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Date: Tue, 12 Mar 2019 20:43:05 -0400
From: Rich Felker <>
Subject: Re: Warnings to be ignored when building musl

On Mon, Mar 11, 2019 at 01:16:39PM +0200, Dmitry Golovin wrote:
> I'm building musl 1.1.21 with clang and I get a lot of compiler
> warnings. I wonder if it's safe to ignore some of them?
> Here is a list of warnings I got:
> -Wbitwise-op-parentheses
> -Wdangling-else
> -Wignored-attributes
> -Wlogical-op-parentheses
> -Wparentheses
> -Wshift-op-parentheses
> -Wstring-plus-int

All of these except -Wignored-attributes are style warnings we don't
attempt to follow. Whatever is triggering -Wignored-attributes in
clang might be an issue we should address.

> -Wunknown-pragmas

This one is definitely bad because gcc and clang fail to implement
some pragmas the standard requires to exist -- ones for floating point
environment stuff. With the right CFLAGS, the default behavior mostly
matches what the pragmas are trying to get and everything is okay, but
for source-level correctness they need to be there.

> Which of them should be ignored when building with clang? What are
> better be fixed?

I'd like to make this more clearly documented and automatically setup
by configure. The intended warnings are what you get with gcc and
passing --enable-warnings to configure, which uses -Wall then disables
ones that are noise, arbitrary style rules, etc. I think it should be
switched around to avoid -Wall, instead starting with -w for non-gcc
compilers and blank for gcc (since -w overrides later -W on gcc), then
explicitly adding the warning options we want to check against. Right
now, the only way to get that list is reading the gcc documentation
for -Wall and subtracting off the -Wno-*'s that musl's configure adds.


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