Re: Problems? compiling musl toolchain

[Rich Felker <dalias@libc.org>]

On Thu, Sep 24, 2015 at 04:23:58PM +0200, Ruben Winistörfer wrote:
> First: Compiling GCC 5.2.0 (and also 4.9.3) with musl 1.1.11
> toolchain I get a lot of warnings about missing sentinels in
> function calls. Compiling GCC (same versions) with glibc toolchain
> there's no such warning at all.
> Replacing the function call sentinels 'NULL' with '(char *)NULL' in
> the affected source code of GCC makes the warnings disappear.

This warning is correct; the GCC code is wrong. NULL is not a valid
way to pass a null pointer to a variadic function, especially not in
C++ code.

> My question: Does the reason for these warnings have some impact on
> the health of the toolchain (is there something wrong?) or are they
> just a byproduct of the correctness and standards-conformance of
> musl?

musl has arranged things so that this will work ok (and won't blow up)
at runtime, but what GCC's source is doing formally incorrect and
should be fixed.

> Second: Compiling with a musl 1.1.11, GCC 5.2.0 (and 4.9.3),
> Binutils 2.25.1 toolchain I get the following info (warning) over an
> over again:
> 
> ....ld: copy reloc against protected `stdout' is dangerous
> ....ld: copy reloc against protected `stdin' is dangerous
> ....ld: copy reloc against protected `stderr' is dangerous
> 
> Same can be seen in Alpine Linux build logs: e.g. http://build.alpinelinux.org/buildlogs/build-edge-x86_64/main/patchutils/patchutils-0.3.4-r0.log
> 
> Reason for these "warnings" seems to be a change in the linker from
> binutils version 2.25 to 2.25.1.
> Lines 2677 to 2680 in 'binutils-2.25.1/bfd/elflink.c' are new and in
> my opinion the source of the issued warning.
> My C knowledge is minimal but as far as I can tell this means that
> the problem - if there is one at all - was already there before
> binutils version 2.25.1, the linker just did not print the
> "warning".
> 
> I haven't seen this warning before using glibc. So i guess it has to
> be musl-related.
> 
> What do you think? Is there a problem or can I ignore these warnings?

You can safely ignore them. I do plan to find a way to make them go
away in the next release though, since they're confusing and
concerning to many users.

Rich