'unable to load command 0x2?' warnings under MacOS X

[Pavel Cherenkov]

Non-static binaries, compiled with gcc-mp-4.6 (from mac ports) and linked with libbfd (also from ports), at initialization point, print out warnings like: 'unable to load command 0x24' or 'unable to load command 0x26', etc.

In most cases (observed with tarantool binaries under Mac OS X Lion), the command code is >= 0x20.

The message comes from bfd/mach-o.c (as in http://opensource.apple.com/source/gdb/gdb-967/src/bfd/mach-o.c):

  switch (command->type)
    {
    case BFD_MACH_O_LC_SEGMENT:
      if (bfd_mach_o_scan_read_segment_32 (abfd, command) != 0)
 return -1;
      break;
.....
    default:
      fprintf (stderr, "unable to read unknown load command 0x%lx\n",
        (unsigned long) command->type);
      break;
    }

The warning says that BFD cannot recognize the Mach-O section load command it has encountered.

Looking at bfd/mach-o.h (http://opensource.apple.com/source/cxxfilt/cxxfilt-9/cxxfilt/bfd/mach-o.h?txt) where known load commands are described, we find that commands there range from 0x1 to 0x18, yet nothing beyond.

Mac OS X (Lion) defines load constants in /usr/include/mach-o/loader.h (available if you've installed XCode), from 0x1 to 0x27. Therefore, the most logical explanation to seeing the warnings for load codes > 0x18 appears to be the lack of the said codes in BFD's own header.

This seems to place it as a BFD-specific issue that should eventually (when the codes are brought in sync) disappear.

[Pavel Cherenkov (pcherenkov)]

The latest (non-ported) release of GNU binutils is 2.22 and it *does* include the required code:

binutils-2.22/bfd/mach-o.c:
.............
    case BFD_MACH_O_LC_DYLD_INFO:
      if (bfd_mach_o_read_dyld_info (abfd, command) != 0)
        return -1;
      break;
    case BFD_MACH_O_LC_VERSION_MIN_MACOSX:
    case BFD_MACH_O_LC_VERSION_MIN_IPHONEOS:
      if (!bfd_mach_o_read_version_min (abfd, command))
        return -1;
      break;

binutils-2.22/include/mach-o/loader.h:

  BFD_MACH_O_LC_VERSION_MIN_IPHONEOS = 0x25, /* Minimal IOS version. */
  BFD_MACH_O_LC_FUNCTION_STARTS = 0x26, /* Compressed table of func start. */
  BFD_MACH_O_LC_DYLD_ENVIRONMENT = 0x27 /* Env variable string for dyld. */

However, the latest version is not *yet* in the mac ports:
Mac-mini-tarantool ~/tmp$ port list binutils
binutils @2.21 devel/binutils
Mac-mini-tarantool ~/tmp$ port list installed | grep binutils
binutils @2.21 devel/binutils
Mac-mini-tarantool ~/tmp$ port list outdated | grep binutils
Mac-mini-tarantool ~/tmp$

[Kostja Osipov (kostja)]

Over a year without a fix, not worth bothering with.