Re: clang -pg, libm and the _end symbol

[Raphael Kubo da Costa]

Konstantin Belousov <kostik...@gmail.com> writes:

> On Wed, Feb 24, 2016 at 01:54:25PM +0100, Dimitry Andric wrote:
>> On 24 Feb 2016, at 12:27, Raphael Kubo da Costa <rak...@freebsd.org> wrote:
>> > 
>> > I'm reviewing an update to the textproc/miller port in bug 207194, and
>> > noticed it does some ugly things in post-configure to seemingly
>> > work around the following problem (on 11-HEAD at least):
>> > 
>> > % echo 'int main(void) { return 0; }' > foo.c
>> > % clang -pg foo.c -lm
>> > /usr/bin/ld: undefined reference to symbol `_end' (try adding -lc)
>> > //lib/libc.so.7: could not read symbols: Bad value
>> > cc: error: linker command failed with exit code 1 (use -v to see
>> > invocation)
>> 
>> Try using: clang -pg foo.c -lm_p
>> 
>> That works for me (also with gcc).
>
> It probably not quite works, in the sense that it resolves _end to
> something not correctly provided by libm_p.a.  In other words, sbrk(),
> if used for anything, would be broken.

It at least "works" in the sense that clang doesn't fail; however, in
addition to kib's point this doesn't look optimal from a ports
perspective, as it requires giving special treatment to certain targets
and possibly hacking the build system in different ports.

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clang -pg, libm and the _end symbol

[Raphael Kubo da Costa]

I'm reviewing an update to the textproc/miller port in bug 207194, and
noticed it does some ugly things in post-configure to seemingly
work around the following problem (on 11-HEAD at least):

 % echo 'int main(void) { return 0; }' > foo.c
 % clang -pg foo.c -lm
 /usr/bin/ld: undefined reference to symbol `_end' (try adding -lc)
 //lib/libc.so.7: could not read symbols: Bad value
 cc: error: linker command failed with exit code 1 (use -v to see
 invocation)

(FWIW, using another library such as -lz instead of -lm retuls in the
same problem)

Adding LDFLAGS+=-lc to the port's Makefile would've been enough, but I'm
not sure if it'd be just working around an actual bug, plus libtool
automatically strips -lc from the linker invocation:

 7534   *-*-openbsd* | *-*-freebsd* | *-*-dragonfly* | *-*-bitrig*)
 7535 # Do not include libc due to us having libc/libc_r.
 7536 test X-lc = "X$arg" && continue

The port builds and links fine on 9.3 without any workarounds, and if I
explicitly use ld.gold to link the above file it also works on HEAD.

Is clang working as expected or is this a bug?

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