bug#20338: configure test for nopie with gcc 4.4.3 on Trisquel 4.1

bug#20338: configure test for nopie with gcc 4.4.3 on Trisquel 4.1

[Glenn Morris]

Package: emacs
Version: 25.0.50

On fencepost.gnu.org, I noticed the following oddity in config.log:

    configure:30326: checking whether gcc -std=gnu99 accepts -nopie
    configure:30346: gcc -std=gnu99 -o conftest -g3 -O2 -Werror -nopie conftest.c   >&5 
    gcc: unrecognized option '-nopie'
    configure:30346: $? = 0
    configure:30356: result: yes

cat /etc/issue
Trisquel GNU/Linux 4.1 \n \l

gcc --version
gcc (Ubuntu 4.4.3-4ubuntu5.1) 4.4.3

cat test.c
int main ()
 {
   return 0;
 }

gcc -std=gnu99 -o conftest -g3 -O2 -Werror -nopie test.c
gcc: unrecognized option '-nopie'

echo $?
0


Seems odd. Whereas:

gcc -std=gnu99 -o conftest -g3 -O2 -Werror  -foobar test.c
cc1: error: unrecognized command line option "-foobar"

echo $?
1

bug#20338: configure test for nopie with gcc 4.4.3 on Trisquel 4.1

[Glenn Morris]

IIUC, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=15303 says that you
can't reliably use the exit status of gcc to check whether it supports
a command-line option prior to gcc 4.6. Whee.

bug#20338: configure test for nopie with gcc 4.4.3 on Trisquel 4.1

[Paul Eggert]

[-- Attachment #1: Type: text/plain, Size: 148 bytes --]

Thanks for reporting that.  In master commit 
c6e93df20266fe9f8517f14f3b7c367281f988a5 I installed the attached patch, which 
fixed the bug for me.

[-- Attachment #2: 0001-Pre-4.6-GCC-succeeds-with-unknown-option.patch --]
[-- Type: text/x-patch, Size: 1636 bytes --]

From aefb6f4a4b4bc59386d817728760a15e1225aa6f Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 16 Apr 2015 00:14:11 -0700
Subject: [PATCH] Pre-4.6 GCC succeeds with unknown option

* configure.ac (emacs_cv_prog_cc_nopie): Port to pre-4.6 GCC.
Fixes: bug#20338
---
 configure.ac | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/configure.ac b/configure.ac
index c35e962..39f3f9f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5021,18 +5021,19 @@ esac
 # -nopie fixes a temacs segfault on Gentoo, OpenBSD, and other systems
 # with "hardened" GCC configurations for some reason (Bug#18784).
 # We don't know why -nopie works, but not segfaulting is better than
-# segfaulting.  Use -Werror when trying -nopie, otherwise clang keeps
-# warning that it does not understand -nopie.
+# segfaulting.  Use ac_c_werror_flag=yes when trying -nopie, otherwise
+# clang keeps warning that it does not understand -nopie, and pre-4.6
+# GCC has a similar problem (Bug#20338).
 AC_CACHE_CHECK([whether $CC accepts -nopie],
   [emacs_cv_prog_cc_nopie],
-  [emacs_save_CFLAGS=$CFLAGS
+  [emacs_save_c_werror_flag=$ac_c_werror_flag
    emacs_save_LDFLAGS=$LDFLAGS
-   CFLAGS="$CFLAGS -Werror"
+   ac_c_werror_flag=yes
    LDFLAGS="$LDFLAGS -nopie"
    AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])],
      [emacs_cv_prog_cc_nopie=yes],
      [emacs_cv_prog_cc_nopie=no])
-   CFLAGS=$emacs_save_CFLAGS
+   ac_c_werror_flag=$emacs_save_c_werror_flag
    LDFLAGS=$emacs_save_LDFLAGS])
 if test "$emacs_cv_prog_cc_nopie" = yes; then
   LD_SWITCH_SYSTEM_TEMACS="$LD_SWITCH_SYSTEM_TEMACS -nopie"
-- 
2.1.0