pixman-glyph.c: Add __force_align_arg_pointer to composite functions

The functions pixman_composite_glyphs_no_mask() and
pixman_composite_glyphs() can call into code compiled with -msse2,
which requires the stack to be aligned to 16 bytes. Since the ABIs on
Windows and Linux for x86-32 don't provide this guarantee, we need to
use this attribute to make GCC generate a prologue that realigns the
stack.

This fixes the crash introduced in the previous commit and also

   https://bugs.freedesktop.org/show_bug.cgi?id=70348

and

   https://bugs.freedesktop.org/show_bug.cgi?id=68300

diff --git a/pixman/pixman-glyph.c b/pixman/pixman-glyph.c
index 5a271b64b897513321f5bc54245f285e54219340..96a349ab472720b4eb27299ba143c8fa9162def0 100644 (file)
--- a/pixman/pixman-glyph.c
+++ b/pixman/pixman-glyph.c
@@ -391,6 +391,9 @@ box32_intersect (pixman_box32_t *dest,
     return dest->x2 > dest->x1 && dest->y2 > dest->y1;
 }
 
+#if defined(__GNUC__) && !defined(__x86_64__) && !defined(__amd64__)
+__attribute__((__force_align_arg_pointer__))
+#endif
 PIXMAN_EXPORT void
 pixman_composite_glyphs_no_mask (pixman_op_t            op,
                                 pixman_image_t        *src,
@@ -630,6 +633,9 @@ out:
  *   - Trim the mask to the destination clip/image?
  *   - Trim composite region based on sources, when the op ignores 0s.
  */
+#if defined(__GNUC__) && !defined(__x86_64__) && !defined(__amd64__)
+__attribute__((__force_align_arg_pointer__))
+#endif
 PIXMAN_EXPORT void
 pixman_composite_glyphs (pixman_op_t            op,
                         pixman_image_t        *src,