>From ebe69201526d403a81d1dba2896b514b2f00dc29 Mon Sep 17 00:00:00 2001
From: Nikolai Merinov <nikolai.merinov@member.fsf.org>
Date: Thu, 7 Mar 2019 22:33:13 +0500
Subject: [PATCH] _AC_DO _AC_DO_STDERR: Evaluate argument twice

The `AC_COMPILE_IFELSE', `AC_LINK_IFELSE', `AC_PREPROC_IFELSE' macros
use the `_AC_DO_STDERR` macro in the following manner:

> ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> _AC_DO_STDERR($ac_compile) # Unescape variable only once

Full compilation process works like the following:

> CFLAGS='-DFLAG=\"quoted string\"' ./configure
> # Produce Makefile with CFLAGS = -DFLAG=\"quoted string\"
> make # substitute args in "$(CC) $(CFLAGS) ..." recipe and call shell
> gcc -DFLAG="quoted string" ... # Arg was evaluated twice

In order to have same behavior during a configuration stage and during
a compilation stage we should evaluate a passed argument twice in
_AC_DO_STDERR command: in second time we'll be able to unquote strings
in user-supplied variables as it happens during make rules execution.

The `_AC_DO' macro used through the `_AC_DO_VAR' macro in similar
manner in many places and should work by same rules.

* lib/autoconf/general.m4 (_AC_DO_STDERR): Reuse `_AC_DO_ECHO' trick
to evaluate arguments twice if compile string have no '\"', '`', or
'\\' symbols.
  (_AC_DO): Same changes.
* tests/compile.at: Add test for CFLAGS evaluation.
---
 NEWS                    |  6 ++++++
 lib/autoconf/general.m4 | 22 ++++++++++++++++++----
 tests/compile.at        | 13 +++++++++++++
 3 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/NEWS b/NEWS
index dbbea222..b637b2e3 100644
--- a/NEWS
+++ b/NEWS
@@ -229,6 +229,12 @@ GNU Autoconf NEWS - User visible changes.
   subdirectory.  See the documentation of AC_OPENMP for further
   explanation.
 
+*** The _AC_DO_STDERR and _AC_DO macros now evaluate a COMMAND argument twice.
+
+  This change consolidate behavior for user-supplied arguments
+  between the AC_COMPILE_IFELSE and AC_LINK_IFELSE macros and
+  compilation commands used in makefiles.
+
 ** New features
 
 *** Configure scripts now support a ‘--runstatedir’ option.
diff --git a/lib/autoconf/general.m4 b/lib/autoconf/general.m4
index 16f0d074..1fecffdb 100644
--- a/lib/autoconf/general.m4
+++ b/lib/autoconf/general.m4
@@ -2607,16 +2607,30 @@ AS_ECHO(["$ac_try_echo"])])
 # Eval COMMAND, save the exit status in ac_status, and log it.
 # For internal use only.
 AC_DEFUN([_AC_DO],
-[_AC_RUN_LOG([eval "$1"],
-	     [_AC_DO_ECHO([$1])])])
+[m4_if([$1], [$ac_do], [], [ac_do="$1"
+])]dnl
+[[case "(($ac_do" in
+  *\"* | *\`* | *\\*) ac_do_command=\$ac_do;;
+  *) ac_do_command=$ac_do;;
+esac
+eval ac_do_command="\"$ac_do_command\""]
+_AC_RUN_LOG([eval "$ac_do_command"],
+		   [_AC_DO_ECHO([$ac_do])])])
 
 
 # _AC_DO_STDERR(COMMAND)
 # ----------------------
 # Like _AC_RUN_LOG_STDERR, but eval (instead of running) COMMAND.
 AC_DEFUN([_AC_DO_STDERR],
-[_AC_RUN_LOG_STDERR([eval "$1"],
-		    [_AC_DO_ECHO([$1])])])
+[m4_if([$1], [$ac_do_stderr], [], [ac_do_stderr="$1"
+])]dnl
+[[case "(($ac_do_stderr" in
+  *\"* | *\`* | *\\*) ac_do_stderr_command=\$ac_do_stderr;;
+  *) ac_do_stderr_command=$ac_do_stderr;;
+esac
+eval ac_do_stderr_command="\"$ac_do_stderr_command\""]
+_AC_RUN_LOG_STDERR([eval "$ac_do_stderr_command"],
+		   [_AC_DO_ECHO([$ac_do_stderr])])])
 
 
 # _AC_DO_VAR(VARIABLE)
diff --git a/tests/compile.at b/tests/compile.at
index 4847f111..5eeadd6d 100644
--- a/tests/compile.at
+++ b/tests/compile.at
@@ -302,6 +302,19 @@ AC_OUTPUT
 AT_CHECK_AUTOCONF
 AT_CHECK_CONFIGURE([-q])
 
+AT_DATA([configure.ac],
+[[AC_INIT
+AC_PROG_CC
+test x$GCC = xyes && CFLAGS='"-Wall"'
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [return 0])],
+	      [],
+	      [AC_MSG_ERROR([compiling program with quoted CFLAGS failed])])
+AC_OUTPUT
+]])
+
+AT_CHECK_AUTOCONF
+AT_CHECK_CONFIGURE([-q])
+
 AT_CLEANUP
 
 ## --------------- ##
-- 
2.29.2