stb_image: fixes problems reported by CodeQL

Author: illwieckz

crnlib/stb_image_write.h

@@ -826,7 +826,7 @@ STBIWDEF int stbi_write_hdr(char const *filename, int x, int y, int comp, const
 static void *stbiw__sbgrowf(void **arr, int increment, int itemsize)
 {
    int m = *arr ? 2*stbiw__sbm(*arr)+increment : increment+1;
-   void *p = STBIW_REALLOC_SIZED(*arr ? stbiw__sbraw(*arr) : 0, *arr ? (stbiw__sbm(*arr)*itemsize + sizeof(int)*2) : 0, itemsize * m + sizeof(int)*2);
+   void *p = STBIW_REALLOC_SIZED(*arr ? stbiw__sbraw(*arr) : 0, *arr ? (stbiw__sbm(*arr)*itemsize + sizeof(int)*2) : 0, (size_t)itemsize * (size_t)m + sizeof(int)*2);
    STBIW_ASSERT(p);
    if (p) {
       if (!*arr) ((int *) p)[1] = 0;
@@ -1100,7 +1100,7 @@ static void stbiw__encode_png_line(unsigned char *pixels, int stride_bytes, int
    int signed_stride = stbi__flip_vertically_on_write ? -stride_bytes : stride_bytes;
 
    if (type==0) {
-      memcpy(line_buffer, z, width*n);
+      memcpy(line_buffer, z, (size_t)width * (size_t)n);
       return;
    }
 
@@ -1141,8 +1141,8 @@ STBIWDEF unsigned char *stbi_write_png_to_mem(const unsigned char *pixels, int s
       force_filter = -1;
    }
 
-   filt = (unsigned char *) STBIW_MALLOC((x*n+1) * y); if (!filt) return 0;
-   line_buffer = (signed char *) STBIW_MALLOC(x * n); if (!line_buffer) { STBIW_FREE(filt); return 0; }
+   filt = (unsigned char *) STBIW_MALLOC(((size_t)x * (size_t)n+1) * (size_t)y); if (!filt) return 0;
+   line_buffer = (signed char *) STBIW_MALLOC((size_t)x * (size_t)n); if (!line_buffer) { STBIW_FREE(filt); return 0; }
    for (j=0; j < y; ++j) {
       int filter_type;
       if (force_filter > -1) {
@@ -1169,8 +1169,8 @@ STBIWDEF unsigned char *stbi_write_png_to_mem(const unsigned char *pixels, int s
          }
       }
       // when we get here, filter_type contains the filter type, and line_buffer contains the data
-      filt[j*(x*n+1)] = (unsigned char) filter_type;
-      STBIW_MEMMOVE(filt+j*(x*n+1)+1, line_buffer, x*n);
+      filt[(size_t)j * ((size_t)x * (size_t)n + 1)] = (unsigned char) filter_type;
+      STBIW_MEMMOVE(filt + (size_t)j * ((size_t)x * (size_t)n + 1) + 1, line_buffer, (size_t)x * (size_t)n);
    }
    STBIW_FREE(line_buffer);
    zlib = stbi_zlib_compress(filt, y*( x*n+1), &zlen, stbi_write_png_compression_level);