[freetype2] master 7227aab 68/68: Revert "[sfnt] Fix crash in `Load_SBit_Png` on Windows x64."

[Werner Lemberg]

branch: master
commit 7227aabb3e45e46cf320f56503656c39f8b63b30
Author: Werner Lemberg <wl@gnu.org>
Commit: Werner Lemberg <wl@gnu.org>

    Revert "[sfnt] Fix crash in `Load_SBit_Png` on Windows x64."
    
    This reverts commit dbf9142f7e0432c9ed618b3276e2b61fa39e7262, as discussed
    in #1037.
---
 ChangeLog          | 25 -------------------------
 src/sfnt/pngshim.c | 46 ----------------------------------------------
 2 files changed, 71 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 3c522d2..7945b1e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,28 +1,3 @@
-2021-02-27  Jesse Towner  <townerj@gmail.com>
-
-       [sfnt] Fix crash in `Load_SBit_Png` on Windows x64.
-
-       This change fixes a crash that occurs in `Load_SBit_Png` when
-       running on a 64-bit Windows OS.  A memory access violation exception
-       would be raised by `setjmp` if the `jmp_buf` is not aligned to a
-       16-byte memory boundary.  This is due to setjmp executing `movdqa`
-       instructions to store 128-bit XMM registers to memory, which require
-       correct memory alignment.  This problem occurs because
-       `png_create_read_struct` uses `malloc` and `free` for memory
-       management, which only guarantees 8-byte alignment on Windows.
-
-       Instead, to fix the problem, `png_create_read_struct_2` is used on
-       64-bit Windows, which allows for user-defined memory allocation and
-       deallocation callbacks to be specified.  These callbacks forward the
-       allocation and deallocation requests to `_aligned_alloc` and
-       `_aligned_free`, ensuring that the allocated `png_struct` and
-       internal `jmp_buf` have the requisite 16-byte alignment.
-
-       * src/sfnt/pngshim.c <_WIN64>: Include `malloc.h`.
-       (malloc_callback, free_callback) <_WIN64>: New functions.
-       (Load_SBit_Png) <_WIN64>: Use `png_create_read_struct_2` instead of
-       `png_create_read_struct`
-
 2021-02-25  Werner Lemberg  <wl@gnu.org>
 
        [woff2] Fix memory leak.
diff --git a/src/sfnt/pngshim.c b/src/sfnt/pngshim.c
index 2973b9a..c7a2938 100644
--- a/src/sfnt/pngshim.c
+++ b/src/sfnt/pngshim.c
@@ -33,16 +33,6 @@
 
 #include "sferrors.h"
 
-  /* Use _aligned_malloc / _aligned_free on 64-bit Windows to ensure that */
-  /* the jmp_buf needed for ft_setjmp is aligned to a 16-byte boundary.   */
-  /* If the jmp_buf is not aligned to a 16-byte boundary then a memory    */
-  /* access violation exception will occur upon ft_setjmp being called.   */
-#ifdef _WIN64
-#ifndef PNG_USER_MEM_SUPPORTED
-#error "libpng user-defined memory allocation is required for 64-bit Windows"
-#endif
-#include <malloc.h>
-#endif
 
   /* This code is freely based on cairo-png.c.  There's so many ways */
   /* to call libpng, and the way cairo does it is defacto standard.  */
@@ -231,32 +221,6 @@
   }
 
 
-#ifdef _WIN64
-
-  /* Memory allocation callback to ensure that the jmp_buf that is stored */
-  /* within the png_struct has 16-byte alignment for 64-bit Windows.      */
-  static png_voidp
-  malloc_callback( png_structp       png,
-                   png_alloc_size_t  size )
-  {
-    FT_UNUSED( png );
-    return _aligned_malloc( size, 16 );
-  }
-
-
-  /* Memory deallocation callback to release memory that was allocated */
-  /* with the matching memory allocation callback above.               */
-  static void
-  free_callback( png_structp  png,
-                 png_voidp    ptr )
-  {
-    FT_UNUSED( png );
-    _aligned_free( ptr );
-  }
-
-#endif /* _WIN64 */
-
-
   static void
   read_data_from_FT_Stream( png_structp  png,
                             png_bytep    data,
@@ -328,20 +292,10 @@
 
     FT_Stream_OpenMemory( &stream, data, png_len );
 
-#ifdef _WIN64
-    png = png_create_read_struct_2( PNG_LIBPNG_VER_STRING,
-                                    &error,
-                                    error_callback,
-                                    warning_callback,
-                                    NULL,
-                                    malloc_callback,
-                                    free_callback );
-#else
     png = png_create_read_struct( PNG_LIBPNG_VER_STRING,
                                   &error,
                                   error_callback,
                                   warning_callback );
-#endif
     if ( !png )
     {
       error = FT_THROW( Out_Of_Memory );