Only write 'config-defs.h' if it has changed. Add -Wall and -pedantic to CFLAGS if they are supported by $(CC). Clean up test for -include flag.

configure.in

@@ -395,12 +395,13 @@ else
 fi  
 CC=$_SAVE_CC
 
-dnl Check for preprocesssor feature: command-line include files
-AC_MSG_CHECKING($CXX for \"-include <file>\" option)
+dnl Check cc for  -include flag support (command-line include files)
+dnl Assume that cxx has the feature if cc has it.
+dnl (We can add another test later if we need to.)
+AC_MSG_CHECKING($CC for \"-include <file>\" option)
 _tmp_header="include-test-$$.h"
 echo "char *booboo;" > $_tmp_header
 _SAVE_CFLAGS=$CFLAGS ; CFLAGS="$CFLAGS -include $_tmp_header"
-_SAVE_CC=$CC         ; CC=$CXX
 AC_CACHE_VAL(ac_cv_cxx_include_flag,
  [AC_TRY_COMPILE([],
                  [booboo = "yogi";],
@@ -408,27 +409,44 @@ AC_CACHE_VAL(ac_cv_cxx_include_flag,
                  [ac_cv_cxx_include_flag=false])])
 if test $ac_cv_cxx_include_flag = true ; then
   AC_MSG_RESULT(yes)
-else
-  AC_MSG_RESULT(no)
-fi  
-CC=$_SAVE_CC
-AC_MSG_CHECKING($CC for \"-include <file>\" option)
-AC_CACHE_VAL(ac_cv_cc_include_flag,
- [AC_TRY_COMPILE([],
-                 [booboo = "yogi";],
-                 [ac_cv_cc_include_flag=true],
-                 [ac_cv_cc_include_flag=false])])
-if test $ac_cv_cc_include_flag = true ; then
-  AC_MSG_RESULT(yes)
+  USE_CPP_INCLUDE_FLAG=1
+  AC_SUBST(USE_CPP_INCLUDE_FLAG)
 else
   AC_MSG_RESULT(no)
 fi  
 CFLAGS=$_SAVE_CFLAGS
-rm -r $_tmp_header
-if test $ac_cv_cc_include_flag = true -a $ac_cv_cxx_include_flag = true; then
-  USE_CPP_INCLUDE_FLAG=1
-  AC_SUBST(USE_CPP_INCLUDE_FLAG)
-fi
+
+dnl Check cc for -Wall flag support (adds compiler warnings)
+AC_MSG_CHECKING($CC for \"-Wall\" support)
+_SAVE_CFLAGS=$CFLAGS ; CFLAGS="$CFLAGS -Wall"
+AC_CACHE_VAL(ac_cv_cc_wall_flag,
+ [AC_TRY_COMPILE([],
+                 [int i;],
+                 [ac_cv_cc_wall_flag=true],
+                 [ac_cv_cc_wall_flag=false])])
+if test $ac_cv_cc_wall_flag = true ; then
+  AC_MSG_RESULT(yes)
+else
+  AC_MSG_RESULT(no)
+  dnl Take -Wall back off CFLAGS
+  CFLAGS=$_SAVE_CFLAGS
+fi  
+
+dnl Check cc for -pedantic flag support (adds compiler warnings)
+AC_MSG_CHECKING($CC for \"-pedantic\" support)
+_SAVE_CFLAGS=$CFLAGS ; CFLAGS="$CFLAGS -pedantic"
+AC_CACHE_VAL(ac_cv_cc_pedantic_flag,
+ [AC_TRY_COMPILE([],
+                 [int i;],
+                 [ac_cv_cc_pedantic_flag=true],
+                 [ac_cv_cc_pedantic_flag=false])])
+if test $ac_cv_cc_pedantic_flag = true ; then
+  AC_MSG_RESULT(yes)
+else
+  AC_MSG_RESULT(no)
+  dnl Take -pedantic back off CFLAGS
+  CFLAGS=$_SAVE_CFLAGS
+fi  
 
 # Mozilla specific options
 # ========================================================
@@ -991,7 +1009,7 @@ AC_CHECK_LIB(plds21, PL_GetEvent, NSPR_LIBS="-lplds21 $NSPR_LIBS",
 	[MISSING_NSPR="$MISSING_NSPR -lplds21"], $NSPR_LIBS)
 
 CFLAGS=$_SAVE_CFLAGS
-CFLAGS="${OPTIMIZE} ${GPROF} ${COMPILER_WARNINGS} ${CFLAGS}"
+CFLAGS="${OPTIMIZE} ${GPROF} ${CFLAGS}"
 LDFLAGS=$_SAVE_LDFLAGS
 LIBS=$_SAVE_LIBS
 
@@ -1064,14 +1082,20 @@ fi
 # (Do not add AC_DEFINE calls after this line.)
 if test "$USE_CPP_INCLUDE_FLAG"; then
   CONFIG_DEFS_H=config-defs.h
-  AC_MSG_RESULT("creating $CONFIG_DEFS_H")
-  cat > $CONFIG_DEFS_H <<\EOF
+  # Only write config-defs.h when something changes (or it doesn't exist)
+  if test ! -f $CONFIG_DEFS_H \
+     || diff confdefs.h $CONFIG_DEFS_H | grep \# > /dev/null; then
+    AC_MSG_RESULT("creating $CONFIG_DEFS_H")
+
+    cat > $CONFIG_DEFS_H <<\EOF
 /* List of defines generated by configure. Included with preprocessor flag,
  * -include, to avoid long list of -D defines on the compile command-line.
  * Do not edit.
  */
 EOF
-  cat confdefs.h >> $CONFIG_DEFS_H
+    cat confdefs.h >> $CONFIG_DEFS_H
+  fi
+
   CONFIG_DEFS_H='$(DEPTH)/'$CONFIG_DEFS_H
   AC_SUBST(CONFIG_DEFS_H)
 fi