Remove some errors when compiling the code as C++.

This fixes some cases from
https://bugs.chromium.org/p/webp/issues/detail?id=137

Change-Id: I58f3a617bf973dbe4c5794004a01e2aea39ba53a
(cherry picked from commit 28ce304344)

src/dec/alpha.c

@@ -67,7 +67,7 @@ static int ALPHInit(ALPHDecoder* const dec, const uint8_t* data,
   }
 
   dec->method_ = (data[0] >> 0) & 0x03;
-  dec->filter_ = (data[0] >> 2) & 0x03;
+  dec->filter_ = (WEBP_FILTER_TYPE)((data[0] >> 2) & 0x03);
   dec->pre_processing_ = (data[0] >> 4) & 0x03;
   rsrv = (data[0] >> 6) & 0x03;
   if (dec->method_ < ALPHA_NO_COMPRESSION ||

src/demux/anim_decode.c

@@ -113,10 +113,10 @@ WebPAnimDecoder* WebPAnimDecoderNewInternal(
   dec->info_.frame_count = WebPDemuxGetI(dec->demux_, WEBP_FF_FRAME_COUNT);
 
   // Note: calloc() because we fill frame with zeroes as well.
-  dec->curr_frame_ = WebPSafeCalloc(
+  dec->curr_frame_ = (uint8_t*)WebPSafeCalloc(
       dec->info_.canvas_width * NUM_CHANNELS, dec->info_.canvas_height);
   if (dec->curr_frame_ == NULL) goto Error;
-  dec->prev_frame_disposed_ = WebPSafeCalloc(
+  dec->prev_frame_disposed_ = (uint8_t*)WebPSafeCalloc(
       dec->info_.canvas_width * NUM_CHANNELS, dec->info_.canvas_height);
   if (dec->prev_frame_disposed_ == NULL) goto Error;
 

src/dsp/dec.c

@@ -239,7 +239,7 @@ VP8PredFunc VP8PredLuma16[NUM_B_DC_MODES];
 //------------------------------------------------------------------------------
 // 4x4
 
-#define AVG3(a, b, c) (((a) + 2 * (b) + (c) + 2) >> 2)
+#define AVG3(a, b, c) ((uint8_t)(((a) + 2 * (b) + (c) + 2) >> 2))
 #define AVG2(a, b) (((a) + (b) + 1) >> 1)
 
 static void VE4(uint8_t* dst) {    // vertical

src/dsp/enc.c

@@ -335,7 +335,7 @@ static void Intra16Preds(uint8_t* dst,
 // luma 4x4 prediction
 
 #define DST(x, y) dst[(x) + (y) * BPS]
-#define AVG3(a, b, c) (((a) + 2 * (b) + (c) + 2) >> 2)
+#define AVG3(a, b, c) ((uint8_t)(((a) + 2 * (b) + (c) + 2) >> 2))
 #define AVG2(a, b) (((a) + (b) + 1) >> 1)
 
 static void VE4(uint8_t* dst, const uint8_t* top) {    // vertical

src/enc/histogram.c

@@ -592,8 +592,8 @@ static int HistoQueueInit(HistoQueue* const histo_queue, const int max_index) {
   histo_queue->max_size = max_index * max_index;
   // We allocate max_size + 1 because the last element at index "size" is
   // used as temporary data (and it could be up to max_size).
-  histo_queue->queue = WebPSafeMalloc(histo_queue->max_size + 1,
-                                      sizeof(*histo_queue->queue));
+  histo_queue->queue = (HistogramPair*)WebPSafeMalloc(
+      histo_queue->max_size + 1, sizeof(*histo_queue->queue));
   return histo_queue->queue != NULL;
 }
 
@@ -659,7 +659,8 @@ static int HistogramCombineGreedy(VP8LHistogramSet* const image_histo) {
   int i, j;
   VP8LHistogram** const histograms = image_histo->histograms;
   // Indexes of remaining histograms.
-  int* const clusters = WebPSafeMalloc(image_histo_size, sizeof(*clusters));
+  int* const clusters =
+      (int*)WebPSafeMalloc(image_histo_size, sizeof(*clusters));
   // Priority queue of histogram pairs.
   HistoQueue histo_queue;
 

src/enc/picture.c

@@ -88,8 +88,9 @@ int WebPPictureAllocARGB(WebPPicture* const picture, int width, int height) {
 }
 
 int WebPPictureAllocYUVA(WebPPicture* const picture, int width, int height) {
-  const WebPEncCSP uv_csp = picture->colorspace & WEBP_CSP_UV_MASK;
-  const int has_alpha = picture->colorspace & WEBP_CSP_ALPHA_BIT;
+  const WebPEncCSP uv_csp =
+      (WebPEncCSP)((int)picture->colorspace & WEBP_CSP_UV_MASK);
+  const int has_alpha = (int)picture->colorspace & WEBP_CSP_ALPHA_BIT;
   const int y_stride = width;
   const int uv_width = (width + 1) >> 1;
   const int uv_height = (height + 1) >> 1;

src/enc/vp8l.c

@@ -34,8 +34,8 @@
 // Palette reordering for smaller sum of deltas (and for smaller storage).
 
 static int PaletteCompareColorsForQsort(const void* p1, const void* p2) {
-  const uint32_t a = WebPMemToUint32(p1);
-  const uint32_t b = WebPMemToUint32(p2);
+  const uint32_t a = WebPMemToUint32((uint8_t*)p1);
+  const uint32_t b = WebPMemToUint32((uint8_t*)p2);
   assert(a != b);
   return (a < b) ? -1 : 1;
 }
@@ -224,9 +224,8 @@ static int AnalyzeEntropy(const uint32_t* argb,
     {
       double entropy_comp[kHistoTotal];
       double entropy[kNumEntropyIx];
-      EntropyIx k;
-      EntropyIx last_mode_to_analyze =
-          use_palette ? kPalette : kSpatialSubGreen;
+      int k;
+      int last_mode_to_analyze = use_palette ? kPalette : kSpatialSubGreen;
       int j;
       // Let's add one zero to the predicted histograms. The zeros are removed
       // too efficiently by the pix_diff == 0 comparison, at least one of the
@@ -263,7 +262,7 @@ static int AnalyzeEntropy(const uint32_t* argb,
       *min_entropy_ix = kDirect;
       for (k = kDirect + 1; k <= last_mode_to_analyze; ++k) {
         if (entropy[*min_entropy_ix] > entropy[k]) {
-          *min_entropy_ix = k;
+          *min_entropy_ix = (EntropyIx)k;
         }
       }
       *red_and_blue_always_zero = 1;

src/mux/muxinternal.c

@@ -16,7 +16,7 @@
 #include "./muxi.h"
 #include "../utils/utils.h"
 
-#define UNDEFINED_CHUNK_SIZE (-1)
+#define UNDEFINED_CHUNK_SIZE ((uint32_t)(-1))
 
 const ChunkInfo kChunks[] = {
   { MKFOURCC('V', 'P', '8', 'X'),  WEBP_CHUNK_VP8X,    VP8X_CHUNK_SIZE },
@@ -439,7 +439,7 @@ static int IsNotCompatible(int feature, int num_items) {
   return (feature != 0) != (num_items > 0);
 }
 
-#define NO_FLAG 0
+#define NO_FLAG ((WebPFeatureFlags)0)
 
 // Test basic constraints:
 // retrieval, maximum number of chunks by index (use -1 to skip)