autoconf: Add some warning flags for clang 13 or newer

-Wnull-pointer-subtraction
-Wunused-but-set-parameter
-Wunused-but-set-variable

diff --git a/aclocal.m4 b/aclocal.m4
index ea69c095c1f5325e4b18cf6fe97685d6d04410ea..2df9fef6adcf74a65b1e84268f06b46cdd447118 100644 (file)
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -809,6 +809,7 @@ AC_DEFUN(AC_LBL_DEVEL,
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wcast-qual)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wmissing-prototypes)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wmissing-variable-declarations)
+                   AC_LBL_CHECK_COMPILER_OPT($1, -Wnull-pointer-subtraction)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wold-style-definition)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wpedantic)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wpointer-arith)
@@ -817,6 +818,8 @@ AC_DEFUN(AC_LBL_DEVEL,
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wsign-compare)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wstrict-prototypes)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wunreachable-code-return)
+                   AC_LBL_CHECK_COMPILER_OPT($1, -Wunused-but-set-parameter)
+                   AC_LBL_CHECK_COMPILER_OPT($1, -Wunused-but-set-variable)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wused-but-marked-unused)
                    AC_LBL_CHECK_COMPILER_OPT($1, -Wwrite-strings)
            fi