I mention this only as a very dirty workaround if ST doesn't come through.
`sizeof(struct)` is determined at compile-time. So, you if include a conditional based on it, the compiler should optimize away all but one branch, and then it would optimize away the conditional entirely and simply inline the body, resulting in zero run-time overhead.
#include <stdio.h>
#include <stddef.h>
struct a {
int b[10];
};
#define LIBVER (sizeof(struct a) > 4 && offsetof(struct a,b) == 0 ? 0x55 : 0xaa)
int main(int argc, char const *argv[]) {
printf("%x\n", LIBVER);
return 0;
}
$ gcc -g -O2 -o 1 ./1.c
(gdb) disassemble main
Dump of assembler code for function main:
0x0000000000401040 <+0>: sub rsp,0x8
0x0000000000401044 <+4>: mov esi,0x55
0x0000000000401049 <+9>: mov edi,0x402010
0x000000000040104e <+14>: xor eax,eax
0x0000000000401050 <+16>: call 0x401030 <printf@plt>
0x0000000000401055 <+21>: xor eax,eax
0x0000000000401057 <+23>: add rsp,0x8
0x000000000040105b <+27>: ret
Update: extended to show use of offsetof(type,name), which may prove useful as well.
- If someone's post helped resolve your issue, please thank them by clicking "Accept as Solution".
- Please post an update with details once you've solved your issue. Your experience may help others.
