[libc] add stdlib.h header to the _Exit func proxy in full build

[ghost]

No description provided.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Job Henandez Lara (Jobhdez)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/114718.diff

1 Files Affected:

• (modified) libc/hdr/func/_Exit.h (+2-1)

diff --git a/libc/hdr/func/_Exit.h b/libc/hdr/func/_Exit.h
index 575b0426e508c6..e024a651a50bcf 100644
--- a/libc/hdr/func/_Exit.h
+++ b/libc/hdr/func/_Exit.h
@@ -10,7 +10,8 @@
 #define LLVM_LIBC_HDR_FUNC_EXIT_H
 
 #ifdef LIBC_FULL_BUILD
-extern "C" void _Exit(int);
+// We will use the `_Exit` declaration from our generated stdlib.h
+#include <stdlib.h>
 
 #else // Overlay mode
 

[nickdesaulniers]

Do you have more info about this change? Why not just provide the declaration here?

[ghost]

Do you have more info about this change? Why not just provide the declaration here?

the previous declaration was conflicted with the one generated in our stdlib.h:

/home/llvm-libc-buildbot/buildbot-worker/libc-x86_64-debian-fullbuild/libc-x86_64-debian-gcc-fullbuild-dbg/build/projects/libc/include/stdlib.h:101:16: error: function ‘void _Exit(int)’ declared ‘[[noreturn]]’ but its first declaration was not
  101 | _Noreturn void _Exit(int) __NOEXCEPT;

Should we remove __NOEXCEPT in our _Exit, because it is annotated as THROW in glibc header?

[nickdesaulniers]

Should we remove __NOEXCEPT in our _Exit

I would expect exit to be noecept, since exit may execute callbacks provided by the user via atexit or on_exit calls. If those callbacks throw when invoked via a call to exit, then it will appear that the call to exit threw. But _Exit is supposed to skip those callbacks.

So it's not clear to my why glibc does not mark it's _Exit as noexcept.

[nickdesaulniers]

extern void _Exit (int __status) __THROW __attribute__ ((__noreturn__));

is what my glibc host's headers have. __THROW which expands to:

#  define __THROW       __attribute__ ((__nothrow__ __LEAF))

so glibc's _Exit is nothrow.

---

regardless, the warning is about noreturn, not nothrow. The question isn't about throw/nothrow, it's that our declaration was missing noreturn. If we redeclare a function, it needs to keep noreturn once declared with that fn attr.

[ghost]

extern void _Exit (int __status) __THROW __attribute__ ((__noreturn__));

is what my glibc host's headers have. __THROW which expands to:

#  define __THROW       __attribute__ ((__nothrow__ __LEAF))

so glibc's _Exit is nothrow.

regardless, the warning is about noreturn, not nothrow. The question isn't about throw/nothrow, it's that our declaration was missing noreturn. If we redeclare a function, it needs to keep noreturn once declared with that fn attr.

So do you want me to do a quick pr and add this to the proxy

[[noreturn]] void _Exit() noexcept;

Can you please confirm if this declaration is the right one. Thanks

[nickdesaulniers]

So do you want me to do a quick pr and add this to the proxy

[[noreturn]] void _Exit() noexcept;

Can you please confirm if this declaration is the right one. Thanks

don't forget the int parameter!

[[noreturn]] void _Exit(int) noexcept;

but yeah, I'd approve such a PR.

[ghost]

So do you want me to do a quick pr and add this to the proxy
[[noreturn]] void _Exit() noexcept;
Can you please confirm if this declaration is the right one. Thanks

don't forget the int parameter!

[[noreturn]] void _Exit(int) noexcept;

but yeah, I'd approve such a PR.

Ok will do this now