On Tue, Sep 27, 2016 at 3:05 PM, Marek Polacek <pola...@redhat.com> wrote:
> Using -Wno-error where only -Wno-implicit-fallthrough was meant was deemed
> to coarse, so this patch attempts to add a configure check for this warnign
> and only use -Wno-implicit-fallthrough when appropriate.
>
> Bootstrapped on x86_64-linux and ppc64-linux, ok for trunk?
It looks to me this would hide eventual bugs in .md files by not
issueing the warning?
Richard.
> 2016-09-27 Marek Polacek <pola...@redhat.com>
>
> * Makefile.in (insn-attrtab.o-warn, insn-dfatab.o-warn,
> insn-latencytab.o-warn, insn-output.o-warn, insn-emit.o-warn): Use
> @W_NO_IMPLICIT_FALLTHROUGH@ instead of -Wno-error.
> * configure.ac: Add check for -Wimplicit-fallthrough.
> * configure: Regenerate.
>
> diff --git a/gcc/Makefile.in b/gcc/Makefile.in
> index ff12908..5871a47 100644
> --- a/gcc/Makefile.in
> +++ b/gcc/Makefile.in
> @@ -218,11 +218,11 @@ libgcov-merge-tool.o-warn = -Wno-error
> gimple-match.o-warn = -Wno-unused
> generic-match.o-warn = -Wno-unused
> dfp.o-warn = -Wno-strict-aliasing
> -insn-attrtab.o-warn = -Wno-error
> -insn-dfatab.o-warn = -Wno-error
> -insn-latencytab.o-warn = -Wno-error
> -insn-output.o-warn = -Wno-error
> -insn-emit.o-warn = -Wno-error
> +insn-attrtab.o-warn = @W_NO_IMPLICIT_FALLTHROUGH@
> +insn-dfatab.o-warn = @W_NO_IMPLICIT_FALLTHROUGH@
> +insn-latencytab.o-warn = @W_NO_IMPLICIT_FALLTHROUGH@
> +insn-output.o-warn = @W_NO_IMPLICIT_FALLTHROUGH@
> +insn-emit.o-warn = @W_NO_IMPLICIT_FALLTHROUGH@
>
> # All warnings have to be shut off in stage1 if the compiler used then
> # isn't gcc; configure determines that. WARN_CFLAGS will be either
> diff --git a/gcc/configure b/gcc/configure
> index 96eba9e..459f513 100755
> --- a/gcc/configure
> +++ b/gcc/configure
> @@ -789,6 +789,7 @@ valgrind_path
> TREECHECKING
> nocommon_flag
> noexception_flags
> +W_NO_IMPLICIT_FALLTHROUGH
> warn_cxxflags
> warn_cflags
> c_strict_warn
> @@ -7006,6 +7007,34 @@ fi
>
>
>
> +# Check whether -Wimplicit-fallthrough works.
> +W_NO_IMPLICIT_FALLTHROUGH=
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for -Wimplicit-fallthrough
> option" >&5
> +$as_echo_n "checking for -Wimplicit-fallthrough option... " >&6; }
> +if test "${gcc_cv_implicit_fallthrough+set}" = set; then :
> + $as_echo_n "(cached) " >&6
> +else
> + saved_CXXFLAGS="$CXXFLAGS"
> + CXXFLAGS="$CXXFLAGS -Wimplicit-fallthrough"
> + cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> +/* end confdefs.h. */
> +int main(void) {return 0;}
> +_ACEOF
> +if ac_fn_cxx_try_compile "$LINENO"; then :
> + gcc_cv_implicit_fallthrough=yes
> +else
> + gcc_cv_implicit_fallthrough=no
> +fi
> +rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> + CXXFLAGS="$saved_CXXFLAGS"
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result:
> $gcc_cv_implicit_fallthrough" >&5
> +$as_echo "$gcc_cv_implicit_fallthrough" >&6; }
> +if test "$gcc_cv_implicit_fallthrough" = "yes"; then
> + W_NO_IMPLICIT_FALLTHROUGH="-Wno-implicit-fallthrough"
> +fi
> +
> +
> # Disable exceptions and RTTI if building with g++
> ac_ext=c
> ac_cpp='$CPP $CPPFLAGS'
> @@ -18476,7 +18505,7 @@ else
> lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
> lt_status=$lt_dlunknown
> cat > conftest.$ac_ext <<_LT_EOF
> -#line 18479 "configure"
> +#line 18508 "configure"
> #include "confdefs.h"
>
> #if HAVE_DLFCN_H
> @@ -18582,7 +18611,7 @@ else
> lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
> lt_status=$lt_dlunknown
> cat > conftest.$ac_ext <<_LT_EOF
> -#line 18585 "configure"
> +#line 18614 "configure"
> #include "confdefs.h"
>
> #if HAVE_DLFCN_H
> diff --git a/gcc/configure.ac b/gcc/configure.ac
> index 534f22e..b72e52a 100644
> --- a/gcc/configure.ac
> +++ b/gcc/configure.ac
> @@ -503,6 +503,21 @@ fi
> AC_SUBST(warn_cflags)
> AC_SUBST(warn_cxxflags)
>
> +# Check whether -Wimplicit-fallthrough works.
> +W_NO_IMPLICIT_FALLTHROUGH=
> +AC_CACHE_CHECK([for -Wimplicit-fallthrough option],
> + [gcc_cv_implicit_fallthrough],
> + [saved_CXXFLAGS="$CXXFLAGS"
> + CXXFLAGS="$CXXFLAGS -Wimplicit-fallthrough"
> + AC_COMPILE_IFELSE([int main(void) {return 0;}],
> + [gcc_cv_implicit_fallthrough=yes],
> + [gcc_cv_implicit_fallthrough=no])
> + CXXFLAGS="$saved_CXXFLAGS"])
> +if test "$gcc_cv_implicit_fallthrough" = "yes"; then
> + W_NO_IMPLICIT_FALLTHROUGH="-Wno-implicit-fallthrough"
> +fi
> +AC_SUBST([W_NO_IMPLICIT_FALLTHROUGH])
> +
> # Disable exceptions and RTTI if building with g++
> ACX_PROG_CC_WARNING_OPTS(
> m4_quote(m4_do([-fno-exceptions -fno-rtti
> -fasynchronous-unwind-tables])),
>
> Marek
