configure: add internal sanity check (warn only) on vars for makefiles

configure.ac

@@ -3614,6 +3614,101 @@ squeeze CURL_NETWORK_AND_TIME_LIBS
 squeeze SUPPORT_FEATURES
 squeeze SUPPORT_PROTOCOLS
 
+dnl
+dnl Some sanity checks for LIBS, LDFLAGS, CPPFLAGS and CFLAGS values that
+dnl configure is going to feed into makefiles generated by automake. Due
+dnl to automake placement and usage of these variables we have to follow
+dnl its rules or we may get funny results later on at make-time.
+dnl
+
+dnl
+dnl LIBS should only specify libraries
+dnl
+AC_MSG_NOTICE([using LIBS: $LIBS])
+tst_bad_spec="no"
+for word1 in $LIBS; do
+  case "$word1" in
+    -l* | --library=*)
+      :
+      ;;
+    *)
+      tst_bad_spec="yes"
+      ;;
+  esac
+done
+if test "$tst_bad_spec" = "yes"; then
+  AC_MSG_WARN([oops, LIBS should only specify libraries.])
+fi
+
+dnl
+dnl LDFLAGS should only specify linker flags
+dnl
+AC_MSG_NOTICE([using LDFLAGS: $LDFLAGS])
+tst_bad_msg="oops, LDFLAGS should only specify linker flags, not"
+for word1 in $LDFLAGS; do
+  case "$word1" in
+    -D*)
+      AC_MSG_WARN([$tst_bad_msg macro definitions. Use CPPFLAGS for: $word1])
+      ;;
+    -U*)
+      AC_MSG_WARN([$tst_bad_msg macro suppressions. Use CPPFLAGS for: $word1])
+      ;;
+    -I*)
+      AC_MSG_WARN([$tst_bad_msg include directories. Use CPPFLAGS for: $word1])
+      ;;
+    -l* | --library=*)
+      AC_MSG_WARN([$tst_bad_msg libraries. Use LIBS for: $word1])
+      ;;
+  esac
+done
+
+dnl
+dnl CPPFLAGS should only specify C preprocessor flags
+dnl
+AC_MSG_NOTICE([using CPPFLAGS: $CPPFLAGS])
+tst_bad_msg="oops, CPPFLAGS should only specify C preprocessor flags, not"
+for word1 in $CPPFLAGS; do
+  case "$word1" in
+    -rpath*)
+      AC_MSG_WARN([$tst_bad_msg library runtime directories. Use LDFLAGS for: $word1])
+      ;;
+    -L* | --library-path=*)
+      AC_MSG_WARN([$tst_bad_msg library directories. Use LDFLAGS for: $word1])
+      ;;
+    -l* | --library=*)
+      AC_MSG_WARN([$tst_bad_msg libraries. Use LIBS for: $word1])
+      ;;
+  esac
+done
+
+dnl
+dnl CFLAGS should only specify C compiler flags
+dnl
+AC_MSG_NOTICE([using CFLAGS: $CFLAGS])
+tst_bad_msg="oops, CFLAGS should only specify C compiler flags, not"
+for word1 in $CFLAGS; do
+  case "$word1" in
+    -D*)
+      AC_MSG_WARN([$tst_bad_msg macro definitions. Use CPPFLAGS for: $word1])
+      ;;
+    -U*)
+      AC_MSG_WARN([$tst_bad_msg macro suppressions. Use CPPFLAGS for: $word1])
+      ;;
+    -I*)
+      AC_MSG_WARN([$tst_bad_msg include directories. Use CPPFLAGS for: $word1])
+      ;;
+    -rpath*)
+      AC_MSG_WARN([$tst_bad_msg library runtime directories. Use LDFLAGS for: $word1])
+      ;;
+    -L* | --library-path=*)
+      AC_MSG_WARN([$tst_bad_msg library directories. Use LDFLAGS for: $word1])
+      ;;
+    -l* | --library=*)
+      AC_MSG_WARN([$tst_bad_msg libraries. Use LIBS for: $word1])
+      ;;
+  esac
+done
+
 if test "x$want_curldebug_assumed" = "xyes" &&
   test "x$want_curldebug" = "xyes" && test "x$USE_ARES" = "x1"; then
   ac_configure_args="$ac_configure_args --enable-curldebug"