Weak alias to static function not working

[Quuxplusone]

Bugzilla Link	PR17775
Status	NEW
Importance	P normal
Reported by	Scott Pakin (scott+llvm+bugzilla@pakin.org)
Reported on	2013-11-01 16:11:05 -0700
Last modified on	2021-04-01 07:44:10 -0700
Version	trunk
Hardware	PC Linux
CC	dgregor@apple.com, dmajor@bugmail.cc, llvm-bugs@lists.llvm.org, lukebenes@hotmail.com, scott+llvm+bugzilla@pakin.org, thierry@FreeBSD.org, tstellar@redhat.com
Fixed by commit(s)
Attachments	aliasing.cpp (200 bytes, text/x-c++src)
Blocks	PR45309
Blocked by
See also

Created attachment 11473
Minimal reproducer for weak-alias problem

Weak aliases to unused static functions fail with an error message.  It looks
like the compiler is first removing the unused static function then complaining
that it can't create a weak alias to a function that no longer exists:

$ clang++ --version | head -1
clang version 3.4 (trunk)
$ clang++ -c aliasing.cpp
aliasing.cpp:8:56: error: alias must point to a defined variable or function
  const char* do_something (void) __attribute__((weak, alias("do_somethi...
                                                       ^
1 error generated.
$ g++ --version | head -1
g++ (GCC) 4.7.2
$ g++ -c aliasing.cpp

I'm seeing this problem with r193799, but I recall it working in r190315.  This
seems to be a C++ issue; analogous C code made it through clang with no
problems.

Defining do_something_original() as non-static in the attached file makes the
problem go away, but in my real code I'd prefer to have the function declared
static.

-- Scott

[Quuxplusone]

Attached aliasing.cpp (200 bytes, text/x-c++src): Minimal reproducer for weak-alias problem

[Quuxplusone]

This is still an issue in clang 10.0.0.

[Quuxplusone]

Relevant mailing list post: http://lists.llvm.org/pipermail/cfe-dev/2018-May/057870.html

[Quuxplusone]

openhpi 3.8.0 hits this bug: https://github.com/open-hpi/openhpi/releases/tag/3.8.0