[FFmpeg-devel] [PATCH 2/2] When checking for compiler or linker flags, check if warnings are reported.

[Måns Rullgård]

Diego 'Flameeyes' Petten? wrote:
> Not all compilers and linkres fail with error when an option they
> don't support is used during compilation or linking. For instance, the
> Sun Studio and the Intel compiler suites, only issue warnings for
> those cases.
>
> Also, even GCC only issues warnings when a flag that cannot be used
> with a given language (like -fvisibility-inlines-hidden used with the
> C frontend).
>
> With this patch, the checks for both compiler and linker flags will
> ensure that no warning is issued that might show the compiler or
> linker doesn't support the flag being tested. This will avoid adding
> further warnings during build.
>
> Further changes: when identifying the Intel C Compiler, further flags
> were added to disable the warnings issued by the unsupported flags;
> since this check disallows those from being added in the CFLAGS
> variable in the first place, remove them, so that actually unsupported
> flags used but not checked for will issue a warning.
>
> Known possible issue: it expects the user to know its compiler and not
> forcing through --extra-cflags or --extra-ldflags options that are not
> supported, otherwise all the cflags/ldflags checks will fail. Doesn't
> look too bad.
> ---
>
>  configure |   37 +++++++++++++++++++++++++++----------
>  1 files changed, 27 insertions(+), 10 deletions(-)
>
> diff --git a/configure b/configure
> index 349464e..8ead633 100755
> --- a/configure
> +++ b/configure
> @@ -226,7 +226,7 @@ Include the log file "$logfile" produced by configure as
> this will help
>  solving the problem.
>  EOF
>      fi
> -    rm -f $TMPC $TMPE $TMPH $TMPO $TMPS $TMPSH
> +    rm -f $TMPC $TMPE $TMPH $TMPO $TMPS $TMPSH $TMPLOG $TMPRES
>      exit 1
>  }
>
> @@ -423,7 +423,9 @@ add_extralibs(){
>
>  check_cmd(){
>      log "$@"
> -    "$@" >> $logfile 2>&1
> +    rm -f $TMPRES
> +    ( "$@" 2>&1 && touch $TMPRES; ) | tee $TMPLOG >> $logfile
> +    test -f $TMPRES
>  }

I still don't like this.  I have half an idea that I'll test later.  I'm
tied up offline stuff the rest of this week, so a gentle reminder when I
next show up on IRC would be in order.

>  check_cc(){
> @@ -471,16 +473,34 @@ check_ld(){
>
>  check_cflags(){
>      log check_cflags "$@"
> -    check_cc "$@" <<EOF && add_cflags "$@"
> +    check_cc "$@" <<EOF || return 1
>  int x;
>  EOF
> +
> +    grep -qi "warning" $TMPLOG && return 1
> +    grep -qi "illegal option" $TMPLOG && return 1
> +    grep -qi "unknown option" $TMPLOG && return 1
> +    grep -qi "ignoring option" $TMPLOG && return 1
> +    grep -qi "unrecognized" $TMPLOG && return 1
> +
> +    add_cflags "$@"
> +    return 0
>  }
>
>  check_ldflags(){
>      log check_ldflags "$@"
> -    check_ld "$@" <<EOF && add_ldflags "$@"
> +    check_ld "$@" <<EOF || return 1
>  int main(void){ return 0; }
>  EOF
> +
> +    grep -qi "warning" $TMPLOG && return 1
> +    grep -qi "illegal option" $TMPLOG && return 1
> +    grep -qi "unknown option" $TMPLOG && return 1
> +    grep -qi "ignoring option" $TMPLOG && return 1
> +    grep -qi "unrecognized" $TMPLOG && return 1
> +
> +    add_ldflags "$@"
> +    return 0
>  }

Either I've become cross-eyed, or that's duplicated code.

>  check_header(){
> @@ -1132,6 +1152,8 @@ TMPH="${TMPDIR1}/ffmpeg-conf-${RANDOM}-$$-${RANDOM}.h"
>  TMPO="${TMPDIR1}/ffmpeg-conf-${RANDOM}-$$-${RANDOM}.o"
>  TMPS="${TMPDIR1}/ffmpeg-conf-${RANDOM}-$$-${RANDOM}.S"
>  TMPSH="${TMPDIR1}/ffmpeg-conf-${RANDOM}-$$-${RANDOM}.sh"
> +TMPLOG="${TMPDIR1}/ffmpeg-conf-${RANDOM}-$$-${RANDOM}.log"
> +TMPRES="${TMPDIR1}/ffmpeg-conf-${RANDOM}-$$-${RANDOM}.res"
>
>  check_cflags -fasm
>  check_cflags -std=c99
> @@ -1891,12 +1913,7 @@ if $cc --version | grep -q Intel; then
>    check_cflags -w1
>    # -wd: Disable following warnings
>    # 144, 167, 556: -Wno-pointer-sign
> -  # 10006: ignoring unknown option -fno-signed-zeros
> -  # 10156: ignoring option '-W'; no argument required
> -  check_cflags -wd144,167,556,10006,10156
> -  # 11030: Warning unknown option --as-needed
> -  # 10156: ignoring option '-export'; no argument required
> -  check_ldflags -wd10156,11030
> +  check_cflags -wd144,167,556
>    # Allow to compile with optimizations
>    check_ldflags -march=$cpu
>  fi

This should arguably be done separately.

-- 
M?ns Rullg?rd
mans at mansr.com