Investigate -pie vs -Wl,-pie on OS X

[from a blog comment]

I believe for Mac OS X you need to use -Wl,-pie even with gcc. If you use gcc -v when linking on Mac OS X you won't see -pie being passed to the linker. Here's the output of otool -h on an executable built with -pie in LDFLAGS on Mac OS X 10.6:

Mach header
magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
0xfeedfacf 16777223 3 0x80 2 11 1776 0x00000085

Compare that to one built with -Wl,-pie

Mach header
magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
0xfeedfacf 16777223 3 0x80 2 11 1776 0x00200085

In /usr/include/mach-o/loader.h we find this:

#define MH_PIE 0x200000 /* When this bit is set, the OS will
load the main executable at a
random address. Only used in
MH_EXECUTE filetypes. */