Avoid mixing incompatible CRTs when linking to libpng.dll

If libpng.dll is built using static linking (without importing C runtimes from whatever version of ms compiler that was used to build it), or when it was build by mingw then such dll won't work properly as stdio fread/fwrite will try to interpret FILE pointers from unrelated CRT and will result in undefined behavior.

png.c

@@ -699,6 +699,9 @@ png_get_io_ptr(png_const_structrp png_ptr)
  * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a
  * function of your own because "FILE *" isn't necessarily available.
  */
+#ifdef png_init_io
+#undef png_init_io
+#endif
 void PNGAPI
 png_init_io(png_structrp png_ptr, png_FILE_p fp)
 {
@@ -711,6 +714,36 @@ png_init_io(png_structrp png_ptr, png_FILE_p fp)
 }
 #  endif
 
+void PNGAPI
+png_init_io2(png_structrp png_ptr, png_FILE_p fp, png_fread_ptr fread_fn,
+   png_fwrite_ptr fwrite_fn, png_fflush_ptr fflush_fn)
+{
+   if (png_ptr->read_data_fn != NULL)
+   {
+      png_init_read_io(png_ptr, fp, fread_fn);
+   }
+   else
+   {
+      png_init_write_io(png_ptr, fp, fwrite_fn, fflush_fn);
+   }
+}
+
+void PNGAPI
+png_init_read_io(png_structrp png_ptr, png_FILE_p fp, png_fread_ptr fread_fn)
+{
+   png_debug(1, "in png_init_read_io");
+   png_set_read_fn2(png_ptr, fp, png_default_read_data, fread_fn);
+}
+
+void PNGAPI
+png_init_write_io(png_structrp png_ptr, png_FILE_p fp, png_fwrite_ptr fwrite_fn,
+   png_fflush_ptr fflush_fn)
+{
+   png_debug(1, "in png_init_write_io");
+   png_set_write_fn2(png_ptr, fp, png_default_write_data, png_default_flush,
+      fwrite_fn, fflush_fn);
+}
+
 #  ifdef PNG_SAVE_INT_32_SUPPORTED
 /* PNG signed integers are saved in 32-bit 2's complement format.  ANSI C-90
  * defines a cast of a signed integer to an unsigned integer either to preserve

png.h

@@ -811,6 +811,12 @@ typedef PNG_CALLBACK(void, *png_read_status_ptr, (png_structp, png_uint_32,
 typedef PNG_CALLBACK(void, *png_write_status_ptr, (png_structp, png_uint_32,
     int));
 
+typedef PNG_CALLBACK(size_t, *png_fread_ptr, (png_voidp, png_size_t,
+   png_size_t, png_FILE_p));
+typedef PNG_CALLBACK(size_t, *png_fwrite_ptr, (png_const_voidp, png_size_t,
+   png_size_t, png_FILE_p));
+typedef PNG_CALLBACK(int, *png_fflush_ptr, (png_FILE_p));
+
 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
 typedef PNG_CALLBACK(void, *png_progressive_info_ptr, (png_structp, png_infop));
 typedef PNG_CALLBACK(void, *png_progressive_end_ptr, (png_structp, png_infop));
@@ -1589,6 +1595,29 @@ PNG_EXPORT(226, void, png_set_text_compression_method, (png_structrp png_ptr,
 #ifdef PNG_STDIO_SUPPORTED
 /* Initialize the input/output for the PNG file to the default functions. */
 PNG_EXPORT(74, void, png_init_io, (png_structrp png_ptr, png_FILE_p fp));
+PNG_EXPORT(250, void, png_init_io2, (png_structrp png_ptr, png_FILE_p fp,
+   png_fread_ptr fread_fn, png_fwrite_ptr fwrite_fn,
+   png_fflush_ptr fflush_fn));
+
+static inline png_size_t
+png_fread_(png_voidp buf, png_size_t sz, png_size_t count, png_FILE_p fp)
+{
+   return fread(buf, sz, count, fp);
+}
+
+static inline png_size_t
+png_fwrite_(png_const_voidp buf, png_size_t sz, png_size_t count, png_FILE_p fp)
+{
+   return fwrite(buf, sz, count, fp);
+}
+
+static inline int png_fflush_(png_FILE_p fp)
+{
+   return fflush(fp);
+}
+
+#define png_init_io(png_ptr, fp) png_init_io2((png_ptr), (fp), png_fread_, \
+   png_fwrite_, png_fflush_)
 #endif
 
 /* Replace the (error and abort), and warning functions with user
@@ -1618,10 +1647,18 @@ PNG_EXPORT(76, png_voidp, png_get_error_ptr, (png_const_structrp png_ptr));
 PNG_EXPORT(77, void, png_set_write_fn, (png_structrp png_ptr, png_voidp io_ptr,
     png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn));
 
+/* Initialize the output for the PNG file. */
+PNG_EXPORT(251, void, png_init_write_io, (png_structrp png_ptr, png_FILE_p fp,
+   png_fwrite_ptr fwrite_fn, png_fflush_ptr fflush_fn));
+
 /* Replace the default data input function with a user supplied one. */
 PNG_EXPORT(78, void, png_set_read_fn, (png_structrp png_ptr, png_voidp io_ptr,
     png_rw_ptr read_data_fn));
 
+/* Initialize the input for the PNG file. */
+PNG_EXPORT(252, void, png_init_read_io, (png_structrp png_ptr, png_FILE_p fp,
+   png_fread_ptr fread_fn));
+
 /* Return the user pointer associated with the I/O functions */
 PNG_EXPORT(79, png_voidp, png_get_io_ptr, (png_const_structrp png_ptr));
 
@@ -3266,7 +3303,7 @@ PNG_EXPORT(244, int, png_set_option, (png_structrp png_ptr, int option,
  * one to use is one more than this.)
  */
 #ifdef PNG_EXPORT_LAST_ORDINAL
-  PNG_EXPORT_LAST_ORDINAL(249);
+  PNG_EXPORT_LAST_ORDINAL(252);
 #endif
 
 #ifdef __cplusplus

pngpriv.h

@@ -1054,6 +1054,14 @@ PNG_INTERNAL_FUNCTION(void,png_zfree,(voidpf png_ptr, voidpf ptr),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_default_read_data,(png_structp png_ptr,
     png_bytep data, png_size_t length),PNG_EMPTY);
 
+PNG_INTERNAL_FUNCTION(void PNGCBAPI, png_set_read_fn2, (png_structrp png_ptr,
+   png_voidp io_ptr, png_rw_ptr read_data_fn, png_fread_ptr fread_fn),
+   PNG_EMPTY);
+
+PNG_INTERNAL_FUNCTION(void PNGCBAPI, png_set_write_fn2, (png_structrp png_ptr,
+   png_voidp io_ptr, png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn,
+   png_fwrite_ptr fwrite_fn, png_fflush_ptr fflush_fn), PNG_EMPTY);
+
 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
 PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_push_fill_buffer,(png_structp png_ptr,
     png_bytep buffer, png_size_t length),PNG_EMPTY);

pngrio.c

@@ -40,7 +40,6 @@ png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length)
       png_error(png_ptr, "Call to NULL read function");
 }
 
-#ifdef PNG_STDIO_SUPPORTED
 /* This is the function that does the actual reading of data.  If you are
  * not reading from a standard C stream, you should create a replacement
  * read_data function and use it at run time with png_set_read_fn(), rather
@@ -51,18 +50,47 @@ png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
 {
    png_size_t check;
 
-   if (png_ptr == NULL)
+   if (png_ptr == NULL || png_ptr->fread_fn == NULL)
       return;
 
    /* fread() returns 0 on error, so it is OK to store this in a png_size_t
     * instead of an int, which is what fread() actually returns.
     */
-   check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr));
+   check = png_ptr->fread_fn(data, 1, length, png_voidcast(png_FILE_p,
+       png_ptr->io_ptr));
 
    if (check != length)
       png_error(png_ptr, "Read Error");
 }
+
+void /* PRIVATE */
+png_set_read_fn2(png_structrp png_ptr, png_voidp io_ptr,
+   png_rw_ptr read_data_fn, png_fread_ptr fread_fn)
+{
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->io_ptr = io_ptr;
+   png_ptr->read_data_fn = read_data_fn;
+   png_ptr->fread_fn = fread_fn;
+
+#ifdef PNG_WRITE_SUPPORTED
+   /* It is an error to write to a read device */
+   if (png_ptr->write_data_fn != NULL)
+   {
+      png_ptr->write_data_fn = NULL;
+      png_ptr->fwrite_fn = NULL;
+      png_warning(png_ptr,
+         "Can't set both read_data_fn and write_data_fn in the"
+         " same structure");
+   }
+#endif
+
+#ifdef PNG_WRITE_FLUSH_SUPPORTED
+   png_ptr->output_flush_fn = NULL;
+   png_ptr->fflush_fn = NULL;
 #endif
+}
 
 /* This function allows the application to supply a new input function
  * for libpng if standard C streams aren't being used.
@@ -87,34 +115,14 @@ void PNGAPI
 png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
     png_rw_ptr read_data_fn)
 {
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->io_ptr = io_ptr;
-
+   png_fread_ptr fread_fn = NULL;
 #ifdef PNG_STDIO_SUPPORTED
-   if (read_data_fn != NULL)
-      png_ptr->read_data_fn = read_data_fn;
-
-   else
-      png_ptr->read_data_fn = png_default_read_data;
-#else
-   png_ptr->read_data_fn = read_data_fn;
-#endif
-
-#ifdef PNG_WRITE_SUPPORTED
-   /* It is an error to write to a read device */
-   if (png_ptr->write_data_fn != NULL)
+   if (read_data_fn == NULL)
    {
-      png_ptr->write_data_fn = NULL;
-      png_warning(png_ptr,
-          "Can't set both read_data_fn and write_data_fn in the"
-          " same structure");
+      read_data_fn = png_default_read_data;
+      fread_fn = png_fread_;
    }
 #endif
-
-#ifdef PNG_WRITE_FLUSH_SUPPORTED
-   png_ptr->output_flush_fn = NULL;
-#endif
+   png_set_read_fn2(png_ptr, io_ptr, read_data_fn, fread_fn);
 }
 #endif /* READ */

pngstruct.h

@@ -478,6 +478,12 @@ struct png_struct_def
 #if defined(PNG_COLORSPACE_SUPPORTED) || defined(PNG_GAMMA_SUPPORTED)
    png_colorspace   colorspace;
 #endif
+#endif
+
+   png_fread_ptr fread_fn;  /* function for reading input data */
+   png_fwrite_ptr fwrite_fn;   /* function for writing output data */
+#ifdef PNG_WRITE_FLUSH_SUPPORTED
+   png_fflush_ptr fflush_fn; /* Function for flushing output */
 #endif
 };
 #endif /* PNGSTRUCT_H */

pngwio.c

@@ -52,10 +52,10 @@ png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
 {
    png_size_t check;
 
-   if (png_ptr == NULL)
+   if (png_ptr == NULL || png_ptr->fwrite_fn == NULL)
       return;
 
-   check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
+   check = png_ptr->fwrite_fn(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
 
    if (check != length)
       png_error(png_ptr, "Write Error");
@@ -74,21 +74,54 @@ png_flush(png_structrp png_ptr)
       (*(png_ptr->output_flush_fn))(png_ptr);
 }
 
-#  ifdef PNG_STDIO_SUPPORTED
 void PNGCBAPI
 png_default_flush(png_structp png_ptr)
 {
    png_FILE_p io_ptr;
 
-   if (png_ptr == NULL)
+   if (png_ptr == NULL || png_ptr->fflush_fn == NULL)
       return;
 
    io_ptr = png_voidcast(png_FILE_p, (png_ptr->io_ptr));
-   fflush(io_ptr);
+   png_ptr->fflush_fn(io_ptr);
 }
-#  endif
 #endif
 
+void /* PRIVATE */
+png_set_write_fn2(png_structrp png_ptr, png_voidp io_ptr,
+   png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn,
+   png_fwrite_ptr fwrite_fn, png_fflush_ptr fflush_fn)
+{
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->io_ptr = io_ptr;
+
+   png_ptr->write_data_fn = write_data_fn;
+   png_ptr->fwrite_fn = fwrite_fn;
+
+#ifdef PNG_WRITE_FLUSH_SUPPORTED
+   png_ptr->output_flush_fn = output_flush_fn;
+   png_ptr->fflush_fn = fflush_fn;
+#else
+   PNG_UNUSED(output_flush_fn)
+   PNG_UNUSED(fflush_fn)
+#endif /* WRITE_FLUSH */
+
+#ifdef PNG_READ_SUPPORTED
+   /* It is an error to read while writing a png file */
+   if (png_ptr->read_data_fn != NULL)
+   {
+      png_ptr->read_data_fn = NULL;
+      png_ptr->fread_fn = NULL;
+
+      png_warning(png_ptr,
+          "Can't set both read_data_fn and write_data_fn in the"
+          " same structure");
+   }
+#endif
+}
+
 /* This function allows the application to supply new output functions for
  * libpng if standard C streams aren't being used.
  *
@@ -122,47 +155,24 @@ void PNGAPI
 png_set_write_fn(png_structrp png_ptr, png_voidp io_ptr,
     png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 {
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->io_ptr = io_ptr;
-
+   png_fwrite_ptr fwrite_fn = NULL;
+   png_fflush_ptr fflush_fn = NULL;
 #ifdef PNG_STDIO_SUPPORTED
-   if (write_data_fn != NULL)
-      png_ptr->write_data_fn = write_data_fn;
-
-   else
-      png_ptr->write_data_fn = png_default_write_data;
-#else
-   png_ptr->write_data_fn = write_data_fn;
+   if (write_data_fn == NULL)
+   {
+      write_data_fn = png_default_write_data;
+      fwrite_fn = png_fwrite_;
+   }
 #endif
 
-#ifdef PNG_WRITE_FLUSH_SUPPORTED
-#  ifdef PNG_STDIO_SUPPORTED
-
-   if (output_flush_fn != NULL)
-      png_ptr->output_flush_fn = output_flush_fn;
-
-   else
-      png_ptr->output_flush_fn = png_default_flush;
-
-#  else
-   png_ptr->output_flush_fn = output_flush_fn;
-#  endif
-#else
-   PNG_UNUSED(output_flush_fn)
-#endif /* WRITE_FLUSH */
-
-#ifdef PNG_READ_SUPPORTED
-   /* It is an error to read while writing a png file */
-   if (png_ptr->read_data_fn != NULL)
+#if defined(PNG_WRITE_FLUSH_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
+   if (output_flush_fn == NULL)
    {
-      png_ptr->read_data_fn = NULL;
-
-      png_warning(png_ptr,
-          "Can't set both read_data_fn and write_data_fn in the"
-          " same structure");
+      output_flush_fn = png_default_flush;
+      fflush_fn = png_fflush_;
    }
 #endif
+   png_set_write_fn2(png_ptr, io_ptr, write_data_fn, output_flush_fn,
+      fwrite_fn, fflush_fn);
 }
 #endif /* WRITE */

scripts/symbols.def

@@ -254,3 +254,6 @@ EXPORTS
  png_set_eXIf @247
  png_get_eXIf_1 @248
  png_set_eXIf_1 @249
+ png_init_io2 @250
+ png_init_write_io @251
+ png_init_read_io @252