more C89-fixes

going down to strict -ansi c89 is quite overkill (no 'inline',
and /* */-style comments).
But with these fixes, the code compiles with the stringent flags:
 -Wextra -Wold-style-definition -Wmissing-prototypes
 -Wmissing-declarations and -Wdeclaration-after-statement

Change-Id: I36222f8f505bcba3d9d1309ad98b5ccb04ec17e3

src/enc/Makefile.in

@@ -266,7 +266,7 @@ clean-noinstLTLIBRARIES:
 	  echo "rm -f \"$${dir}/so_locations\""; \
 	  rm -f "$${dir}/so_locations"; \
 	done
-libwebpencode.la: $(libwebpencode_la_OBJECTS) $(libwebpencode_la_DEPENDENCIES) 
+libwebpencode.la: $(libwebpencode_la_OBJECTS) $(libwebpencode_la_DEPENDENCIES)
 	$(libwebpencode_la_LINK)  $(libwebpencode_la_OBJECTS) $(libwebpencode_la_LIBADD) $(LIBS)
 
 mostlyclean-compile:

src/enc/dsp.c

@@ -21,9 +21,11 @@ extern "C" {
 
 static uint8_t clip1[255 + 510 + 1];    // clips [-255,510] to [0,255]
 
-static int tables_ok = 0;
+// We declare this variable 'volatile' to prevent instruction reordering
+// and make sure it's set to true _last_ (so as to be thread-safe)
+static volatile int tables_ok = 0;
 
-static void InitTables() {
+static void InitTables(void) {
   if (!tables_ok) {
     int i;
     for (i = -255; i <= 255 + 255; ++i) {
@@ -79,7 +81,7 @@ static void ITransform(const uint8_t* ref, const int16_t* in, uint8_t* dst) {
   }
 }
 
-void FTransform(const uint8_t* src, const uint8_t* ref, int16_t* out) {
+static void FTransform(const uint8_t* src, const uint8_t* ref, int16_t* out) {
   int i;
   int tmp[16];
   for (i = 0; i < 4; ++i, src += BPS, ref += BPS) {
@@ -636,7 +638,7 @@ VP8BlockCopy VP8Copy16x16 = Copy16x16;
 
 //-----------------------------------------------------------------------------
 
-void VP8EncDspInit() {
+void VP8EncDspInit(void) {
   InitTables();
 }
 

src/enc/filter.c

@@ -25,7 +25,7 @@ static uint8_t clip1[255 + 510 + 1];    // clips [-255,510] to [0,255]
 
 static int tables_ok = 0;
 
-static void InitTables() {
+static void InitTables(void) {
   if (!tables_ok) {
     int i;
     for (i = -255; i <= 255; ++i) {

src/enc/iterator.c

@@ -270,7 +270,7 @@ int VP8IteratorNext(VP8EncIterator* const it,
 //-----------------------------------------------------------------------------
 // Helper function to set mode properties
 
-void VP8SetIntra16Mode(const VP8EncIterator* it, int mode) {
+void VP8SetIntra16Mode(const VP8EncIterator* const it, int mode) {
   int y;
   uint8_t* preds = it->preds_;
   for (y = 0; y < 4; ++y) {

src/enc/picture.c

@@ -38,7 +38,7 @@ int WebPPictureAlloc(WebPPicture* const picture) {
     picture->y_stride = width;
     picture->uv_stride = uv_width;
     WebPPictureFree(picture);   // erase previous buffer
-    picture->y = (uint8_t*)malloc(total_size);
+    picture->y = (uint8_t*)malloc((size_t)total_size);
     if (picture->y == NULL) return 0;
     picture->u = picture->y + y_size;
     picture->v = picture->u + uv_size;
@@ -163,7 +163,7 @@ enum { YUV_FRAC = 16 };
 
 static inline int clip_uv(int v) {
    v = (v + (257 << (YUV_FRAC + 2 - 1))) >> (YUV_FRAC + 2);
-   return ((v & ~0xff) == 0) ? v : (v < 0) ? 0u : 255u;
+   return ((v & ~0xff) == 0) ? v : (v < 0) ? 0 : 255;
 }
 
 static inline int rgb_to_y(int r, int g, int b) {

src/enc/vp8enci.h

@@ -455,7 +455,7 @@ typedef enum {
 typedef int (*VP8CPUInfo)(CPUFeature feature);
 extern VP8CPUInfo CPUInfo;
 
-void VP8EncDspInit();   // must be called before using anything from the above.
+void VP8EncDspInit(void);   // must be called before using any of the above
 
   // in filter.c
 extern void VP8InitFilter(VP8EncIterator* const it);

src/enc/webpenc.c

@@ -29,7 +29,7 @@ extern "C" {
 
 //-----------------------------------------------------------------------------
 
-int WebPGetEncoderVersion() {
+int WebPGetEncoderVersion(void) {
   return (ENC_MAJ_VERSION << 16) | (ENC_MIN_VERSION << 8) | ENC_REV_VERSION;
 }
 
@@ -39,6 +39,10 @@ int WebPGetEncoderVersion() {
 
 static int DummyWriter(const uint8_t* data, size_t data_size,
                        const WebPPicture* const picture) {
+  // The following are to prevent 'unused variable' error message.
+  (void)data;
+  (void)data_size;
+  (void)picture;
   return 1;
 }