Patchwork [toplevel] Check for warning flags without no- prefix

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Submitter Andreas Schwab
Date Dec. 18, 2011, 12:24 p.m.
Message ID <m2ehw29ieh.fsf@igel.home>
Download mbox | patch
Permalink /patch/132063/
State New
Headers show

Comments

Andreas Schwab - Dec. 18, 2011, 12:24 p.m.
Since gcc silently accepts any -Wno-* flag on purpose, it is ineffective
to check for support of a warning flag using the negative form.  Instead
always use the positive form when running the check (but keep the
original spelling for the result).

(Requires regeneration of fixincludes/configure gcc/configure
libcpp/configure libdecnumber/configure libiberty/configure
lto-plugin/configure)

Andreas.

2011-12-18  Andreas Schwab  <schwab@linux-m68k.org>

	* warnings.m4 (ACX_PROG_CC_WARNING_OPTS)
	(ACX_PROG_CC_WARNING_ALMOST_PEDANTIC): Run the test without the
	no- prefix.
Richard Guenther - Dec. 19, 2011, 9:09 a.m.
On Sun, Dec 18, 2011 at 1:24 PM, Andreas Schwab <schwab@linux-m68k.org> wrote:
> Since gcc silently accepts any -Wno-* flag on purpose, it is ineffective
> to check for support of a warning flag using the negative form.  Instead
> always use the positive form when running the check (but keep the
> original spelling for the result).
>
> (Requires regeneration of fixincludes/configure gcc/configure
> libcpp/configure libdecnumber/configure libiberty/configure
> lto-plugin/configure)

This is PR51388 btw.

Ok.

Thanks,
Richard.

> Andreas.
>
> 2011-12-18  Andreas Schwab  <schwab@linux-m68k.org>
>
>        * warnings.m4 (ACX_PROG_CC_WARNING_OPTS)
>        (ACX_PROG_CC_WARNING_ALMOST_PEDANTIC): Run the test without the
>        no- prefix.
>
> diff --git a/config/warnings.m4 b/config/warnings.m4
> index 3801c85..292e5a4 100644
> --- a/config/warnings.m4
> +++ b/config/warnings.m4
> @@ -1,6 +1,6 @@
>  # Autoconf include file defining macros related to compile-time warnings.
>
> -# Copyright 2004, 2005, 2007, 2009 Free Software Foundation, Inc.
> +# Copyright 2004, 2005, 2007, 2009, 2011 Free Software Foundation, Inc.
>
>  #This file is part of GCC.
>
> @@ -28,7 +28,13 @@ AC_SUBST(acx_Var)dnl
>  m4_expand_once([acx_Var=
>  ],m4_quote(acx_Var=))dnl
>  save_CFLAGS="$CFLAGS"
> -for option in $1; do
> +for real_option in $1; do
> +  # Do the check with the no- prefix removed since gcc silently
> +  # accepts any -Wno-* option on purpose
> +  case $real_option in
> +    -Wno-*) option=-W`expr $real_option : '-Wno-\(.*\)'` ;;
> +    *) option=$real_option ;;
> +  esac
>   AS_VAR_PUSHDEF([acx_Woption], [acx_cv_prog_cc_warning_$option])
>   AC_CACHE_CHECK([whether $CC supports $option], acx_Woption,
>     [CFLAGS="$option"
> @@ -37,14 +43,14 @@ for option in $1; do
>       [AS_VAR_SET(acx_Woption, no)])
>   ])
>   AS_IF([test AS_VAR_GET(acx_Woption) = yes],
> -        [acx_Var="$acx_Var${acx_Var:+ }$option"])
> +        [acx_Var="$acx_Var${acx_Var:+ }$real_option"])
>   AS_VAR_POPDEF([acx_Woption])dnl
>  done
>  CFLAGS="$save_CFLAGS"
>  m4_popdef([acx_Var])dnl
>  ])# ACX_PROG_CC_WARNING_OPTS
>
> -# ACX_PROG_CC_WARNING_ALMOST_PEDANTIC(WARNINGS, [VARIABLE = WARN_PEDANTIC)
> +# ACX_PROG_CC_WARNING_ALMOST_PEDANTIC(WARNINGS, [VARIABLE = WARN_PEDANTIC])
>  #   Append to VARIABLE "-pedantic" + the argument, if the compiler is GCC
>  #   and accepts all of those options simultaneously, otherwise to nothing.
>  AC_DEFUN([ACX_PROG_CC_WARNING_ALMOST_PEDANTIC],
> @@ -53,11 +59,14 @@ m4_pushdef([acx_Var], [m4_default([$2], [WARN_PEDANTIC])])dnl
>  AC_SUBST(acx_Var)dnl
>  m4_expand_once([acx_Var=
>  ],m4_quote(acx_Var=))dnl
> -AS_VAR_PUSHDEF([acx_Pedantic], [acx_cv_prog_cc_pedantic_$1])dnl
> +# Do the check with the no- prefix removed from the warning options
> +# since gcc silently accepts any -Wno-* option on purpose
> +m4_pushdef([acx_Woptions], [m4_bpatsubst([$1], [-Wno-], [-W])])dnl
> +AS_VAR_PUSHDEF([acx_Pedantic], [acx_cv_prog_cc_pedantic_]acx_Woptions)dnl
>  AS_IF([test "$GCC" = yes],
> -[AC_CACHE_CHECK([whether $CC supports -pedantic $1], acx_Pedantic,
> +[AC_CACHE_CHECK([whether $CC supports -pedantic ]acx_Woptions, acx_Pedantic,
>  [save_CFLAGS="$CFLAGS"
> -CFLAGS="-pedantic $1"
> +CFLAGS="-pedantic acx_Woptions"
>  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[])],
>    [AS_VAR_SET(acx_Pedantic, yes)],
>    [AS_VAR_SET(acx_Pedantic, no)])
> @@ -66,6 +75,7 @@ AS_IF([test AS_VAR_GET(acx_Pedantic) = yes],
>       [acx_Var="$acx_Var${acx_Var:+ }-pedantic $1"])
>  ])
>  AS_VAR_POPDEF([acx_Pedantic])dnl
> +m4_popdef([acx_Woptions])dnl
>  m4_popdef([acx_Var])dnl
>  ])# ACX_PROG_CC_WARNING_ALMOST_PEDANTIC
>
>
> --
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
> "And now for something completely different."

Patch

diff --git a/config/warnings.m4 b/config/warnings.m4
index 3801c85..292e5a4 100644
--- a/config/warnings.m4
+++ b/config/warnings.m4
@@ -1,6 +1,6 @@ 
 # Autoconf include file defining macros related to compile-time warnings.
 
-# Copyright 2004, 2005, 2007, 2009 Free Software Foundation, Inc.
+# Copyright 2004, 2005, 2007, 2009, 2011 Free Software Foundation, Inc.
 
 #This file is part of GCC.
 
@@ -28,7 +28,13 @@  AC_SUBST(acx_Var)dnl
 m4_expand_once([acx_Var=
 ],m4_quote(acx_Var=))dnl
 save_CFLAGS="$CFLAGS"
-for option in $1; do
+for real_option in $1; do
+  # Do the check with the no- prefix removed since gcc silently
+  # accepts any -Wno-* option on purpose
+  case $real_option in
+    -Wno-*) option=-W`expr $real_option : '-Wno-\(.*\)'` ;;
+    *) option=$real_option ;;
+  esac
   AS_VAR_PUSHDEF([acx_Woption], [acx_cv_prog_cc_warning_$option])
   AC_CACHE_CHECK([whether $CC supports $option], acx_Woption,
     [CFLAGS="$option"
@@ -37,14 +43,14 @@  for option in $1; do
       [AS_VAR_SET(acx_Woption, no)])
   ])
   AS_IF([test AS_VAR_GET(acx_Woption) = yes],
-        [acx_Var="$acx_Var${acx_Var:+ }$option"])
+        [acx_Var="$acx_Var${acx_Var:+ }$real_option"])
   AS_VAR_POPDEF([acx_Woption])dnl
 done
 CFLAGS="$save_CFLAGS"
 m4_popdef([acx_Var])dnl
 ])# ACX_PROG_CC_WARNING_OPTS
 
-# ACX_PROG_CC_WARNING_ALMOST_PEDANTIC(WARNINGS, [VARIABLE = WARN_PEDANTIC)
+# ACX_PROG_CC_WARNING_ALMOST_PEDANTIC(WARNINGS, [VARIABLE = WARN_PEDANTIC])
 #   Append to VARIABLE "-pedantic" + the argument, if the compiler is GCC
 #   and accepts all of those options simultaneously, otherwise to nothing.
 AC_DEFUN([ACX_PROG_CC_WARNING_ALMOST_PEDANTIC],
@@ -53,11 +59,14 @@  m4_pushdef([acx_Var], [m4_default([$2], [WARN_PEDANTIC])])dnl
 AC_SUBST(acx_Var)dnl
 m4_expand_once([acx_Var=
 ],m4_quote(acx_Var=))dnl
-AS_VAR_PUSHDEF([acx_Pedantic], [acx_cv_prog_cc_pedantic_$1])dnl
+# Do the check with the no- prefix removed from the warning options
+# since gcc silently accepts any -Wno-* option on purpose
+m4_pushdef([acx_Woptions], [m4_bpatsubst([$1], [-Wno-], [-W])])dnl
+AS_VAR_PUSHDEF([acx_Pedantic], [acx_cv_prog_cc_pedantic_]acx_Woptions)dnl
 AS_IF([test "$GCC" = yes],
-[AC_CACHE_CHECK([whether $CC supports -pedantic $1], acx_Pedantic,
+[AC_CACHE_CHECK([whether $CC supports -pedantic ]acx_Woptions, acx_Pedantic,
 [save_CFLAGS="$CFLAGS"
-CFLAGS="-pedantic $1"
+CFLAGS="-pedantic acx_Woptions"
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[])],
    [AS_VAR_SET(acx_Pedantic, yes)],
    [AS_VAR_SET(acx_Pedantic, no)])
@@ -66,6 +75,7 @@  AS_IF([test AS_VAR_GET(acx_Pedantic) = yes],
       [acx_Var="$acx_Var${acx_Var:+ }-pedantic $1"])
 ])
 AS_VAR_POPDEF([acx_Pedantic])dnl
+m4_popdef([acx_Woptions])dnl
 m4_popdef([acx_Var])dnl
 ])# ACX_PROG_CC_WARNING_ALMOST_PEDANTIC