http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51500
--- Comment #15 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-01-30 22:21:16 UTC --- So this should be better then: #define FFI_INIT_TRAMPOLINE_THISCALL(TRAMP,FUN,CTX,SIZE) \ { unsigned char *__tramp = (unsigned char*)(TRAMP); \ unsigned int __fun = (unsigned int)(FUN); \ unsigned int __ctx = (unsigned int)(CTX); \ unsigned int __dis = __fun - (__ctx + 22); \ *(unsigned int *) &__tramp[0] = 0x8924048b; /* mov (%esp), %eax */ \ *(unsigned int *) &__tramp[4] = 0xec83240c; /* mov %ecx, (%esp) */ \ *(unsigned int *) &__tramp[8] = 0x24048904; /* sub $4,(%esp) */ \ /* mov %eax, (%esp) */ \ *(unsigned char*) &__tramp[12] = 0xb8; \ *(unsigned int*) &__tramp[13] = __ctx; /* movl __ctx, %eax */ \ *(unsigned char *) &__tramp[17] = 0xe8; \ *(unsigned int*) &__tramp[18] = __dis; /* call __fun */ \ *(unsigned int*) &__tramp[22] = 0x83240c8b; /* mov (%esp), %ecx */ \ *(unsigned int*) &__tramp[26] = 0x0c8904c4; /* add $4, %esp */ \ *(unsigned char*) &__tramp[30] = 0x24; /* mov %ecx, (%esp) */ \ *(unsigned short*) &__tramp[31] = 0xc3; /* ret */ \ }