[FFmpeg-devel] [PATCH] Enhanced require_pkg_config() in configure to fallback to require() if pkg-config is missing

[James Almer]

On 4/13/2017 9:56 PM, Aaron Levinson wrote:
> From 48f7daba16e0fcdb83d9abd254800c7b9f4ab684 Mon Sep 17 00:00:00 2001
> From: Aaron Levinson <alevinsn at aracnet.com>
> Date: Thu, 13 Apr 2017 17:30:47 -0700
> Subject: [PATCH] Enhanced require_pkg_config() in configure to fallback to require() if pkg-config is missing
> 
> Purpose: Enhanced require_pkg_config() in configure to
> fallback to require() if pkg-config is missing
> 
> Notes: This is likely mainly of relevance when building with MSVC on
> Windows.  In my case, I used this approach to get libmfx when invoking
> configure with --enable-libmfx, which is used for QuickSync (QSV).
> 
> Comments:
> 
> -- configure: Enhanced require_pkg_config() function to first check if
>    $pkg_config is not false.  If not false, it goes through the
>    standard steps of calling use_pkg_config(), but if false, it issues
>    a log message and then calls require() with all the inputted
>    arguments and an additional argument: -l$1.  So, for something like
>    "require_pkg_config libmfx "mfx/mfxvideo.h" MFXInit", this becomes
>    "require libmfx "mfx/mfxvideo.h" MFXInit -llibmfx".  This is not a
>    perfect solution, but the previous approach didn't work at all
>    before when require_pkg_config() is used.
> ---
>  configure | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/configure b/configure
> index 7f2b653..ad08b82 100755
> --- a/configure
> +++ b/configure
> @@ -1347,7 +1347,12 @@ use_pkg_config(){
>  }
>  
>  require_pkg_config(){
> -    use_pkg_config "$@" || die "ERROR: $pkg not found using pkg-config$pkg_config_fail_message"
> +    if test $pkg_config != false; then
> +        use_pkg_config "$@" || die "ERROR: $pkg not found using pkg-config$pkg_config_fail_message"
> +    else
> +        log require_pkg_config "No pkg-config, using require for $@"
> +        require "$@ -l$1"
> +    fi

This will fail in a thousand ways with packages that require other
packages, specific cflags, specific ldflags, or that state specific
versions.
As Hendrik said, pkg-config is not just a fancy way to add -I and -L
options to the compiler and linker.