Fix configure check for veracity of compiler error return codes.

There were two problems before that this fixes.  One was that the
check for the compiler error return code preceded the determination
of the compiler and its options.  The other was that the checks
for compiler and library characteristics could be fooled if the
error options were set to reject K&R-style C.  configure now aborts
if the compiler produces a hard error on K&R-style C.

In addition, aborts of configure are now consistent, and remove
any temporary files.

configure

@@ -77,6 +77,19 @@ old_cflags="$CFLAGS"
 OBJC='$(OBJZ) $(OBJG)'
 PIC_OBJC='$(PIC_OBJZ) $(PIC_OBJG)'
 
+# leave this script, optionally in a bad way
+leave()
+{
+  if test "$*" != "0"; then
+    echo "** $0 aborting." | tee -a configure.log
+  fi
+  rm -f $test.[co] $test $test$shared_ext $test.gcno ./--version
+  echo -------------------- >> configure.log
+  echo >> configure.log
+  echo >> configure.log
+  exit $1
+}
+
 # process command line options
 while test $# -ge 1
 do
@@ -106,13 +119,17 @@ case "$1" in
     -a*=* | --archs=*) ARCHS=`echo $1 | sed 's/.*=//'`; shift ;;
     --sysconfdir=*) echo "ignored option: --sysconfdir" | tee -a configure.log; shift ;;
     --localstatedir=*) echo "ignored option: --localstatedir" | tee -a configure.log; shift ;;
-    *) echo "unknown option: $1"; echo "$0 --help for help" | tee -a configure.log; exit 1 ;;
+    *)
+      echo "unknown option: $1" | tee -a configure.log
+      echo "$0 --help for help" | tee -a configure.log
+      leave 1;;
     esac
 done
 
-# define functions for testing compiler and library characteristics and logging the results
+# temporary file name
 test=ztest$$
 
+# put arguments in log, also put test file in log if used in arguments
 show()
 {
   case "$*" in
@@ -124,43 +141,6 @@ show()
   echo $* >> configure.log
 }
 
-cat > $test.c <<EOF
-#error error
-EOF
-if ($CC -c $CFLAGS $test.c) 2>/dev/null; then
-  try()
-  {
-    show $*
-    test "`( $* ) 2>&1 | tee -a configure.log`" = ""
-  }
-  echo - using any output from compiler to indicate an error >> configure.log
-else
-  try()
-  {
-    show $*
-    ( $* ) >> configure.log 2>&1
-    ret=$?
-    if test $ret -ne 0; then
-      echo "(exit code "$ret")" >> configure.log
-    fi
-    return $ret
-  }
-fi
-
-tryboth()
-{
-  show $*
-  got=`( $* ) 2>&1`
-  ret=$?
-  printf %s "$got" >> configure.log
-  if test $ret -ne 0; then
-    return $ret
-  fi
-  test "$got" = ""
-}
-
-echo >> configure.log
-
 # check for gcc vs. cc and set compile and link flags based on the system identified by uname
 cat > $test.c <<EOF
 extern int getchar();
@@ -179,8 +159,8 @@ case `$cc -v 2>&1` in
   *gcc*) gcc=1 ;;
 esac
 
-show $cc -c $cflags $test.c
-if test "$gcc" -eq 1 && ($cc -c $cflags $test.c) >> configure.log 2>&1; then
+show $cc -c $test.c
+if test "$gcc" -eq 1 && ($cc -c $test.c) >> configure.log 2>&1; then
   echo ... using gcc >> configure.log
   CC="$cc"
   CFLAGS="${CFLAGS--O3} ${ARCHS}"
@@ -208,7 +188,7 @@ if test "$gcc" -eq 1 && ($cc -c $cflags $test.c) >> configure.log 2>&1; then
 # temporary bypass
         rm -f $test.[co] $test $test$shared_ext
         echo "Please use win32/Makefile.gcc instead." | tee -a configure.log
-        exit 1
+        leave 1
         LDSHARED=${LDSHARED-"$cc -shared"}
         LDSHAREDLIBC=""
         EXE='.exe' ;;
@@ -338,7 +318,59 @@ SHAREDLIBM=${SHAREDLIBM-"libz$shared_ext.$VER1"}
 
 echo >> configure.log
 
+# define functions for testing compiler and library characteristics and logging the results
+
+cat > $test.c <<EOF
+#error error
+EOF
+if ($CC -c $CFLAGS $test.c) 2>/dev/null; then
+  try()
+  {
+    show $*
+    test "`( $* ) 2>&1 | tee -a configure.log`" = ""
+  }
+  echo - using any output from compiler to indicate an error >> configure.log
+else
+try()
+{
+  show $*
+  ( $* ) >> configure.log 2>&1
+  ret=$?
+  if test $ret -ne 0; then
+    echo "(exit code "$ret")" >> configure.log
+  fi
+  return $ret
+}
+fi
+
+tryboth()
+{
+  show $*
+  got=`( $* ) 2>&1`
+  ret=$?
+  printf %s "$got" >> configure.log
+  if test $ret -ne 0; then
+    return $ret
+  fi
+  test "$got" = ""
+}
+
+cat > $test.c << EOF
+int foo() { return 0; }
+EOF
+echo "Checking for obsessive-compulsive compiler options..." >> configure.log
+if ! try $CC -c $CFLAGS $test.c; then
+  echo "Compiler error reporting is too harsh for $0 (perhaps remove -Werror)." | tee -a configure.log
+  leave 1
+fi
+
+echo >> configure.log
+
 # see if shared library build supported
+cat > $test.c <<EOF
+extern int getchar();
+int hello() {return getchar();}
+EOF
 if test $shared -eq 1; then
   echo Checking for shared library support... | tee -a configure.log
   # we must test in two steps (cc then ld), required at least on SunOS 4.x
@@ -366,8 +398,6 @@ else
   TEST="all teststatic testshared"
 fi
 
-echo >> configure.log
-
 # check for underscores in external names for use by assembler code
 CPP=${CPP-"$CC -E"}
 case $CFLAGS in
@@ -709,14 +739,14 @@ cat > $test.c <<EOF
 #include <stdio.h>
 #define is32(n,t) for(n=1,k=0;n;n<<=1,k++);if(k==32){puts(t);return 0;}
 int main() {
-    int k;
-    unsigned i;
-    unsigned long l;
-    unsigned short s;
-    is32(i, "unsigned")
-    is32(l, "unsigned long")
-    is32(s, "unsigned short")
-    return 1;
+  int k;
+  unsigned i;
+  unsigned long l;
+  unsigned short s;
+  is32(i, "unsigned")
+  is32(l, "unsigned long")
+  is32(s, "unsigned short")
+  return 1;
 }
 EOF
 Z_U4=""
@@ -728,9 +758,6 @@ else
   echo "Looking for a four-byte integer type... Not found." | tee -a configure.log
 fi
 
-# clean up files produced by running the compiler and linker
-rm -f $test.[co] $test $test$shared_ext $test.gcno ./--version
-
 # show the results in the log
 echo >> configure.log
 echo ALL = $ALL >> configure.log
@@ -762,9 +789,6 @@ echo mandir = $mandir >> configure.log
 echo prefix = $prefix >> configure.log
 echo sharedlibdir = $sharedlibdir >> configure.log
 echo uname = $uname >> configure.log
-echo -------------------- >> configure.log
-echo >> configure.log
-echo >> configure.log
 
 # udpate Makefile with the configure results
 sed < Makefile.in "
@@ -820,3 +844,6 @@ sed < zlib.pc.in "
 " | sed -e "
 s/\@VERSION\@/$VER/g;
 " > zlib.pc
+
+# done
+leave 0