Bad symbol name in the error: undefined symbol error message

[marxin]

I noticed the following strange behavior:

namespace ns {
	void version();
};

int main()
{
  ns::version();

	return 0;
}

$ marxin@marxinbox:/tmp> g++ main.cpp -fuse-ld=mold -Wl,--version
collect2 version 13.2.1 20230912 [revision b96e66fd4ef3e36983969fb8cdd1956f551a074b]
$ g++ main.cpp -fuse-ld=mold
mold: error: undefined symbol: ns::versionv
>>> referenced by main.cpp
>>>               /tmp/ccdckvbd.o:(main)
collect2: error: ld returned 1 exit status
$ nm a-main.o
0000000000000000 T main
                 U _ZN2ns7versionEv
$ nm -C a-main.o
0000000000000000 T main
                 U ns::version()

Note the superfluous v character and compared to the usual message, the parenthesis are missing:

mold: error: undefined symbol: foo()

[rui314]

_ZN2ns7versionEv is valid as a Rust symbol of ns::versionv and C++ symbol of ns::version(). It is inherently ambiguous. Let me try to find a way to find if an object file is created by the Rust compiler.

[marxin]

That's funny!

Well, one might probably rely on:

readelf -p .comment x.o

String dump of section '.comment':
  [     1]  rustc version 1.74.0 (79e9716c9 2023-11-13)

[rui314]

Yeah, it seems like reading the contents of .comment is the best way to identify whether an object file was created by rustc or not.