AC_PROG_WERROR

[Daniel Jacobowitz]

Outgrowth of my earlier conversation about GCC's configury.  This patch adds
an AC_PROG_WERROR macro which causes all compile, link, and preprocess
checks to fail on warnings.  How well this will work in practice, I'm not
100% sure.  My biggest concern would have been the warning messages for
glibc's stub functions; link checks for them would go from passing to
failing.  But there's already code to make them fail in the C compile check,
so I guess that's not a concern.  And the whole mode is optional anyway.

The patch is incomplete in a few ways, I suspect:
  - Should ac_flag_werror be initialized somewhere?
  - Should AC_PROG_CPP_WERROR be removed, since it was just added and this
    subsumes it?
  - Is AC_PROG_WERROR a good name?

But other than that this patch should be OK.  I've tested that it works as
expected, and I can build a correct libiberty using AC_PROG_WERROR. 
Thoughts?

I have one more patch for the upcoming autoconf release.  Coming right up.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

2003-10-01  Daniel Jacobowitz  <address@hidden>

        * lib/autoconf/general.m4 (AC_PROG_WERROR): New macro.
        (_AC_COMPILE_IFELSE, _AC_PREPROC_IFELSE, _AC_LINK_IFELSE): Check
        $ac_werror_flag.
        * doc/autoconf.texi (Generic Compiler Characteristics): Document
        AC_PROG_WERROR.

Index: doc/autoconf.texi
===================================================================
RCS file: /cvsroot/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.761
diff -u -p -r1.761 autoconf.texi
--- doc/autoconf.texi   26 Sep 2003 13:55:04 -0000      1.761
+++ doc/autoconf.texi   1 Oct 2003 21:05:29 -0000
@@ -384,7 +384,7 @@ Types
 Compilers and Preprocessors
 
 * Specific Compiler Characteristics::  Some portability issues
-* Generic Compiler Characteristics::  Language independent tests
+* Generic Compiler Characteristics::  Language independent tests and features
 * C Compiler::                  Checking its characteristics
 * C++ Compiler::                Likewise
 * Fortran 77 Compiler::         Likewise
@@ -5110,7 +5110,7 @@ compiling.
 
 @menu
 * Specific Compiler Characteristics::  Some portability issues
-* Generic Compiler Characteristics::  Language independent tests
+* Generic Compiler Characteristics::  Language independent tests and features
 * C Compiler::                  Checking its characteristics
 * C++ Compiler::                Likewise
 * Fortran 77 Compiler::         Likewise
@@ -5177,6 +5177,12 @@ AC_CHECK_SIZEOF(int *)
 defines @code{SIZEOF_INT_P} to be 8 on DEC Alpha AXP systems.
 @end defmac
 
address@hidden AC_PROG_WERROR
address@hidden
+Normally Autoconf ignores warnings generated by the compiler, linker,
+and preprocessor.  If this macro is used, warnings will be treated as
+fatal errors instead.
address@hidden defmac
 
 @node C Compiler
 @subsection C Compiler Characteristics
Index: lib/autoconf/general.m4
===================================================================
RCS file: /cvsroot/autoconf/autoconf/lib/autoconf/general.m4,v
retrieving revision 1.818
diff -u -p -r1.818 general.m4
--- lib/autoconf/general.m4     26 Sep 2003 09:11:23 -0000      1.818
+++ lib/autoconf/general.m4     1 Oct 2003 21:05:31 -0000
@@ -2030,7 +2030,11 @@ AC_DEFUN([AC_RUN_LOG],
 ## Examining declarations.  ##
 ## ------------------------ ##
 
-
+# AC_PROG_WERROR
+# ------------------
+# Treat warnings from the compiler and preprocessor as errors.
+AC_DEFUN([AC_PROG_WERROR],
+[ac_werror_flag=yes])# AC_PROG_WERROR
 
 # _AC_PREPROC_IFELSE(PROGRAM, [ACTION-IF-TRUE], [ACTION-IF-FALSE])
 # ----------------------------------------------------------------
@@ -2045,7 +2049,7 @@ AC_DEFUN([_AC_PREPROC_IFELSE],
 [m4_ifvaln([$1], [AC_LANG_CONFTEST([$1])])dnl
 if _AC_EVAL_STDERR([$ac_cpp conftest.$ac_ext]) >/dev/null; then
   if test -s conftest.err; then
-    ac_cpp_err=$ac_[]_AC_LANG_ABBREV[]_preproc_warn_flag
+    ac_cpp_err=$ac_[]_AC_LANG_ABBREV[]_preproc_warn_flag$ac_werror_flag
   else
     ac_cpp_err=
   fi
@@ -2127,7 +2131,8 @@ AC_DEFUN([AC_EGREP_HEADER],
 m4_define([_AC_COMPILE_IFELSE],
 [m4_ifvaln([$1], [AC_LANG_CONFTEST([$1])])dnl
 rm -f conftest.$ac_objext
-AS_IF([AC_TRY_EVAL(ac_compile) &&
+AS_IF([_AC_EVAL_STDERR($ac_compile) &&
+        AC_TRY_COMMAND([test -z "$ac_werror_flag" || test ! -s conftest.err]) 
&&
         AC_TRY_COMMAND([test -s conftest.$ac_objext])],
       [$2],
       [_AC_MSG_LOG_CONFTEST
@@ -2166,7 +2171,8 @@ AU_DEFUN([AC_TRY_COMPILE],
 m4_define([_AC_LINK_IFELSE],
 [m4_ifvaln([$1], [AC_LANG_CONFTEST([$1])])dnl
 rm -f conftest.$ac_objext conftest$ac_exeext
-AS_IF([AC_TRY_EVAL(ac_link) &&
+AS_IF([_AC_EVAL_STDERR($ac_link) &&
+        AC_TRY_COMMAND([test -z "$ac_werror_flag" || test ! -s conftest.err]) 
&&
         AC_TRY_COMMAND([test -s conftest$ac_exeext])],
       [$2],
       [_AC_MSG_LOG_CONFTEST