in case of error in alpha header (data too short, invalid
 // compression method or filter, error in lossless header data etc).
-static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data,
+WEBP_NODISCARD static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data,
-                    size_t data_size, const VP8Io* const src_io,
+                                   size_t data_size, const VP8Io* const src_io,
-                    uint8_t* output) {
+                                   uint8_t* output) {
   int ok = 0;
   const uint8_t* const alpha_data = data + ALPHA_HEADER_LEN;
   const size_t alpha_data_size = data_size - ALPHA_HEADER_LEN;
@@ -79,7 +81,9 @@ static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data,
   }
 
   // Copy the necessary parameters from src_io to io
-  VP8InitIo(io);
+  if (!VP8InitIo(io)) {
+    return 0;
+  }
   WebPInitCustomIo(NULL, io);
   io->opaque = dec;
   io->width = src_io->width;
@@ -107,7 +111,8 @@ static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data,
 // starting from row number 'row'. It assumes that rows up to (row - 1) have
 // already been decoded.
 // Returns false in case of bitstream error.
-static int ALPHDecode(VP8Decoder* const dec, int row, int num_rows) {
+WEBP_NODISCARD static int ALPHDecode(VP8Decoder* const dec, int row,
+                                     int num_rows) {
   ALPHDecoder* const alph_dec = dec->alph_dec_;
   const int width = alph_dec->width_;
   const int height = alph_dec->io_.crop_bottom;
@@ -138,7 +143,8 @@ static int ALPHDecode(VP8Decoder* const dec, int row, int num_rows) {
   return 1;
 }
 
-static int AllocateAlphaPlane(VP8Decoder* const dec, const VP8Io* const io) {
+WEBP_NODISCARD static int AllocateAlphaPlane(VP8Decoder* const dec,
+                                             const VP8Io* const io) {
   const int stride = io->width;
   const int height = io->crop_bottom;
   const uint64_t alpha_size = (uint64_t)stride * height;
@@ -166,9 +172,9 @@ void WebPDeallocateAlphaMemory(VP8Decoder* const dec) {
 //------------------------------------------------------------------------------
 // Main entry point.
 
-const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec,
+WEBP_NODISCARD const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec,
-                                      const VP8Io* const io,
+                                                     const VP8Io* const io,
-                                      int row, int num_rows) {
+                                                     int row, int num_rows) {
   const int width = io->width;
   const int height = io->crop_bottom;
 

src/dec/idec_dec.c

@@ -17,8 +17,10 @@
 
 #include "src/dec/alphai_dec.h"
 #include "src/dec/webpi_dec.h"
+#include "src/dec/vp8_dec.h"
 #include "src/dec/vp8i_dec.h"
 #include "src/utils/utils.h"
+#include "src/webp/decode.h"
 
 // In append mode, buffer allocations increase as multiples of this value.
 // Needs to be a power of 2.
@@ -161,8 +163,9 @@ static void DoRemap(WebPIDecoder* const idec, ptrdiff_t offset) {
 
 // Appends data to the end of MemBuffer->buf_. It expands the allocated memory
 // size if required and also updates VP8BitReader's if new memory is allocated.
-static int AppendToMemBuffer(WebPIDecoder* const idec,
+WEBP_NODISCARD static int AppendToMemBuffer(WebPIDecoder* const idec,
-                             const uint8_t* const data, size_t data_size) {
+                                            const uint8_t* const data,
+                                            size_t data_size) {
   VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
   MemBuffer* const mem = &idec->mem_;
   const int need_compressed_alpha = NeedCompressedAlpha(idec);
@@ -203,8 +206,9 @@ static int AppendToMemBuffer(WebPIDecoder* const idec,
   return 1;
 }
 
-static int RemapMemBuffer(WebPIDecoder* const idec,
+WEBP_NODISCARD static int RemapMemBuffer(WebPIDecoder* const idec,
-                          const uint8_t* const data, size_t data_size) {
+                                         const uint8_t* const data,
+                                         size_t data_size) {
   MemBuffer* const mem = &idec->mem_;
   const uint8_t* const old_buf = mem->buf_;
   const uint8_t* const old_start =
@@ -237,7 +241,8 @@ static void ClearMemBuffer(MemBuffer* const mem) {
   }
 }
 
-static int CheckMemBufferMode(MemBuffer* const mem, MemBufferMode expected) {
+WEBP_NODISCARD static int CheckMemBufferMode(MemBuffer* const mem,
+                                             MemBufferMode expected) {
   if (mem->mode_ == MEM_MODE_NONE) {
     mem->mode_ = expected;    // switch to the expected mode
   } else if (mem->mode_ != expected) {
@@ -248,7 +253,7 @@ static int CheckMemBufferMode(MemBuffer* const mem, MemBufferMode expected) {
 }
 
 // To be called last.
-static VP8StatusCode FinishDecoding(WebPIDecoder* const idec) {
+WEBP_NODISCARD static VP8StatusCode FinishDecoding(WebPIDecoder* const idec) {
   const WebPDecoderOptions* const options = idec->params_.options;
   WebPDecBuffer* const output = idec->params_.output;
 
@@ -258,8 +263,10 @@ static VP8StatusCode FinishDecoding(WebPIDecoder* const idec) {
     if (status != VP8_STATUS_OK) return status;
   }
   if (idec->final_output_ != NULL) {
-    WebPCopyDecBufferPixels(output, idec->final_output_);  // do the slow-copy
+    const VP8StatusCode status = WebPCopyDecBufferPixels(
+        output, idec->final_output_);  // do the slow-copy
     WebPFreeDecBuffer(&idec->output_);
+    if (status != VP8_STATUS_OK) return status;
     *output = *idec->final_output_;
     idec->final_output_ = NULL;
   }
@@ -288,7 +295,7 @@ static void RestoreContext(const MBContext* context, VP8Decoder* const dec,
 static VP8StatusCode IDecError(WebPIDecoder* const idec, VP8StatusCode error) {
   if (idec->state_ == STATE_VP8_DATA) {
     // Synchronize the thread, clean-up and check for errors.
-    VP8ExitCritical((VP8Decoder*)idec->dec_, &idec->io_);
+    (void)VP8ExitCritical((VP8Decoder*)idec->dec_, &idec->io_);
   }
   idec->state_ = STATE_ERROR;
   return error;
@@ -602,8 +609,9 @@ static VP8StatusCode IDecode(WebPIDecoder* idec) {
 //------------------------------------------------------------------------------
 // Internal constructor
 
-static WebPIDecoder* NewDecoder(WebPDecBuffer* const output_buffer,
+WEBP_NODISCARD static WebPIDecoder* NewDecoder(
-                                const WebPBitstreamFeatures* const features) {
+    WebPDecBuffer* const output_buffer,
+    const WebPBitstreamFeatures* const features) {
   WebPIDecoder* idec = (WebPIDecoder*)WebPSafeCalloc(1ULL, sizeof(*idec));
   if (idec == NULL) {
     return NULL;
@@ -615,8 +623,10 @@ static WebPIDecoder* NewDecoder(WebPDecBuffer* const output_buffer,
   idec->last_mb_y_ = -1;
 
   InitMemBuffer(&idec->mem_);
-  WebPInitDecBuffer(&idec->output_);
+  if (!WebPInitDecBuffer(&idec->output_) || !VP8InitIo(&idec->io_)) {
-  VP8InitIo(&idec->io_);
+    WebPSafeFree(idec);
+    return NULL;
+  }
 
   WebPResetDecParams(&idec->params_);
   if (output_buffer == NULL || WebPAvoidSlowMemory(output_buffer, features)) {
@@ -675,7 +685,8 @@ void WebPIDelete(WebPIDecoder* idec) {
     if (!idec->is_lossless_) {
       if (idec->state_ == STATE_VP8_DATA) {
         // Synchronize the thread, clean-up and check for errors.
-        VP8ExitCritical((VP8Decoder*)idec->dec_, &idec->io_);
+        // TODO(vrabaud) do we care about the return result?
+        (void)VP8ExitCritical((VP8Decoder*)idec->dec_, &idec->io_);
       }
       VP8Delete((VP8Decoder*)idec->dec_);
     } else {
@@ -852,8 +863,8 @@ const WebPDecBuffer* WebPIDecodedArea(const WebPIDecoder* idec,
   return src;
 }
 
-uint8_t* WebPIDecGetRGB(const WebPIDecoder* idec, int* last_y,
+WEBP_NODISCARD uint8_t* WebPIDecGetRGB(const WebPIDecoder* idec, int* last_y,
-                        int* width, int* height, int* stride) {
+                                       int* width, int* height, int* stride) {
   const WebPDecBuffer* const src = GetOutputBuffer(idec);
   if (src == NULL) return NULL;
   if (src->colorspace >= MODE_YUV) {
@@ -868,10 +879,10 @@ uint8_t* WebPIDecGetRGB(const WebPIDecoder* idec, int* last_y,
   return src->u.RGBA.rgba;
 }
 
-uint8_t* WebPIDecGetYUVA(const WebPIDecoder* idec, int* last_y,
+WEBP_NODISCARD uint8_t* WebPIDecGetYUVA(const WebPIDecoder* idec, int* last_y,
-                         uint8_t** u, uint8_t** v, uint8_t** a,
+                                        uint8_t** u, uint8_t** v, uint8_t** a,
-                         int* width, int* height,
+                                        int* width, int* height, int* stride,
-                         int* stride, int* uv_stride, int* a_stride) {
+                                        int* uv_stride, int* a_stride) {
   const WebPDecBuffer* const src = GetOutputBuffer(idec);
   if (src == NULL) return NULL;
   if (src->colorspace < MODE_YUV) {

src/dec/vp8_dec.h

@@ -15,6 +15,7 @@
 #define WEBP_DEC_VP8_DEC_H_
 
 #include "src/webp/decode.h"
+#include "src/webp/types.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -108,16 +109,14 @@ struct VP8Io {
 };
 
 // Internal, version-checked, entry point
-int VP8InitIoInternal(VP8Io* const, int);
+WEBP_NODISCARD int VP8InitIoInternal(VP8Io* const, int);
 
 // Set the custom IO function pointers and user-data. The setter for IO hooks
 // should be called before initiating incremental decoding. Returns true if
 // WebPIDecoder object is successfully modified, false otherwise.
-int WebPISetIOHooks(WebPIDecoder* const idec,
+WEBP_NODISCARD int WebPISetIOHooks(WebPIDecoder* const idec, VP8IoPutHook put,
-                    VP8IoPutHook put,
+                                   VP8IoSetupHook setup,
-                    VP8IoSetupHook setup,
+                                   VP8IoTeardownHook teardown, void* user_data);
-                    VP8IoTeardownHook teardown,
-                    void* user_data);
 
 // Main decoding object. This is an opaque structure.
 typedef struct VP8Decoder VP8Decoder;
@@ -128,17 +127,17 @@ VP8Decoder* VP8New(void);
 // Must be called to make sure 'io' is initialized properly.
 // Returns false in case of version mismatch. Upon such failure, no other
 // decoding function should be called (VP8Decode, VP8GetHeaders, ...)
-static WEBP_INLINE int VP8InitIo(VP8Io* const io) {
+WEBP_NODISCARD static WEBP_INLINE int VP8InitIo(VP8Io* const io) {
   return VP8InitIoInternal(io, WEBP_DECODER_ABI_VERSION);
 }
 
 // Decode the VP8 frame header. Returns true if ok.
 // Note: 'io->data' must be pointing to the start of the VP8 frame header.
-int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io);
+WEBP_NODISCARD int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io);
 
 // Decode a picture. Will call VP8GetHeaders() if it wasn't done already.
 // Returns false in case of error.
-int VP8Decode(VP8Decoder* const dec, VP8Io* const io);
+WEBP_NODISCARD int VP8Decode(VP8Decoder* const dec, VP8Io* const io);
 
 // Return current status of the decoder:
 VP8StatusCode VP8Status(VP8Decoder* const dec);

src/dec/vp8i_dec.h

@@ -21,6 +21,7 @@
 #include "src/utils/random_utils.h"
 #include "src/utils/thread_utils.h"
 #include "src/dsp/dsp.h"
+#include "src/webp/types.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -282,7 +283,7 @@ int VP8ParseIntraModeRow(VP8BitReader* const br, VP8Decoder* const dec);
 void VP8ParseQuant(VP8Decoder* const dec);
 
 // in frame.c
-int VP8InitFrame(VP8Decoder* const dec, VP8Io* const io);
+WEBP_NODISCARD int VP8InitFrame(VP8Decoder* const dec, VP8Io* const io);
 // Call io->setup() and finish setting up scan parameters.
 // After this call returns, one must always call VP8ExitCritical() with the
 // same parameters. Both functions should be used in pair. Returns VP8_STATUS_OK
@@ -290,7 +291,7 @@ int VP8InitFrame(VP8Decoder* const dec, VP8Io* const io);
 VP8StatusCode VP8EnterCritical(VP8Decoder* const dec, VP8Io* const io);
 // Must always be called in pair with VP8EnterCritical().
 // Returns false in case of error.
-int VP8ExitCritical(VP8Decoder* const dec, VP8Io* const io);
+WEBP_NODISCARD int VP8ExitCritical(VP8Decoder* const dec, VP8Io* const io);
 // Return the multi-threading method to use (0=off), depending
 // on options and bitstream size. Only for lossy decoding.
 int VP8GetThreadMethod(const WebPDecoderOptions* const options,
@@ -300,11 +301,12 @@ int VP8GetThreadMethod(const WebPDecoderOptions* const options,
 void VP8InitDithering(const WebPDecoderOptions* const options,
                       VP8Decoder* const dec);
 // Process the last decoded row (filtering + output).
-int VP8ProcessRow(VP8Decoder* const dec, VP8Io* const io);
+WEBP_NODISCARD int VP8ProcessRow(VP8Decoder* const dec, VP8Io* const io);
 // To be called at the start of a new scanline, to initialize predictors.
 void VP8InitScanline(VP8Decoder* const dec);
 // Decode one macroblock. Returns false if there is not enough data.
-int VP8DecodeMB(VP8Decoder* const dec, VP8BitReader* const token_br);
+WEBP_NODISCARD int VP8DecodeMB(VP8Decoder* const dec,
+                               VP8BitReader* const token_br);
 
 // in alpha.c
 const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec,

src/dec/vp8li_dec.h

@@ -20,6 +20,7 @@
 #include "src/utils/bit_reader_utils.h"
 #include "src/utils/color_cache_utils.h"
 #include "src/utils/huffman_utils.h"
+#include "src/webp/types.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -99,25 +100,26 @@ struct ALPHDecoder;  // Defined in dec/alphai.h.
 
 // Decodes image header for alpha data stored using lossless compression.
 // Returns false in case of error.
-int VP8LDecodeAlphaHeader(struct ALPHDecoder* const alph_dec,
+WEBP_NODISCARD int VP8LDecodeAlphaHeader(struct ALPHDecoder* const alph_dec,
-                          const uint8_t* const data, size_t data_size);
+                                         const uint8_t* const data,
+                                         size_t data_size);
 
 // Decodes *at least* 'last_row' rows of alpha. If some of the initial rows are
 // already decoded in previous call(s), it will resume decoding from where it
 // was paused.
 // Returns false in case of bitstream error.
-int VP8LDecodeAlphaImageStream(struct ALPHDecoder* const alph_dec,
+WEBP_NODISCARD int VP8LDecodeAlphaImageStream(
-                               int last_row);
+    struct ALPHDecoder* const alph_dec, int last_row);
 
 // Allocates and initialize a new lossless decoder instance.
-VP8LDecoder* VP8LNew(void);
+WEBP_NODISCARD VP8LDecoder* VP8LNew(void);
 
 // Decodes the image header. Returns false in case of error.
-int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io);
+WEBP_NODISCARD int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io);
 
 // Decodes an image. It's required to decode the lossless header before calling
 // this function. Returns false in case of error, with updated dec->status_.
-int VP8LDecodeImage(VP8LDecoder* const dec);
+WEBP_NODISCARD int VP8LDecodeImage(VP8LDecoder* const dec);
 
 // Resets the decoder in its initial state, reclaiming memory.
 // Preserves the dec->status_ value.
@@ -133,11 +135,10 @@ void VP8LDelete(VP8LDecoder* const dec);
 // 'num_htree_groups' groups. If 'num_htree_groups_max' > 'num_htree_groups',
 // some of those indices map to -1. This is used for non-balanced codes to
 // limit memory usage.
-int ReadHuffmanCodesHelper(int color_cache_bits, int num_htree_groups,
+WEBP_NODISCARD int ReadHuffmanCodesHelper(
-                           int num_htree_groups_max, const int* const mapping,
+    int color_cache_bits, int num_htree_groups, int num_htree_groups_max,
-                           VP8LDecoder* const dec,
+    const int* const mapping, VP8LDecoder* const dec,
-                           HuffmanTables* const huffman_tables,
+    HuffmanTables* const huffman_tables, HTreeGroup** const htree_groups);
-                           HTreeGroup** const htree_groups);
 
 //------------------------------------------------------------------------------
 

src/dec/webp_dec.c

@@ -13,11 +13,14 @@
 
 #include <stdlib.h>
 
+#include "src/dec/vp8_dec.h"
 #include "src/dec/vp8i_dec.h"
 #include "src/dec/vp8li_dec.h"
 #include "src/dec/webpi_dec.h"
 #include "src/utils/utils.h"
 #include "src/webp/mux_types.h"  // ALPHA_FLAG
+#include "src/webp/decode.h"
+#include "src/webp/types.h"
 
 //------------------------------------------------------------------------------
 // RIFF layout is:
@@ -444,8 +447,9 @@ void WebPResetDecParams(WebPDecParams* const params) {
 // "Into" decoding variants
 
 // Main flow
-static VP8StatusCode DecodeInto(const uint8_t* const data, size_t data_size,
+WEBP_NODISCARD static VP8StatusCode DecodeInto(const uint8_t* const data,
-                                WebPDecParams* const params) {
+                                               size_t data_size,
+                                               WebPDecParams* const params) {
   VP8StatusCode status;
   VP8Io io;
   WebPHeaderStructure headers;
@@ -459,7 +463,9 @@ static VP8StatusCode DecodeInto(const uint8_t* const data, size_t data_size,
   }
 
   assert(params != NULL);
-  VP8InitIo(&io);
+  if (!VP8InitIo(&io)) {
+    return VP8_STATUS_INVALID_PARAM;
+  }
   io.data = headers.data + headers.offset;
   io.data_size = headers.data_size - headers.offset;
   WebPInitCustomIo(params, &io);  // Plug the I/O functions.
@@ -523,17 +529,16 @@ static VP8StatusCode DecodeInto(const uint8_t* const data, size_t data_size,
 }
 
 // Helpers
-static uint8_t* DecodeIntoRGBABuffer(WEBP_CSP_MODE colorspace,
+WEBP_NODISCARD static uint8_t* DecodeIntoRGBABuffer(WEBP_CSP_MODE colorspace,
-                                     const uint8_t* const data,
+                                                    const uint8_t* const data,
-                                     size_t data_size,
+                                                    size_t data_size,
-                                     uint8_t* const rgba,
+                                                    uint8_t* const rgba,
-                                     int stride, size_t size) {
+                                                    int stride, size_t size) {
   WebPDecParams params;
   WebPDecBuffer buf;
-  if (rgba == NULL) {
+  if (rgba == NULL || !WebPInitDecBuffer(&buf)) {
     return NULL;
   }
-  WebPInitDecBuffer(&buf);
   WebPResetDecParams(&params);
   params.output = &buf;
   buf.colorspace    = colorspace;
@@ -578,8 +583,7 @@ uint8_t* WebPDecodeYUVInto(const uint8_t* data, size_t data_size,
                            uint8_t* v, size_t v_size, int v_stride) {
   WebPDecParams params;
   WebPDecBuffer output;
-  if (luma == NULL) return NULL;
+  if (luma == NULL || !WebPInitDecBuffer(&output)) return NULL;
-  WebPInitDecBuffer(&output);
   WebPResetDecParams(&params);
   params.output = &output;
   output.colorspace      = MODE_YUV;
@@ -601,13 +605,17 @@ uint8_t* WebPDecodeYUVInto(const uint8_t* data, size_t data_size,
 
 //------------------------------------------------------------------------------
 
-static uint8_t* Decode(WEBP_CSP_MODE mode, const uint8_t* const data,
+WEBP_NODISCARD static uint8_t* Decode(WEBP_CSP_MODE mode,
-                       size_t data_size, int* const width, int* const height,
+                                      const uint8_t* const data,
-                       WebPDecBuffer* const keep_info) {
+                                      size_t data_size, int* const width,
+                                      int* const height,
+                                      WebPDecBuffer* const keep_info) {
   WebPDecParams params;
   WebPDecBuffer output;
 
-  WebPInitDecBuffer(&output);
+  if (!WebPInitDecBuffer(&output)) {
+    return NULL;
+  }
   WebPResetDecParams(&params);
   params.output = &output;
   output.colorspace = mode;
@@ -733,7 +741,9 @@ int WebPInitDecoderConfigInternal(WebPDecoderConfig* config,
   }
   memset(config, 0, sizeof(*config));
   DefaultFeatures(&config->input);
-  WebPInitDecBuffer(&config->output);
+  if (!WebPInitDecBuffer(&config->output)) {
+    return 0;
+  }
   return 1;
 }
 
@@ -772,7 +782,9 @@ VP8StatusCode WebPDecode(const uint8_t* data, size_t data_size,
   if (WebPAvoidSlowMemory(params.output, &config->input)) {
     // decoding to slow memory: use a temporary in-mem buffer to decode into.
     WebPDecBuffer in_mem_buffer;
-    WebPInitDecBuffer(&in_mem_buffer);
+    if (!WebPInitDecBuffer(&in_mem_buffer)) {
+      return VP8_STATUS_INVALID_PARAM;
+    }
     in_mem_buffer.colorspace = config->output.colorspace;
     in_mem_buffer.width = config->input.width;
     in_mem_buffer.height = config->input.height;

src/dec/webpi_dec.h

@@ -20,6 +20,7 @@ extern "C" {
 
 #include "src/utils/rescaler_utils.h"
 #include "src/dec/vp8_dec.h"
+#include "src/webp/decode.h"
 
 //------------------------------------------------------------------------------
 // WebPDecParams: Decoding output parameters. Transient internal object.
@@ -87,8 +88,9 @@ void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io);
 
 // Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers
 // to the *compressed* format, not the output one.
-int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
+WEBP_NODISCARD int WebPIoInitFromOptions(
-                          VP8Io* const io, WEBP_CSP_MODE src_colorspace);
+    const WebPDecoderOptions* const options, VP8Io* const io,
+    WEBP_CSP_MODE src_colorspace);
 
 //------------------------------------------------------------------------------
 // Internal functions regarding WebPDecBuffer memory (in buffer.c).

src/demux/anim_decode.c

@@ -20,6 +20,7 @@
 #include "src/utils/utils.h"
 #include "src/webp/decode.h"
 #include "src/webp/demux.h"
+#include "src/webp/types.h"
 
 #define NUM_CHANNELS 4
 
@@ -68,8 +69,9 @@ int WebPAnimDecoderOptionsInitInternal(WebPAnimDecoderOptions* dec_options,
   return 1;
 }
 
-static int ApplyDecoderOptions(const WebPAnimDecoderOptions* const dec_options,
+WEBP_NODISCARD static int ApplyDecoderOptions(
-                               WebPAnimDecoder* const dec) {
+    const WebPAnimDecoderOptions* const dec_options,
+    WebPAnimDecoder* const dec) {
   WEBP_CSP_MODE mode;
   WebPDecoderConfig* config = &dec->config_;
   assert(dec_options != NULL);
@@ -82,7 +84,9 @@ static int ApplyDecoderOptions(const WebPAnimDecoderOptions* const dec_options,
   dec->blend_func_ = (mode == MODE_RGBA || mode == MODE_BGRA)
                          ? &BlendPixelRowNonPremult
                          : &BlendPixelRowPremult;
-  WebPInitDecoderConfig(config);
+  if (!WebPInitDecoderConfig(config)) {
+    return 0;
+  }
   config->output.colorspace = mode;
   config->output.is_external_memory = 1;
   config->options.use_threads = dec_options->use_threads;
@@ -157,8 +161,8 @@ static int IsFullFrame(int width, int height, int canvas_width,
 }
 
 // Clear the canvas to transparent.
-static int ZeroFillCanvas(uint8_t* buf, uint32_t canvas_width,
+WEBP_NODISCARD static int ZeroFillCanvas(uint8_t* buf, uint32_t canvas_width,
-                          uint32_t canvas_height) {
+                                         uint32_t canvas_height) {
   const uint64_t size =
       (uint64_t)canvas_width * canvas_height * NUM_CHANNELS * sizeof(*buf);
   if (!CheckSizeOverflow(size)) return 0;
@@ -179,8 +183,8 @@ static void ZeroFillFrameRect(uint8_t* buf, int buf_stride, int x_offset,
 }
 
 // Copy width * height pixels from 'src' to 'dst'.
-static int CopyCanvas(const uint8_t* src, uint8_t* dst,
+WEBP_NODISCARD static int CopyCanvas(const uint8_t* src, uint8_t* dst,
-                      uint32_t width, uint32_t height) {
+                                     uint32_t width, uint32_t height) {
   const uint64_t size = (uint64_t)width * height * NUM_CHANNELS;
   if (!CheckSizeOverflow(size)) return 0;
   assert(src != NULL && dst != NULL);
@@ -424,7 +428,9 @@ int WebPAnimDecoderGetNext(WebPAnimDecoder* dec,
   WebPDemuxReleaseIterator(&dec->prev_iter_);
   dec->prev_iter_ = iter;
   dec->prev_frame_was_keyframe_ = is_key_frame;
-  CopyCanvas(dec->curr_frame_, dec->prev_frame_disposed_, width, height);
+  if (!CopyCanvas(dec->curr_frame_, dec->prev_frame_disposed_, width, height)) {
+    goto Error;
+  }
   if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
     ZeroFillFrameRect(dec->prev_frame_disposed_, width * NUM_CHANNELS,
                       dec->prev_iter_.x_offset, dec->prev_iter_.y_offset,

src/enc/alpha_enc.c

@@ -20,6 +20,7 @@
 #include "src/utils/filters_utils.h"
 #include "src/utils/quant_levels_utils.h"
 #include "src/utils/utils.h"
+#include "src/webp/encode.h"
 #include "src/webp/format_constants.h"
 
 // -----------------------------------------------------------------------------
@@ -66,7 +67,7 @@ static int EncodeLossless(const uint8_t* const data, int width, int height,
   WebPDispatchAlphaToGreen(data, width, picture.width, picture.height,
                            picture.argb, picture.argb_stride);
 
-  WebPConfigInit(&config);
+  if (!WebPConfigInit(&config)) return 0;
   config.lossless = 1;
   // Enable exact, or it would alter RGB values of transparent alpha, which is
   // normally OK but not here since we are not encoding the input image but  an

src/enc/vp8l_enc.c

@@ -1675,7 +1675,9 @@ int VP8LEncodeStream(const WebPConfig* const config,
   }
 
   // Avoid "garbage value" error from Clang's static analysis tool.
-  WebPPictureInit(&picture_side);
+  if (!WebPPictureInit(&picture_side)) {
+    goto Error;
+  }
 
   // Analyze image (entropy, num_palettes etc)
   if (!EncoderAnalyze(enc_main, crunch_configs, &num_crunch_configs_main,

src/mux/anim_encode.c

@@ -22,6 +22,7 @@
 #include "src/webp/encode.h"
 #include "src/webp/format_constants.h"
 #include "src/webp/mux.h"
+#include "src/webp/types.h"
 
 #if defined(_MSC_VER) && _MSC_VER < 1900
 #define snprintf _snprintf
@@ -1398,7 +1399,10 @@ int WebPAnimEncoderAdd(WebPAnimEncoder* enc, WebPPicture* frame, int timestamp,
     }
     config = *encoder_config;
   } else {
-    WebPConfigInit(&config);
+    if (!WebPConfigInit(&config)) {
+      MarkError(enc, "Cannot Init config");
+      return 0;
+    }
     config.lossless = 1;
   }
   assert(enc->curr_canvas_ == NULL);
@@ -1419,12 +1423,14 @@ int WebPAnimEncoderAdd(WebPAnimEncoder* enc, WebPPicture* frame, int timestamp,
 // -----------------------------------------------------------------------------
 // Bitstream assembly.
 
-static int DecodeFrameOntoCanvas(const WebPMuxFrameInfo* const frame,
+WEBP_NODISCARD static int DecodeFrameOntoCanvas(
-                                 WebPPicture* const canvas) {
+    const WebPMuxFrameInfo* const frame, WebPPicture* const canvas) {
   const WebPData* const image = &frame->bitstream;
   WebPPicture sub_image;
   WebPDecoderConfig config;
-  WebPInitDecoderConfig(&config);
+  if (!WebPInitDecoderConfig(&config)) {
+    return 0;
+  }
   WebPUtilClearPic(canvas, NULL);
   if (WebPGetFeatures(image->bytes, image->size, &config.input) !=
       VP8_STATUS_OK) {

src/utils/huffman_utils.h

@@ -63,7 +63,8 @@ typedef struct HuffmanTables {
 
 // Allocates a HuffmanTables with 'size' contiguous HuffmanCodes. Returns 0 on
 // memory allocation error, 1 otherwise.
-int VP8LHuffmanTablesAllocate(int size, HuffmanTables* huffman_tables);
+WEBP_NODISCARD int VP8LHuffmanTablesAllocate(int size,
+                                             HuffmanTables* huffman_tables);
 void VP8LHuffmanTablesDeallocate(HuffmanTables* const huffman_tables);
 
 #define HUFFMAN_PACKED_BITS 6
@@ -91,7 +92,7 @@ struct HTreeGroup {
 };
 
 // Creates the instance of HTreeGroup with specified number of tree-groups.
-HTreeGroup* VP8LHtreeGroupsNew(int num_htree_groups);
+WEBP_NODISCARD HTreeGroup* VP8LHtreeGroupsNew(int num_htree_groups);
 
 // Releases the memory allocated for HTreeGroup.
 void VP8LHtreeGroupsFree(HTreeGroup* const htree_groups);
@@ -101,8 +102,10 @@ void VP8LHtreeGroupsFree(HTreeGroup* const htree_groups);
 // the huffman table.
 // Returns built table size or 0 in case of error (invalid tree or
 // memory error).
-int VP8LBuildHuffmanTable(HuffmanTables* const root_table, int root_bits,
+WEBP_NODISCARD int VP8LBuildHuffmanTable(HuffmanTables* const root_table,
-                          const int code_lengths[], int code_lengths_size);
+                                         int root_bits,
+                                         const int code_lengths[],
+                                         int code_lengths_size);
 
 #ifdef __cplusplus
 }    // extern "C"

src/webp/decode.h

@@ -48,34 +48,33 @@ WEBP_EXTERN int WebPGetDecoderVersion(void);
 // RIFF + VP8X + (optional chunks) + VP8(L)
 // ALPH + VP8 <-- Not a valid WebP format: only allowed for internal purpose.
 // VP8(L)     <-- Not a valid WebP format: only allowed for internal purpose.
-WEBP_EXTERN int WebPGetInfo(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN int WebPGetInfo(
-                            int* width, int* height);
+    const uint8_t* data, size_t data_size, int* width, int* height);
 
 // Decodes WebP images pointed to by 'data' and returns RGBA samples, along
 // with the dimensions in *width and *height. The ordering of samples in
 // memory is R, G, B, A, R, G, B, A... in scan order (endian-independent).
 // The returned pointer should be deleted calling WebPFree().
 // Returns NULL in case of error.
-WEBP_EXTERN uint8_t* WebPDecodeRGBA(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeRGBA(
-                                    int* width, int* height);
+    const uint8_t* data, size_t data_size, int* width, int* height);
 
 // Same as WebPDecodeRGBA, but returning A, R, G, B, A, R, G, B... ordered data.
-WEBP_EXTERN uint8_t* WebPDecodeARGB(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeARGB(
-                                    int* width, int* height);
+    const uint8_t* data, size_t data_size, int* width, int* height);
 
 // Same as WebPDecodeRGBA, but returning B, G, R, A, B, G, R, A... ordered data.
-WEBP_EXTERN uint8_t* WebPDecodeBGRA(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeBGRA(
-                                    int* width, int* height);
+    const uint8_t* data, size_t data_size, int* width, int* height);
 
 // Same as WebPDecodeRGBA, but returning R, G, B, R, G, B... ordered data.
 // If the bitstream contains transparency, it is ignored.
-WEBP_EXTERN uint8_t* WebPDecodeRGB(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeRGB(
-                                   int* width, int* height);
+    const uint8_t* data, size_t data_size, int* width, int* height);
 
 // Same as WebPDecodeRGB, but returning B, G, R, B, G, R... ordered data.
-WEBP_EXTERN uint8_t* WebPDecodeBGR(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeBGR(
-                                   int* width, int* height);
+    const uint8_t* data, size_t data_size, int* width, int* height);
-
 
 // Decode WebP images pointed to by 'data' to Y'UV format(*). The pointer
 // returned is the Y samples buffer. Upon return, *u and *v will point to
@@ -87,10 +86,9 @@ WEBP_EXTERN uint8_t* WebPDecodeBGR(const uint8_t* data, size_t data_size,
 // 'width' and 'height' may be NULL, the other pointers must not be.
 // Returns NULL in case of error.
 // (*) Also named Y'CbCr. See: https://en.wikipedia.org/wiki/YCbCr
-WEBP_EXTERN uint8_t* WebPDecodeYUV(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeYUV(
-                                   int* width, int* height,
+    const uint8_t* data, size_t data_size, int* width, int* height,
-                                   uint8_t** u, uint8_t** v,
+    uint8_t** u, uint8_t** v, int* stride, int* uv_stride);
-                                   int* stride, int* uv_stride);
 
 // These five functions are variants of the above ones, that decode the image
 // directly into a pre-allocated buffer 'output_buffer'. The maximum storage
@@ -100,22 +98,22 @@ WEBP_EXTERN uint8_t* WebPDecodeYUV(const uint8_t* data, size_t data_size,
 // The parameter 'output_stride' specifies the distance (in bytes)
 // between scanlines. Hence, output_buffer_size is expected to be at least
 // output_stride x picture-height.
-WEBP_EXTERN uint8_t* WebPDecodeRGBAInto(
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeRGBAInto(
     const uint8_t* data, size_t data_size,
     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
-WEBP_EXTERN uint8_t* WebPDecodeARGBInto(
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeARGBInto(
     const uint8_t* data, size_t data_size,
     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
-WEBP_EXTERN uint8_t* WebPDecodeBGRAInto(
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeBGRAInto(
     const uint8_t* data, size_t data_size,
     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
 
 // RGB and BGR variants. Here too the transparency information, if present,
 // will be dropped and ignored.
-WEBP_EXTERN uint8_t* WebPDecodeRGBInto(
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeRGBInto(
     const uint8_t* data, size_t data_size,
     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
-WEBP_EXTERN uint8_t* WebPDecodeBGRInto(
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeBGRInto(
     const uint8_t* data, size_t data_size,
     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
 
@@ -126,7 +124,7 @@ WEBP_EXTERN uint8_t* WebPDecodeBGRInto(
 // 'u_size' and 'v_size' respectively.
 // Pointer to the luma plane ('*luma') is returned or NULL if an error occurred
 // during decoding (or because some buffers were found to be too small).
-WEBP_EXTERN uint8_t* WebPDecodeYUVInto(
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeYUVInto(
     const uint8_t* data, size_t data_size,
     uint8_t* luma, size_t luma_size, int luma_stride,
     uint8_t* u, size_t u_size, int u_stride,
@@ -217,11 +215,11 @@ struct WebPDecBuffer {
 };
 
 // Internal, version-checked, entry point
-WEBP_EXTERN int WebPInitDecBufferInternal(WebPDecBuffer*, int);
+WEBP_NODISCARD WEBP_EXTERN int WebPInitDecBufferInternal(WebPDecBuffer*, int);
 
 // Initialize the structure as empty. Must be called before any other use.
 // Returns false in case of version mismatch
-static WEBP_INLINE int WebPInitDecBuffer(WebPDecBuffer* buffer) {
+WEBP_NODISCARD static WEBP_INLINE int WebPInitDecBuffer(WebPDecBuffer* buffer) {
   return WebPInitDecBufferInternal(buffer, WEBP_DECODER_ABI_VERSION);
 }
 
@@ -232,7 +230,7 @@ WEBP_EXTERN void WebPFreeDecBuffer(WebPDecBuffer* buffer);
 //------------------------------------------------------------------------------
 // Enumeration of the status codes
 
-typedef enum VP8StatusCode {
+typedef enum WEBP_NODISCARD VP8StatusCode {
   VP8_STATUS_OK = 0,
   VP8_STATUS_OUT_OF_MEMORY,
   VP8_STATUS_INVALID_PARAM,
@@ -282,7 +280,8 @@ typedef enum VP8StatusCode {
 // within valid bounds.
 // All other fields of WebPDecBuffer MUST remain constant between calls.
 // Returns NULL if the allocation failed.
-WEBP_EXTERN WebPIDecoder* WebPINewDecoder(WebPDecBuffer* output_buffer);
+WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPINewDecoder(
+    WebPDecBuffer* output_buffer);
 
 // This function allocates and initializes an incremental-decoder object, which
 // will output the RGB/A samples specified by 'csp' into a preallocated
@@ -294,7 +293,7 @@ WEBP_EXTERN WebPIDecoder* WebPINewDecoder(WebPDecBuffer* output_buffer);
 // colorspace 'csp' is taken into account for allocating this buffer. All other
 // parameters are ignored.
 // Returns NULL if the allocation failed, or if some parameters are invalid.
-WEBP_EXTERN WebPIDecoder* WebPINewRGB(
+WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPINewRGB(
     WEBP_CSP_MODE csp,
     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
 
@@ -309,7 +308,7 @@ WEBP_EXTERN WebPIDecoder* WebPINewRGB(
 // In this case, the output buffer will be automatically allocated (using
 // MODE_YUVA) when decoding starts. All parameters are then ignored.
 // Returns NULL if the allocation failed or if a parameter is invalid.
-WEBP_EXTERN WebPIDecoder* WebPINewYUVA(
+WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPINewYUVA(
     uint8_t* luma, size_t luma_size, int luma_stride,
     uint8_t* u, size_t u_size, int u_stride,
     uint8_t* v, size_t v_size, int v_stride,
@@ -317,7 +316,7 @@ WEBP_EXTERN WebPIDecoder* WebPINewYUVA(
 
 // Deprecated version of the above, without the alpha plane.
 // Kept for backward compatibility.
-WEBP_EXTERN WebPIDecoder* WebPINewYUV(
+WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPINewYUV(
     uint8_t* luma, size_t luma_size, int luma_stride,
     uint8_t* u, size_t u_size, int u_stride,
     uint8_t* v, size_t v_size, int v_stride);
@@ -347,21 +346,21 @@ WEBP_EXTERN VP8StatusCode WebPIUpdate(
 // (*last_y, *width etc.) can be NULL if corresponding information is not
 // needed. The values in these pointers are only valid on successful (non-NULL)
 // return.
-WEBP_EXTERN uint8_t* WebPIDecGetRGB(
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPIDecGetRGB(
     const WebPIDecoder* idec, int* last_y,
     int* width, int* height, int* stride);
 
 // Same as above function to get a YUVA image. Returns pointer to the luma
 // plane or NULL in case of error. If there is no alpha information
 // the alpha pointer '*a' will be returned NULL.
-WEBP_EXTERN uint8_t* WebPIDecGetYUVA(
+WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPIDecGetYUVA(
     const WebPIDecoder* idec, int* last_y,
     uint8_t** u, uint8_t** v, uint8_t** a,
     int* width, int* height, int* stride, int* uv_stride, int* a_stride);
 
 // Deprecated alpha-less version of WebPIDecGetYUVA(): it will ignore the
 // alpha information (if present). Kept for backward compatibility.
-static WEBP_INLINE uint8_t* WebPIDecGetYUV(
+WEBP_NODISCARD static WEBP_INLINE uint8_t* WebPIDecGetYUV(
     const WebPIDecoder* idec, int* last_y, uint8_t** u, uint8_t** v,
     int* width, int* height, int* stride, int* uv_stride) {
   return WebPIDecGetYUVA(idec, last_y, u, v, NULL, width, height,
@@ -374,7 +373,7 @@ static WEBP_INLINE uint8_t* WebPIDecGetYUV(
 // Returns NULL in case the incremental decoder object is in an invalid state.
 // Otherwise returns the pointer to the internal representation. This structure
 // is read-only, tied to WebPIDecoder's lifespan and should not be modified.
-WEBP_EXTERN const WebPDecBuffer* WebPIDecodedArea(
+WEBP_NODISCARD WEBP_EXTERN const WebPDecBuffer* WebPIDecodedArea(
     const WebPIDecoder* idec, int* left, int* top, int* width, int* height);
 
 //------------------------------------------------------------------------------
@@ -469,12 +468,14 @@ struct WebPDecoderConfig {
 };
 
 // Internal, version-checked, entry point
-WEBP_EXTERN int WebPInitDecoderConfigInternal(WebPDecoderConfig*, int);
+WEBP_NODISCARD WEBP_EXTERN int WebPInitDecoderConfigInternal(WebPDecoderConfig*,
+                                                             int);
 
 // Initialize the configuration as empty. This function must always be
 // called first, unless WebPGetFeatures() is to be called.
 // Returns false in case of mismatched version.
-static WEBP_INLINE int WebPInitDecoderConfig(WebPDecoderConfig* config) {
+WEBP_NODISCARD static WEBP_INLINE int WebPInitDecoderConfig(
+    WebPDecoderConfig* config) {
   return WebPInitDecoderConfigInternal(config, WEBP_DECODER_ABI_VERSION);
 }
 
@@ -489,8 +490,8 @@ static WEBP_INLINE int WebPInitDecoderConfig(WebPDecoderConfig* config) {
 // The return WebPIDecoder object must always be deleted calling WebPIDelete().
 // Returns NULL in case of error (and config->status will then reflect
 // the error condition, if available).
-WEBP_EXTERN WebPIDecoder* WebPIDecode(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPIDecode(
-                                      WebPDecoderConfig* config);
+    const uint8_t* data, size_t data_size, WebPDecoderConfig* config);
 
 // Non-incremental version. This version decodes the full data at once, taking
 // 'config' into account. Returns decoding status (which should be VP8_STATUS_OK

src/webp/demux.h

@@ -50,6 +50,7 @@
 
 #include "./decode.h"     // for WEBP_CSP_MODE
 #include "./mux_types.h"
+#include "./types.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -85,13 +86,13 @@ typedef enum WebPDemuxState {
 } WebPDemuxState;
 
 // Internal, version-checked, entry point
-WEBP_EXTERN WebPDemuxer* WebPDemuxInternal(
+WEBP_NODISCARD WEBP_EXTERN WebPDemuxer* WebPDemuxInternal(
     const WebPData*, int, WebPDemuxState*, int);
 
 // Parses the full WebP file given by 'data'. For single images the WebP file
 // header alone or the file header and the chunk header may be absent.
 // Returns a WebPDemuxer object on successful parse, NULL otherwise.
-static WEBP_INLINE WebPDemuxer* WebPDemux(const WebPData* data) {
+WEBP_NODISCARD static WEBP_INLINE WebPDemuxer* WebPDemux(const WebPData* data) {
   return WebPDemuxInternal(data, 0, NULL, WEBP_DEMUX_ABI_VERSION);
 }
 
@@ -103,7 +104,7 @@ static WEBP_INLINE WebPDemuxer* WebPDemux(const WebPData* data) {
 // If this data is volatile, the demuxer object should be deleted (by calling
 // WebPDemuxDelete()) and WebPDemuxPartial() called again on the new data.
 // This is usually an inexpensive operation.
-static WEBP_INLINE WebPDemuxer* WebPDemuxPartial(
+WEBP_NODISCARD static WEBP_INLINE WebPDemuxer* WebPDemuxPartial(
     const WebPData* data, WebPDemuxState* state) {
   return WebPDemuxInternal(data, 1, state, WEBP_DEMUX_ABI_VERSION);
 }
@@ -164,14 +165,14 @@ struct WebPIterator {
 // Returns false if 'dmux' is NULL or frame 'frame_number' is not present.
 // Call WebPDemuxReleaseIterator() when use of the iterator is complete.
 // NOTE: 'dmux' must persist for the lifetime of 'iter'.
-WEBP_EXTERN int WebPDemuxGetFrame(
+WEBP_NODISCARD WEBP_EXTERN int WebPDemuxGetFrame(
     const WebPDemuxer* dmux, int frame_number, WebPIterator* iter);
 
 // Sets 'iter->fragment' to point to the next ('iter->frame_num' + 1) or
 // previous ('iter->frame_num' - 1) frame. These functions do not loop.
 // Returns true on success, false otherwise.
-WEBP_EXTERN int WebPDemuxNextFrame(WebPIterator* iter);
+WEBP_NODISCARD WEBP_EXTERN int WebPDemuxNextFrame(WebPIterator* iter);
-WEBP_EXTERN int WebPDemuxPrevFrame(WebPIterator* iter);
+WEBP_NODISCARD WEBP_EXTERN int WebPDemuxPrevFrame(WebPIterator* iter);
 
 // Releases any memory associated with 'iter'.
 // Must be called before any subsequent calls to WebPDemuxGetChunk() on the same
@@ -202,15 +203,16 @@ struct WebPChunkIterator {
 // payloads are accessed through WebPDemuxGetFrame() and related functions.
 // Call WebPDemuxReleaseChunkIterator() when use of the iterator is complete.
 // NOTE: 'dmux' must persist for the lifetime of the iterator.
-WEBP_EXTERN int WebPDemuxGetChunk(const WebPDemuxer* dmux,
+WEBP_NODISCARD WEBP_EXTERN int WebPDemuxGetChunk(const WebPDemuxer* dmux,
-                                  const char fourcc[4], int chunk_number,
+                                                 const char fourcc[4],
-                                  WebPChunkIterator* iter);
+                                                 int chunk_number,
+                                                 WebPChunkIterator* iter);
 
 // Sets 'iter->chunk' to point to the next ('iter->chunk_num' + 1) or previous
 // ('iter->chunk_num' - 1) chunk. These functions do not loop.
 // Returns true on success, false otherwise.
-WEBP_EXTERN int WebPDemuxNextChunk(WebPChunkIterator* iter);
+WEBP_NODISCARD WEBP_EXTERN int WebPDemuxNextChunk(WebPChunkIterator* iter);
-WEBP_EXTERN int WebPDemuxPrevChunk(WebPChunkIterator* iter);
+WEBP_NODISCARD WEBP_EXTERN int WebPDemuxPrevChunk(WebPChunkIterator* iter);
 
 // Releases any memory associated with 'iter'.
 // Must be called before destroying the associated WebPDemuxer with
@@ -257,21 +259,21 @@ struct WebPAnimDecoderOptions {
 };
 
 // Internal, version-checked, entry point.
-WEBP_EXTERN int WebPAnimDecoderOptionsInitInternal(
+WEBP_NODISCARD WEBP_EXTERN int WebPAnimDecoderOptionsInitInternal(
     WebPAnimDecoderOptions*, int);
 
 // Should always be called, to initialize a fresh WebPAnimDecoderOptions
 // structure before modification. Returns false in case of version mismatch.
 // WebPAnimDecoderOptionsInit() must have succeeded before using the
 // 'dec_options' object.
-static WEBP_INLINE int WebPAnimDecoderOptionsInit(
+WEBP_NODISCARD static WEBP_INLINE int WebPAnimDecoderOptionsInit(
     WebPAnimDecoderOptions* dec_options) {
   return WebPAnimDecoderOptionsInitInternal(dec_options,
                                             WEBP_DEMUX_ABI_VERSION);
 }
 
 // Internal, version-checked, entry point.
-WEBP_EXTERN WebPAnimDecoder* WebPAnimDecoderNewInternal(
+WEBP_NODISCARD WEBP_EXTERN WebPAnimDecoder* WebPAnimDecoderNewInternal(
     const WebPData*, const WebPAnimDecoderOptions*, int);
 
 // Creates and initializes a WebPAnimDecoder object.
@@ -284,7 +286,7 @@ WEBP_EXTERN WebPAnimDecoder* WebPAnimDecoderNewInternal(
 // Returns:
 //   A pointer to the newly created WebPAnimDecoder object, or NULL in case of
 //   parsing error, invalid option or memory error.
-static WEBP_INLINE WebPAnimDecoder* WebPAnimDecoderNew(
+WEBP_NODISCARD static WEBP_INLINE WebPAnimDecoder* WebPAnimDecoderNew(
     const WebPData* webp_data, const WebPAnimDecoderOptions* dec_options) {
   return WebPAnimDecoderNewInternal(webp_data, dec_options,
                                     WEBP_DEMUX_ABI_VERSION);
@@ -306,8 +308,8 @@ struct WebPAnimInfo {
 //   info - (out) global information fetched from the animation.
 // Returns:
 //   True on success.
-WEBP_EXTERN int WebPAnimDecoderGetInfo(const WebPAnimDecoder* dec,
+WEBP_NODISCARD WEBP_EXTERN int WebPAnimDecoderGetInfo(
-                                       WebPAnimInfo* info);
+    const WebPAnimDecoder* dec, WebPAnimInfo* info);
 
 // Fetch the next frame from 'dec' based on options supplied to
 // WebPAnimDecoderNew(). This will be a fully reconstructed canvas of size
@@ -321,8 +323,9 @@ WEBP_EXTERN int WebPAnimDecoderGetInfo(const WebPAnimDecoder* dec,
 // Returns:
 //   False if any of the arguments are NULL, or if there is a parsing or
 //   decoding error, or if there are no more frames. Otherwise, returns true.
-WEBP_EXTERN int WebPAnimDecoderGetNext(WebPAnimDecoder* dec,
+WEBP_NODISCARD WEBP_EXTERN int WebPAnimDecoderGetNext(WebPAnimDecoder* dec,
-                                       uint8_t** buf, int* timestamp);
+                                                      uint8_t** buf,
+                                                      int* timestamp);
 
 // Check if there are more frames left to decode.
 // Parameters:
@@ -330,7 +333,8 @@ WEBP_EXTERN int WebPAnimDecoderGetNext(WebPAnimDecoder* dec,
 // Returns:
 //   True if 'dec' is not NULL and some frames are yet to be decoded.
 //   Otherwise, returns false.
-WEBP_EXTERN int WebPAnimDecoderHasMoreFrames(const WebPAnimDecoder* dec);
+WEBP_NODISCARD WEBP_EXTERN int WebPAnimDecoderHasMoreFrames(
+    const WebPAnimDecoder* dec);
 
 // Resets the WebPAnimDecoder object, so that next call to
 // WebPAnimDecoderGetNext() will restart decoding from 1st frame. This would be
@@ -348,7 +352,7 @@ WEBP_EXTERN void WebPAnimDecoderReset(WebPAnimDecoder* dec);
 //
 // Parameters:
 //   dec - (in) decoder instance from which the demuxer object is to be fetched.
-WEBP_EXTERN const WebPDemuxer* WebPAnimDecoderGetDemuxer(
+WEBP_NODISCARD WEBP_EXTERN const WebPDemuxer* WebPAnimDecoderGetDemuxer(
     const WebPAnimDecoder* dec);
 
 // Deletes the WebPAnimDecoder object.

src/webp/encode.h

@@ -164,13 +164,14 @@ typedef enum WebPPreset {
 } WebPPreset;
 
 // Internal, version-checked, entry point
-WEBP_EXTERN int WebPConfigInitInternal(WebPConfig*, WebPPreset, float, int);
+WEBP_NODISCARD WEBP_EXTERN int WebPConfigInitInternal(WebPConfig*, WebPPreset,
+                                                      float, int);
 
 // Should always be called, to initialize a fresh WebPConfig structure before
 // modification. Returns false in case of version mismatch. WebPConfigInit()
 // must have succeeded before using the 'config' object.
 // Note that the default values are lossless=0 and quality=75.
-static WEBP_INLINE int WebPConfigInit(WebPConfig* config) {
+WEBP_NODISCARD static WEBP_INLINE int WebPConfigInit(WebPConfig* config) {
   return WebPConfigInitInternal(config, WEBP_PRESET_DEFAULT, 75.f,
                                 WEBP_ENCODER_ABI_VERSION);
 }
@@ -179,8 +180,9 @@ static WEBP_INLINE int WebPConfigInit(WebPConfig* config) {
 // set of parameters (referred to by 'preset') and a given quality factor.
 // This function can be called as a replacement to WebPConfigInit(). Will
 // return false in case of error.
-static WEBP_INLINE int WebPConfigPreset(WebPConfig* config,
+WEBP_NODISCARD static WEBP_INLINE int WebPConfigPreset(WebPConfig* config,
-                                        WebPPreset preset, float quality) {
+                                                       WebPPreset preset,
+                                                       float quality) {
   return WebPConfigInitInternal(config, preset, quality,
                                 WEBP_ENCODER_ABI_VERSION);
 }
@@ -191,11 +193,12 @@ static WEBP_INLINE int WebPConfigPreset(WebPConfig* config,
 // speed and final compressed size.
 // This function will overwrite several fields from config: 'method', 'quality'
 // and 'lossless'. Returns false in case of parameter error.
-WEBP_EXTERN int WebPConfigLosslessPreset(WebPConfig* config, int level);
+WEBP_NODISCARD WEBP_EXTERN int WebPConfigLosslessPreset(WebPConfig* config,
+                                                        int level);
 
 // Returns true if 'config' is non-NULL and all configuration parameters are
 // within their valid ranges.
-WEBP_EXTERN int WebPValidateConfig(const WebPConfig* config);
+WEBP_NODISCARD WEBP_EXTERN int WebPValidateConfig(const WebPConfig* config);
 
 //------------------------------------------------------------------------------
 // Input / Output
@@ -255,8 +258,8 @@ WEBP_EXTERN void WebPMemoryWriterClear(WebPMemoryWriter* writer);
 // The custom writer to be used with WebPMemoryWriter as custom_ptr. Upon
 // completion, writer.mem and writer.size will hold the coded data.
 // writer.mem must be freed by calling WebPMemoryWriterClear.
-WEBP_EXTERN int WebPMemoryWrite(const uint8_t* data, size_t data_size,
+WEBP_NODISCARD WEBP_EXTERN int WebPMemoryWrite(
-                                const WebPPicture* picture);
+    const uint8_t* data, size_t data_size, const WebPPicture* picture);
 
 // Progress hook, called from time to time to report progress. It can return
 // false to request an abort of the encoding process, or true otherwise if
@@ -364,13 +367,13 @@ struct WebPPicture {
 };
 
 // Internal, version-checked, entry point
-WEBP_EXTERN int WebPPictureInitInternal(WebPPicture*, int);
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureInitInternal(WebPPicture*, int);
 
 // Should always be called, to initialize the structure. Returns false in case
 // of version mismatch. WebPPictureInit() must have succeeded before using the
 // 'picture' object.
 // Note that, by default, use_argb is false and colorspace is WEBP_YUV420.
-static WEBP_INLINE int WebPPictureInit(WebPPicture* picture) {
+WEBP_NODISCARD static WEBP_INLINE int WebPPictureInit(WebPPicture* picture) {
   return WebPPictureInitInternal(picture, WEBP_ENCODER_ABI_VERSION);
 }
 
@@ -381,7 +384,7 @@ static WEBP_INLINE int WebPPictureInit(WebPPicture* picture) {
 // Allocate y/u/v buffers as per colorspace/width/height specification.
 // Note! This function will free the previous buffer if needed.
 // Returns false in case of memory error.
-WEBP_EXTERN int WebPPictureAlloc(WebPPicture* picture);
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureAlloc(WebPPicture* picture);
 
 // Release the memory allocated by WebPPictureAlloc() or WebPPictureImport*().
 // Note that this function does _not_ free the memory used by the 'picture'
@@ -394,7 +397,8 @@ WEBP_EXTERN void WebPPictureFree(WebPPicture* picture);
 // will fully own the copied pixels (this is not a view). The 'dst' picture need
 // not be initialized as its content is overwritten.
 // Returns false in case of memory allocation error.
-WEBP_EXTERN int WebPPictureCopy(const WebPPicture* src, WebPPicture* dst);
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureCopy(const WebPPicture* src,
+                                               WebPPicture* dst);
 
 // Compute the single distortion for packed planes of samples.
 // 'src' will be compared to 'ref', and the raw distortion stored into
@@ -403,19 +407,18 @@ WEBP_EXTERN int WebPPictureCopy(const WebPPicture* src, WebPPicture* dst);
 // 'x_step' is the horizontal stride (in bytes) between samples.
 // 'src/ref_stride' is the byte distance between rows.
 // Returns false in case of error (bad parameter, memory allocation error, ...).
-WEBP_EXTERN int WebPPlaneDistortion(const uint8_t* src, size_t src_stride,
+WEBP_NODISCARD WEBP_EXTERN int WebPPlaneDistortion(
-                                    const uint8_t* ref, size_t ref_stride,
+    const uint8_t* src, size_t src_stride,
-                                    int width, int height,
+    const uint8_t* ref, size_t ref_stride, int width, int height, size_t x_step,
-                                    size_t x_step,
+    int type,  // 0 = PSNR, 1 = SSIM, 2 = LSIM
-                                    int type,   // 0 = PSNR, 1 = SSIM, 2 = LSIM
+    float* distortion, float* result);
-                                    float* distortion, float* result);
 
 // Compute PSNR, SSIM or LSIM distortion metric between two pictures. Results
 // are in dB, stored in result[] in the B/G/R/A/All order. The distortion is
 // always performed using ARGB samples. Hence if the input is YUV(A), the
 // picture will be internally converted to ARGB (just for the measurement).
 // Warning: this function is rather CPU-intensive.
-WEBP_EXTERN int WebPPictureDistortion(
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureDistortion(
     const WebPPicture* src, const WebPPicture* ref,
     int metric_type,           // 0 = PSNR, 1 = SSIM, 2 = LSIM
     float result[5]);
@@ -428,8 +431,8 @@ WEBP_EXTERN int WebPPictureDistortion(
 // must be fully be comprised inside the 'src' source picture. If the source
 // picture uses the YUV420 colorspace, the top and left coordinates will be
 // snapped to even values.
-WEBP_EXTERN int WebPPictureCrop(WebPPicture* picture,
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureCrop(
-                                int left, int top, int width, int height);
+    WebPPicture* picture, int left, int top, int width, int height);
 
 // Extracts a view from 'src' picture into 'dst'. The rectangle for the view
 // is defined by the top-left corner pixel coordinates (left, top) as well
@@ -442,9 +445,9 @@ WEBP_EXTERN int WebPPictureCrop(WebPPicture* picture,
 // with WebPPictureInit() if it is different from 'src', since its content will
 // be overwritten.
 // Returns false in case of invalid parameters.
-WEBP_EXTERN int WebPPictureView(const WebPPicture* src,
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureView(
-                                int left, int top, int width, int height,
+    const WebPPicture* src, int left, int top, int width, int height,
-                                WebPPicture* dst);
+    WebPPicture* dst);
 
 // Returns true if the 'picture' is actually a view and therefore does
 // not own the memory for pixels.
@@ -455,29 +458,30 @@ WEBP_EXTERN int WebPPictureIsView(const WebPPicture* picture);
 // dimension will be calculated preserving the aspect ratio.
 // No gamma correction is applied.
 // Returns false in case of error (invalid parameter or insufficient memory).
-WEBP_EXTERN int WebPPictureRescale(WebPPicture* picture, int width, int height);
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureRescale(WebPPicture* picture,
+                                                  int width, int height);
 
 // Colorspace conversion function to import RGB samples.
 // Previous buffer will be free'd, if any.
 // *rgb buffer should have a size of at least height * rgb_stride.
 // Returns false in case of memory error.
-WEBP_EXTERN int WebPPictureImportRGB(
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportRGB(
     WebPPicture* picture, const uint8_t* rgb, int rgb_stride);
 // Same, but for RGBA buffer.
-WEBP_EXTERN int WebPPictureImportRGBA(
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportRGBA(
     WebPPicture* picture, const uint8_t* rgba, int rgba_stride);
 // Same, but for RGBA buffer. Imports the RGB direct from the 32-bit format
 // input buffer ignoring the alpha channel. Avoids needing to copy the data
 // to a temporary 24-bit RGB buffer to import the RGB only.
-WEBP_EXTERN int WebPPictureImportRGBX(
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportRGBX(
     WebPPicture* picture, const uint8_t* rgbx, int rgbx_stride);
 
 // Variants of the above, but taking BGR(A|X) input.
-WEBP_EXTERN int WebPPictureImportBGR(
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportBGR(
     WebPPicture* picture, const uint8_t* bgr, int bgr_stride);
-WEBP_EXTERN int WebPPictureImportBGRA(
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportBGRA(
     WebPPicture* picture, const uint8_t* bgra, int bgra_stride);
-WEBP_EXTERN int WebPPictureImportBGRX(
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportBGRX(
     WebPPicture* picture, const uint8_t* bgrx, int bgrx_stride);
 
 // Converts picture->argb data to the YUV420A format. The 'colorspace'
@@ -486,24 +490,24 @@ WEBP_EXTERN int WebPPictureImportBGRX(
 // non-opaque transparent values is detected, and 'colorspace' will be
 // adjusted accordingly. Note that this method is lossy.
 // Returns false in case of error.
-WEBP_EXTERN int WebPPictureARGBToYUVA(WebPPicture* picture,
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureARGBToYUVA(
-                                      WebPEncCSP /*colorspace = WEBP_YUV420*/);
+    WebPPicture* picture, WebPEncCSP /*colorspace = WEBP_YUV420*/);
 
 // Same as WebPPictureARGBToYUVA(), but the conversion is done using
 // pseudo-random dithering with a strength 'dithering' between
 // 0.0 (no dithering) and 1.0 (maximum dithering). This is useful
 // for photographic picture.
-WEBP_EXTERN int WebPPictureARGBToYUVADithered(
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureARGBToYUVADithered(
     WebPPicture* picture, WebPEncCSP colorspace, float dithering);
 
-// Performs 'sharp' RGBA->YUVA420 downsampling and colorspace conversion.
+// Performs 'sharp' RGBA->YUVA420 downsampling and colorspace conversion
 // Downsampling is handled with extra care in case of color clipping. This
 // method is roughly 2x slower than WebPPictureARGBToYUVA() but produces better
 // and sharper YUV representation.
 // Returns false in case of error.
-WEBP_EXTERN int WebPPictureSharpARGBToYUVA(WebPPicture* picture);
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureSharpARGBToYUVA(WebPPicture* picture);
 // kept for backward compatibility:
-WEBP_EXTERN int WebPPictureSmartARGBToYUVA(WebPPicture* picture);
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureSmartARGBToYUVA(WebPPicture* picture);
 
 // Converts picture->yuv to picture->argb and sets picture->use_argb to true.
 // The input format must be YUV_420 or YUV_420A. The conversion from YUV420 to
@@ -511,7 +515,7 @@ WEBP_EXTERN int WebPPictureSmartARGBToYUVA(WebPPicture* picture);
 // Note that the use of this colorspace is discouraged if one has access to the
 // raw ARGB samples, since using YUV420 is comparatively lossy.
 // Returns false in case of error.
-WEBP_EXTERN int WebPPictureYUVAToARGB(WebPPicture* picture);
+WEBP_NODISCARD WEBP_EXTERN int WebPPictureYUVAToARGB(WebPPicture* picture);
 
 // Helper function: given a width x height plane of RGBA or YUV(A) samples
 // clean-up or smoothen the YUV or RGB samples under fully transparent area,
@@ -541,7 +545,8 @@ WEBP_EXTERN void WebPBlendAlpha(WebPPicture* picture, uint32_t background_rgb);
 // the former for lossy encoding, and the latter for lossless encoding
 // (when config.lossless is true). Automatic conversion from one format to
 // another is provided but they both incur some loss.
-WEBP_EXTERN int WebPEncode(const WebPConfig* config, WebPPicture* picture);
+WEBP_NODISCARD WEBP_EXTERN int WebPEncode(const WebPConfig* config,
+                                          WebPPicture* picture);
 
 //------------------------------------------------------------------------------
 

src/webp/mux.h

@@ -16,6 +16,7 @@
 #define WEBP_WEBP_MUX_H_
 
 #include "./mux_types.h"
+#include "./types.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -70,7 +71,7 @@ typedef struct WebPMuxAnimParams WebPMuxAnimParams;
 typedef struct WebPAnimEncoderOptions WebPAnimEncoderOptions;
 
 // Error codes
-typedef enum WebPMuxError {
+typedef enum WEBP_NODISCARD WebPMuxError {
   WEBP_MUX_OK                 =  1,
   WEBP_MUX_NOT_FOUND          =  0,
   WEBP_MUX_INVALID_ARGUMENT   = -1,
@@ -104,13 +105,13 @@ WEBP_EXTERN int WebPGetMuxVersion(void);
 // Life of a Mux object
 
 // Internal, version-checked, entry point
-WEBP_EXTERN WebPMux* WebPNewInternal(int);
+WEBP_NODISCARD WEBP_EXTERN WebPMux* WebPNewInternal(int);
 
 // Creates an empty mux object.
 // Returns:
 //   A pointer to the newly created empty mux object.
 //   Or NULL in case of memory error.
-static WEBP_INLINE WebPMux* WebPMuxNew(void) {
+WEBP_NODISCARD static WEBP_INLINE WebPMux* WebPMuxNew(void) {
   return WebPNewInternal(WEBP_MUX_ABI_VERSION);
 }
 
@@ -123,7 +124,8 @@ WEBP_EXTERN void WebPMuxDelete(WebPMux* mux);
 // Mux creation.
 
 // Internal, version-checked, entry point
-WEBP_EXTERN WebPMux* WebPMuxCreateInternal(const WebPData*, int, int);
+WEBP_NODISCARD WEBP_EXTERN WebPMux* WebPMuxCreateInternal(const WebPData*, int,
+                                                          int);
 
 // Creates a mux object from raw data given in WebP RIFF format.
 // Parameters:
@@ -133,8 +135,8 @@ WEBP_EXTERN WebPMux* WebPMuxCreateInternal(const WebPData*, int, int);
 // Returns:
 //   A pointer to the mux object created from given data - on success.
 //   NULL - In case of invalid data or memory error.
-static WEBP_INLINE WebPMux* WebPMuxCreate(const WebPData* bitstream,
+WEBP_NODISCARD static WEBP_INLINE WebPMux* WebPMuxCreate(
-                                          int copy_data) {
+    const WebPData* bitstream, int copy_data) {
   return WebPMuxCreateInternal(bitstream, copy_data, WEBP_MUX_ABI_VERSION);
 }
 
@@ -449,7 +451,7 @@ WEBP_EXTERN int WebPAnimEncoderOptionsInitInternal(
 // structure before modification. Returns false in case of version mismatch.
 // WebPAnimEncoderOptionsInit() must have succeeded before using the
 // 'enc_options' object.
-static WEBP_INLINE int WebPAnimEncoderOptionsInit(
+WEBP_NODISCARD static WEBP_INLINE int WebPAnimEncoderOptionsInit(
     WebPAnimEncoderOptions* enc_options) {
   return WebPAnimEncoderOptionsInitInternal(enc_options, WEBP_MUX_ABI_VERSION);
 }
@@ -490,7 +492,7 @@ static WEBP_INLINE WebPAnimEncoder* WebPAnimEncoderNew(
 // Returns:
 //   On error, returns false and frame->error_code is set appropriately.
 //   Otherwise, returns true.
-WEBP_EXTERN int WebPAnimEncoderAdd(
+WEBP_NODISCARD WEBP_EXTERN int WebPAnimEncoderAdd(
     WebPAnimEncoder* enc, struct WebPPicture* frame, int timestamp_ms,
     const struct WebPConfig* config);
 
@@ -503,8 +505,8 @@ WEBP_EXTERN int WebPAnimEncoderAdd(
 //   webp_data - (out) generated WebP bitstream.
 // Returns:
 //   True on success.
-WEBP_EXTERN int WebPAnimEncoderAssemble(WebPAnimEncoder* enc,
+WEBP_NODISCARD WEBP_EXTERN int WebPAnimEncoderAssemble(WebPAnimEncoder* enc,
-                                        WebPData* webp_data);
+                                                       WebPData* webp_data);
 
 // Get error string corresponding to the most recent call using 'enc'. The
 // returned string is owned by 'enc' and is valid only until the next call to

src/webp/mux_types.h

@@ -79,7 +79,8 @@ static WEBP_INLINE void WebPDataClear(WebPData* webp_data) {
 
 // Allocates necessary storage for 'dst' and copies the contents of 'src'.
 // Returns true on success.
-static WEBP_INLINE int WebPDataCopy(const WebPData* src, WebPData* dst) {
+WEBP_NODISCARD static WEBP_INLINE int WebPDataCopy(const WebPData* src,
+                                                   WebPData* dst) {
   if (src == NULL || dst == NULL) return 0;
   WebPDataInit(dst);
   if (src->bytes != NULL && src->size != 0) {

src/webp/types.h

@@ -36,6 +36,23 @@ typedef long long int int64_t;
 #define WEBP_INLINE __forceinline
 #endif  /* _MSC_VER */
 
+#if defined(WEBP_ENABLE_NODISCARD) ||                   \
+    (defined(__cplusplus) && __cplusplus >= 201700L) || \
+    (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L)
+#define WEBP_NODISCARD [[nodiscard]]
+#else
+// gcc's __has_attribute does not work for enums.
+#if defined(__clang__) && defined(__has_attribute)
+#if __has_attribute(warn_unused_result)
+#define WEBP_NODISCARD __attribute__((warn_unused_result))
+#else
+#define WEBP_NODISCARD
+#endif
+#else
+#define WEBP_NODISCARD
+#endif
+#endif
+
 #ifndef WEBP_EXTERN
 // This explicitly marks library functions and allows for changing the
 // signature for e.g., Windows DLL builds.
@@ -60,7 +77,7 @@ extern "C" {
 // Allocates 'size' bytes of memory. Returns NULL upon error. Memory
 // must be deallocated by calling WebPFree(). This function is made available
 // by the core 'libwebp' library.
-WEBP_EXTERN void* WebPMalloc(size_t size);
+WEBP_NODISCARD WEBP_EXTERN void* WebPMalloc(size_t size);
 
 // Releases memory returned by the WebPDecode*() functions (from decode.h).
 WEBP_EXTERN void WebPFree(void* ptr);

tests/fuzzer/advanced_api_fuzzer.c

@@ -130,7 +130,7 @@ int LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size) {
       }
       WebPIDelete(idec);
     } else {
-      WebPDecode(data, size, &config);
+      (void)WebPDecode(data, size, &config);
     }
 
     WebPFreeDecBuffer(&config.output);

tests/fuzzer/huffman_fuzzer.c

@@ -52,9 +52,9 @@ int LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size) {
   if (num_htree_groups == 0) goto Error;
   // This variable is only useful when mapping is not NULL.
   const int num_htree_groups_max = num_htree_groups;
-  ReadHuffmanCodesHelper(color_cache_bits, num_htree_groups,
+  (void)ReadHuffmanCodesHelper(color_cache_bits, num_htree_groups,
-                         num_htree_groups_max, mapping, dec, &huffman_tables,
+                               num_htree_groups_max, mapping, dec,
-                         &htree_groups);
+                               &huffman_tables, &htree_groups);
 
  Error:
   WebPSafeFree(mapping);

tests/fuzzer/mux_demux_api_fuzzer.c

@@ -33,15 +33,15 @@ int LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size) {
     if (!mux) return 0;
 
     WebPData chunk;
-    WebPMuxGetChunk(mux, "EXIF", &chunk);
+    (void)WebPMuxGetChunk(mux, "EXIF", &chunk);
-    WebPMuxGetChunk(mux, "ICCP", &chunk);
+    (void)WebPMuxGetChunk(mux, "ICCP", &chunk);
-    WebPMuxGetChunk(mux, "FUZZ", &chunk);  // unknown
+    (void)WebPMuxGetChunk(mux, "FUZZ", &chunk);  // unknown
 
     uint32_t flags;
-    WebPMuxGetFeatures(mux, &flags);
+    (void)WebPMuxGetFeatures(mux, &flags);
 
     WebPMuxAnimParams params;
-    WebPMuxGetAnimationParams(mux, &params);
+    (void)WebPMuxGetAnimationParams(mux, &params);
 
     WebPMuxError status;
     WebPMuxFrameInfo info;
@@ -72,11 +72,11 @@ int LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size) {
 
     WebPChunkIterator chunk_iter;
     if (WebPDemuxGetChunk(demux, "EXIF", 1, &chunk_iter)) {
-      WebPDemuxNextChunk(&chunk_iter);
+      (void)WebPDemuxNextChunk(&chunk_iter);
     }
     WebPDemuxReleaseChunkIterator(&chunk_iter);
     if (WebPDemuxGetChunk(demux, "ICCP", 0, &chunk_iter)) {  // 0 == last
-      WebPDemuxPrevChunk(&chunk_iter);
+      (void)WebPDemuxPrevChunk(&chunk_iter);
     }
     WebPDemuxReleaseChunkIterator(&chunk_iter);
     // Skips FUZZ because the Demux API has no concept of (un)known chunks.

tests/fuzzer/simple_api_fuzzer.c

@@ -49,17 +49,17 @@ int LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size) {
     if (value % 0x10 == 0) buf_size--;
     uint8_t* const ext_buf = (uint8_t*)malloc(buf_size);
     if (value < 0x94) {
-      WebPDecodeRGBAInto(data, size, ext_buf, buf_size, stride);
+      (void)WebPDecodeRGBAInto(data, size, ext_buf, buf_size, stride);
 #if !defined(WEBP_REDUCE_CSP)
     } else if (value < 0xa9) {
-      WebPDecodeARGBInto(data, size, ext_buf, buf_size, stride);
+      (void)WebPDecodeARGBInto(data, size, ext_buf, buf_size, stride);
     } else if (value < 0xbe) {
-      WebPDecodeBGRInto(data, size, ext_buf, buf_size, stride);
+      (void)WebPDecodeBGRInto(data, size, ext_buf, buf_size, stride);
     } else if (value < 0xd3) {
-      WebPDecodeRGBInto(data, size, ext_buf, buf_size, stride);
+      (void)WebPDecodeRGBInto(data, size, ext_buf, buf_size, stride);
 #endif  // !defined(WEBP_REDUCE_CSP)
     } else {
-      WebPDecodeBGRAInto(data, size, ext_buf, buf_size, stride);
+      (void)WebPDecodeBGRAInto(data, size, ext_buf, buf_size, stride);
     }
     free(ext_buf);
   } else {
@@ -75,8 +75,9 @@ int LLVMFuzzerTestOneInput(const uint8_t* const data, size_t size) {
     uint8_t* const luma_buf = (uint8_t*)malloc(luma_size);
     uint8_t* const u_buf = (uint8_t*)malloc(u_size);
     uint8_t* const v_buf = (uint8_t*)malloc(v_size);
-    WebPDecodeYUVInto(data, size, luma_buf, luma_size, w /* luma_stride */,
+    (void)WebPDecodeYUVInto(data, size, luma_buf, luma_size,
-                      u_buf, u_size, uv_stride, v_buf, v_size, uv_stride);
+                            w /* luma_stride */, u_buf, u_size, uv_stride,
+                            v_buf, v_size, uv_stride);
     free(luma_buf);
     free(u_buf);
     free(v_buf);