libbacktrace patch committed: Correctly swap Mach-O fat 32-bit file offset

[Ian Lance Taylor via Gcc-patches]

This libbacktrace patch correctly swaps the 32-bit file offset in a
Mach-O fat file.  This is based on a patch by Francois-Xavier Coudert
, who analyzed the problem.  This is for PR 96973.  Bootstrapped and
ran libbacktrace tests on x86_64-pc-linux-gnu.  Committed to mainline.

Ian

        PR libbacktrace/96973
         * macho.c (macho_add_fat): Correctly swap 32-bit file offset.

diff --git a/libbacktrace/macho.c b/libbacktrace/macho.c
index bd737226ca6..20dd3262d58 100644
--- a/libbacktrace/macho.c
+++ b/libbacktrace/macho.c
@@ -793,13 +793,24 @@ macho_add_fat (struct backtrace_state *state, const char 
*filename,
 
   for (i = 0; i < nfat_arch; ++i)
     {
-      struct macho_fat_arch_64 fat_arch;
       uint32_t fcputype;
+      uint64_t foffset;
 
       if (is_64)
-       memcpy (&fat_arch,
-               (const char *) arch_view.data + i * arch_size,
-               arch_size);
+       {
+         struct macho_fat_arch_64 fat_arch_64;
+
+         memcpy (&fat_arch_64,
+                 (const char *) arch_view.data + i * arch_size,
+                 arch_size);
+         fcputype = fat_arch_64.cputype;
+         foffset = fat_arch_64.offset;
+         if (swapped)
+           {
+             fcputype = __builtin_bswap32 (fcputype);
+             foffset = __builtin_bswap64 (foffset);
+           }
+       }
       else
        {
          struct macho_fat_arch fat_arch_32;
@@ -807,26 +818,18 @@ macho_add_fat (struct backtrace_state *state, const char 
*filename,
          memcpy (&fat_arch_32,
                  (const char *) arch_view.data + i * arch_size,
                  arch_size);
-         fat_arch.cputype = fat_arch_32.cputype;
-         fat_arch.cpusubtype = fat_arch_32.cpusubtype;
-         fat_arch.offset = (uint64_t) fat_arch_32.offset;
-         fat_arch.size = (uint64_t) fat_arch_32.size;
-         fat_arch.align = fat_arch_32.align;
-         fat_arch.reserved = 0;
+         fcputype = fat_arch_32.cputype;
+         foffset = (uint64_t) fat_arch_32.offset;
+         if (swapped)
+           {
+             fcputype = __builtin_bswap32 (fcputype);
+             foffset = (uint64_t) __builtin_bswap32 ((uint32_t) foffset);
+           }
        }
 
-      fcputype = fat_arch.cputype;
-      if (swapped)
-       fcputype = __builtin_bswap32 (fcputype);
-
       if (fcputype == cputype)
        {
-         uint64_t foffset;
-
          /* FIXME: What about cpusubtype?  */
-         foffset = fat_arch.offset;
-         if (swapped)
-           foffset = __builtin_bswap64 (foffset);
          backtrace_release_view (state, &arch_view, error_callback, data);
          return macho_add (state, filename, descriptor, foffset, match_uuid,
                            base_address, skip_symtab, error_callback, data,