[neomutt-devel] [PATCH] fix check for no-delete-null-pointer-checks compiler flag

Roger Pau Monne roger.pau at citrix.com
Thu Sep 21 16:19:52 CEST 2017

Current check for no-delete-null-pointer-checks is bogus, introduce
AX_CHECK_COMPILE_FLAG and use it to check if
no-delete-null-pointer-checks is supported by the compiler.

This requires importing ax_check_compile_flag.m4 from
autoconf-archive, which is renamed to compiler_flags.m4 and placed in
the m4 subdirectory.
 configure.ac         |  5 ++--
 m4/compiler_flags.m4 | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 3 deletions(-)
 create mode 100644 m4/compiler_flags.m4

diff --git a/configure.ac b/configure.ac
index cf133e45..9b72b3de 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,9 +36,8 @@ if test "$ac_cv_prog_cc_c99" = "no"; then
 	AC_ERROR([Compiler does not support C99. Aborting.])
-if test "$CC" = "gcc"; then
-	CFLAGS="$CFLAGS -fno-delete-null-pointer-checks"
+	[CFLAGS="$CFLAGS -fno-delete-null-pointer-checks"], [], [-Werror])
 CFLAGS="-Wall -pedantic $CFLAGS"
diff --git a/m4/compiler_flags.m4 b/m4/compiler_flags.m4
new file mode 100644
index 00000000..dcabb92a
--- /dev/null
+++ b/m4/compiler_flags.m4
@@ -0,0 +1,74 @@
+# ===========================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
+# ===========================================================================
+#   Check whether the given FLAG works with the current language's compiler
+#   or gives an error.  (Warnings, however, are ignored)
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#   If EXTRA-FLAGS is defined, it is added to the current language's default
+#   flags (e.g. CFLAGS) when the check is done.  The check is thus made with
+#   the flags: "CFLAGS EXTRA-FLAGS FLAG".  This can for example be used to
+#   force the compiler to issue an error when a bad flag is given.
+#   INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
+#   macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG.
+#   Copyright (c) 2008 Guido U. Draheim <guidod at gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans at gmail.com>
+#   This program is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   Public License for more details.
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+#serial 5
+[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
+AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
+  ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
+  AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
+    [AS_VAR_SET(CACHEVAR,[yes])],
+    [AS_VAR_SET(CACHEVAR,[no])])
+  _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags])
+  [m4_default([$2], :)],
+  [m4_default([$3], :)])
2.13.5 (Apple Git-94)

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