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Re: [PATCH] Fix -Wno-unknown-warning support detection
- From: Simon Marchi <simon dot marchi at ericsson dot com>
- To: Pedro Alves <palves at redhat dot com>, <gdb-patches at sourceware dot org>
- Date: Wed, 16 Dec 2015 18:07:54 -0500
- Subject: Re: [PATCH] Fix -Wno-unknown-warning support detection
- Authentication-results: sourceware.org; auth=none
- References: <1450306675-8885-1-git-send-email-palves at redhat dot com>
On 15-12-16 05:57 PM, Pedro Alves wrote:
> Ref: https://sourceware.org/ml/gdb/2015-12/msg00024.html
>
> We have code in configure.ac that tries to detect whether the compiler
> supports each warning and suppress it if not, but that doesn't work
> with "-Wno-" options, because gcc doesn't error out for
> -Wno-unknown-warning unless other diagnostics are being produced.
>
> See https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html.
>
> Handle this by checking whether -Wfoo works when we actually want
> -Wno-foo.
>
> gdb/ChangeLog:
> 2015-12-16 Pedro Alves <palves@redhat.com>
>
> * configure.ac (compiler warning flags): When testing a
> -Wno-foo option, check whether -Wfoo works instead.
> * configure: Regenerate.
>
> gdb/gdbserver/ChangeLog:
> 2015-12-16 Pedro Alves <palves@redhat.com>
>
> * configure.ac (compiler warning flags): When testing a
> -Wno-foo option, check whether -Wfoo works instead.
> * configure: Regenerate.
> ---
> gdb/configure | 13 +++++++++++--
> gdb/configure.ac | 13 +++++++++++--
> gdb/gdbserver/configure | 13 +++++++++++--
> gdb/gdbserver/configure.ac | 13 +++++++++++--
> 4 files changed, 44 insertions(+), 8 deletions(-)
>
> diff --git a/gdb/configure b/gdb/configure
> index 249a399..4c308cb 100755
> --- a/gdb/configure
> +++ b/gdb/configure
> @@ -14376,14 +14376,23 @@ $as_echo_n "checking compiler warning flags... " >&6; }
> # Separate out the -Werror flag as some files just cannot be
> # compiled with it enabled.
> for w in ${build_warnings}; do
> + # GCC does not complain about -Wno-unknown-warning. Invert
> + # and test -Wunknown-warning instead.
> + case $w in
> + -Wno-*)
> + wtest=`echo $w | sed 's/-Wno-/-W/g'` ;;
> + *)
> + wtest=$w ;;
> + esac
> +
> case $w in
> -Werr*) WERROR_CFLAGS=-Werror ;;
> *)
> # Check whether GCC accepts it.
> saved_CFLAGS="$CFLAGS"
> - CFLAGS="$CFLAGS $w"
> + CFLAGS="$CFLAGS $wtest"
> saved_CXXFLAGS="$CXXFLAGS"
> - CXXFLAGS="$CXXFLAGS $w"
> + CXXFLAGS="$CXXFLAGS $wtest"
> cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> /* end confdefs.h. */
>
> diff --git a/gdb/configure.ac b/gdb/configure.ac
> index ebd797b..b9d8f8b 100644
> --- a/gdb/configure.ac
> +++ b/gdb/configure.ac
> @@ -2007,14 +2007,23 @@ then
> # Separate out the -Werror flag as some files just cannot be
> # compiled with it enabled.
> for w in ${build_warnings}; do
> + # GCC does not complain about -Wno-unknown-warning. Invert
> + # and test -Wunknown-warning instead.
> + case $w in
> + -Wno-*)
> + wtest=`echo $w | sed 's/-Wno-/-W/g'` ;;
> + *)
> + wtest=$w ;;
> + esac
> +
> case $w in
> -Werr*) WERROR_CFLAGS=-Werror ;;
> *)
> # Check whether GCC accepts it.
> saved_CFLAGS="$CFLAGS"
> - CFLAGS="$CFLAGS $w"
> + CFLAGS="$CFLAGS $wtest"
> saved_CXXFLAGS="$CXXFLAGS"
> - CXXFLAGS="$CXXFLAGS $w"
> + CXXFLAGS="$CXXFLAGS $wtest"
> AC_TRY_COMPILE([],[],WARN_CFLAGS="${WARN_CFLAGS} $w",)
> CFLAGS="$saved_CFLAGS"
> CXXFLAGS="$saved_CXXFLAGS"
> diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
> index ccb9639..ab03cac 100755
> --- a/gdb/gdbserver/configure
> +++ b/gdb/gdbserver/configure
> @@ -6148,14 +6148,23 @@ $as_echo_n "checking compiler warning flags... " >&6; }
> # Separate out the -Werror flag as some files just cannot be
> # compiled with it enabled.
> for w in ${build_warnings}; do
> + # GCC does not complain about -Wno-unknown-warning. Invert
> + # and test -Wunknown-warning instead.
> + case $w in
> + -Wno-*)
> + wtest=`echo $w | sed 's/-Wno-/-W/g'` ;;
> + *)
> + wtest=$w ;;
> + esac
> +
> case $w in
> -Werr*) WERROR_CFLAGS=-Werror ;;
> *)
> # Check whether GCC accepts it.
> saved_CFLAGS="$CFLAGS"
> - CFLAGS="$CFLAGS $w"
> + CFLAGS="$CFLAGS $wtest"
> saved_CXXFLAGS="$CXXFLAGS"
> - CXXFLAGS="$CXXFLAGS $w"
> + CXXFLAGS="$CXXFLAGS $wtest"
> cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> /* end confdefs.h. */
>
> diff --git a/gdb/gdbserver/configure.ac b/gdb/gdbserver/configure.ac
> index 5524a05..6caf91c 100644
> --- a/gdb/gdbserver/configure.ac
> +++ b/gdb/gdbserver/configure.ac
> @@ -193,14 +193,23 @@ then
> # Separate out the -Werror flag as some files just cannot be
> # compiled with it enabled.
> for w in ${build_warnings}; do
> + # GCC does not complain about -Wno-unknown-warning. Invert
> + # and test -Wunknown-warning instead.
> + case $w in
> + -Wno-*)
> + wtest=`echo $w | sed 's/-Wno-/-W/g'` ;;
> + *)
> + wtest=$w ;;
> + esac
> +
> case $w in
> -Werr*) WERROR_CFLAGS=-Werror ;;
> *)
> # Check whether GCC accepts it.
> saved_CFLAGS="$CFLAGS"
> - CFLAGS="$CFLAGS $w"
> + CFLAGS="$CFLAGS $wtest"
> saved_CXXFLAGS="$CXXFLAGS"
> - CXXFLAGS="$CXXFLAGS $w"
> + CXXFLAGS="$CXXFLAGS $wtest"
> AC_TRY_COMPILE([],[],WARN_CFLAGS="${WARN_CFLAGS} $w",)
> CFLAGS="$saved_CFLAGS"
> CXXFLAGS="$saved_CXXFLAGS"
>
It looks good. Note that you could have done
wtest=`echo $w | sed 's/-Wno-/-W/g'`
unconditionally. If it doesn't match, it won't replace anything:
$ echo -Wlol | sed 's/-Wno-/-W/g'
-Wlol
$ echo -Wno-lol | sed 's/-Wno-/-W/g'
-Wlol