Hi,

I think that Clang erroneously discards a function annotated with __attribute__((constructor)) when flags -Os -fno-common are given. Test case below.

What do you think?

Thanks.

----8<--------8<--------8<--------8<--------8<--------8<-------- $ cat ctor.c int val;

static void __attribute__((constructor)) init_fn(void) { val = 1; }

int main(int argc, char *argv[]) { return val; } ----8<--------8<--------8<--------8<--------8<--------8<--------

Here is what I observed:

- Clang (10.0.0-4ubuntu1) with -Os -fno-common: function init_fn() is NOT emitted, - Clang (10.0.0-4ubuntu1) with no flag, or only -Os or -fno-common: init_fn() is present as expected, - GCC (Ubuntu 9.3.0-10ubuntu1) with the same flags: init_fn() is present too, - Since https://reviews.llvm.org/D75056, -fno-common is the default and therefore -Os is enough to cause the issue.

----8<--------8<--------8<--------8<--------8<--------8<-------- $ clang --target=arm-linux-gnueabihf -Os -fno-common -S ctor.c \ -o /dev/stdout | grep init_fn $ clang --target=arm-linux-gnueabihf -Os -S ctor.c \ -o /dev/stdout | grep init_fn .p2align 2 @ -- Begin function init_fn .type init_fn,%function .code 32 @ @init_fn init_fn: .size init_fn, .Lfunc_end0-init_fn .long init_fn(target1) .addrsig_sym init_fn $ clang --target=arm-linux-gnueabihf -fno-common -S ctor.c \ -o /dev/stdout | grep init_fn .p2align 2 @ -- Begin function init_fn .type init_fn,%function .code 32 @ @init_fn init_fn: .size init_fn, .Lfunc_end0-init_fn .long init_fn(target1) .addrsig_sym init_fn $ arm-linux-gnueabihf-gcc -Os -fno-common -S ctor.c \ -o /dev/stdout | grep init_fn .type init_fn, %function init_fn: .size init_fn, .-init_fn .word init_fn(target1) ----8<--------8<--------8<--------8<--------8<--------8<--------