edit: Thanks, I just checked and the warning doesn't work https://godbolt.org/z/4TP1hfx4j https://godbolt.org/z/4TP1hfx4j But your hint found -fno-delete-null

edit: Thanks, I just checked and the warning doesn't work https://godbolt.org/z/4TP1hfx4j https://godbolt.org/z/4TP1hfx4j But your hint found -fno-delete-null-pointer-checks which does the trick https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html And -fno-delete-null-pointer-checks made it into LLVM too. It's a good to know but a little late for when I needed it, cheers :) % cc -O3 -fno-delete-null-pointer-checks -Wall -Wextra -c foo.c % objdump -dr foo.o foo.o: file format Mach-O 64-bit x86-64 Disassembly of section __TEXT,__text: 0000000000000000 _foo: 0: 55 pushq %rbp 1: 48 89 e5 movq %rsp, %rbp 4: 48 85 ff testq %rdi, %rdi 7: 74 04 je 4 <_foo+0xd> 9: 8b 07 movl (%rdi), %eax b: 5d popq %rbp c: c3 retq d: bf 02 00 00 00 movl $2, %edi 12: e8 00 00 00 00 callq 0 <_foo+0x17> 0000000000000013: X86_64_RELOC_BRANCH _exit