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Date: Sun, 31 May 2015 23:18:29 -0400
From: Rich Felker <>
Subject: Re: [PATCH 2/2] build: overhaul wrapper script system for
 multiple wrapper support

On Fri, May 29, 2015 at 06:55:12PM +0200, Shiz wrote:
> this overhauls part of the build system in order to support multiple
> toolchain wrapper scripts, as opposed to solely the musl-gcc wrapper as
> before. it thereby replaces --enable-gcc-wrapper with --enable-wrapper=...,
> which has the options 'auto' (the default, detect whether to use wrappers),
> 'all' (build and install all wrappers), 'no' (don't build any) and finally
> the options named after the individual compiler scripts (currently 'clang'
> and 'gcc' are available) to build and install only that wrapper.
> the old --enable-gcc-wrapper is removed from --help, but still available.
> it also modifies the wrappers to use the C compiler specified to the build
> system as 'inner' compiler, when applicable. as wrapper detection works by
> probing this compiler, it may not work with any other.

I believe there's still some change of behavior here that also
violates the principle of least surprise:

For the old option:

yes -- forcibly build wrapper regardless of
compiler or existing-musl-target detection

auto -- build depends on 2 conditions: $CC being gcc and not being

no -- never build

For the new option:

yes or auto (same) -- build of gcc wrapper depends on 2 conditions:
$CC being gcc and not being musl-targeted. build of clang wrapper
depends only on one condition: $CC being clang.

gcc - unconditionally build gcc wrapper, never build clang wrapper

clang - unconditionally build clang wrapper, never build gcc wrapper

no -- never build

The most surprising part, which I think really should be fixed before
this is committed, is that the clang wrapper is built if you compile
musl with clang on a musl-native system. (Note that the gcc test right
now for musl-native is also wrong if the gcc toolchain omits dynamic
linking support entirely, but that's an existing bug, not a

Even if that's fixed, it's also a problem, I think, that yes/auto are
equated. Presumably someone using --enable-wrapper with an existing
musl-targeted toolchain would want to bypass the musl-native detection
and force the wrapper (whichever one is appropriate for their
compiler) to be built. This is especially important to have if the
musl-native test has false positives, which I think it will if we take
the following approach I'd like to take:

Instead of testing for musl-native, test whether the toolchain is
targetting another known non-musl target, which is basically a matter
of #ifdef __GLIBC__. This ensures that the wrapper is never auto-built
for a musl-native system (which could happen before if the musl-native
test failed) and avoids compiler-specific hacks; we can simply have a
general test for known-non-native-toolchain.

If this is acceptable, it would probably make sense to do this change
before adding the clang wrapper infrastructure so that the clang
wrapper tests can use the result of it.


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