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Message-ID: <f810b31d66fb3961b4b55442b66965eb72eaacdd.camel@klomp.org>
Subject: Re: V2 [PATCH] PKG_CHECK_MODULES: Check if $pkg_cv_[]$1[]_LIBS works
From: Mark Wielaard <mark@klomp.org>
To: "H.J. Lu" <hjl.tools@gmail.com>, Aaron Merey <amerey@redhat.com>
Cc: Simon Marchi <simark@simark.ca>, Tom Tromey <tom@tromey.com>, GCC
 Patches <gcc-patches@gcc.gnu.org>, Aaron Merey via Binutils
 <binutils@sourceware.org>,  GDB <gdb-patches@sourceware.org>
Date: Tue, 28 Jul 2020 14:54:11 +0200
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Hi,

On Mon, 2020-07-27 at 12:32 -0700, H.J. Lu via Binutils wrote:
> diff --git a/config/pkg.m4 b/config/pkg.m4
> index 13a8890178..45587e97c8 100644
> --- a/config/pkg.m4
> +++ b/config/pkg.m4
> @@ -147,6 +147,12 @@ AC_MSG_CHECKING([for $2])
>  _PKG_CONFIG([$1][_CFLAGS], [cflags], [$2])
>  _PKG_CONFIG([$1][_LIBS], [libs], [$2])
> =20
> +dnl Check whether $pkg_cv_[]$1[]_LIBS works.
> +pkg_save_LDFLAGS=3D"$LDFLAGS"
> +LDFLAGS=3D"$LDFLAGS $pkg_cv_[]$1[]_LIBS"
> +AC_TRY_LINK([],[return 0;], [pkg_failed=3Dno], [pkg_failed=3Dyes])
> +LDFLAGS=3D$pkg_save_LDFLAGS
> +
>  m4_define([_PKG_TEXT], [Alternatively, you may set the environment
> variables $1[]_CFLAGS
>  and $1[]_LIBS to avoid the need to call pkg-config.
>  See the pkg-config man page for more details.])

This hunk seems wrong. You are testing whether the $pkg_cv_[]$1[]_LIBS
flags work, but they might be empty if the library wasn't found
(pkg_failed=3Dyes). Then the AC_TRY_LINK will obviously succeed, and then
you set pkg_failed=3Dno. But that indicates that the library was found.

Cheers,

Mark