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

[Diego 'Flameeyes' Pettenò]

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.

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 |   26 ++++++++++++++++++++++----
 1 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/configure b/configure
index 0a31571..ee4ab1f 100755
--- a/configure
+++ b/configure
@@ -223,7 +223,7 @@ 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
 }
 
@@ -420,7 +420,9 @@ add_extralibs(){
 
 check_cmd(){
     log "$@"
-    "$@" >> $logfile 2>&1
+    rm -f $TMPRES
+    ( "$@" 2>&1 && touch $TMPRES; ) | tee $TMPLOG >> $logfile
+    test -f $TMPRES
 }
 
 check_cc(){
@@ -466,18 +468,32 @@ check_ld(){
     check_cmd $cc $LDFLAGS $flags -o $TMPE $TMPO $extralibs $libs
 }
 
+check_flags_warning() {
+    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" $TMPLOG && return 1
+
+    return 0
+}
+
 check_cflags(){
     log check_cflags "$@"
-    check_cc "$@" <<EOF && add_cflags "$@"
+    check_cc "$@" <<EOF || return 1
 int x;
 EOF
+
+    check_flags_warning && add_cflags "$@"
 }
 
 check_ldflags(){
     log check_ldflags "$@"
-    check_ld "$@" <<EOF && add_ldflags "$@"
+    check_ld "$@" <<EOF || return 1
 int main(void){ return 0; }
 EOF
+
+    check_flags_warning && add_ldflags "$@"
 }
 
 check_header(){
@@ -1125,6 +1141,8 @@ 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