Detect if __func__ can be used with debugging

CMakeLists.txt

@@ -481,6 +481,11 @@ if (HAVE_STRPTIME)
   check_c_source_runs("${STRPTIME_TEST_SOURCE}" STRPTIME_WORKS)
 endif ()
 
+try_compile(HAVE___FUNC__
+  ${CMAKE_CURRENT_BINARY_DIR}
+  ${CMAKE_CURRENT_SOURCE_DIR}/cmake/tests/test___func__.c
+)
+
 # TCP Fast Open.
 if (NOT ENABLE_TCP_FAST_OPEN)
   message(WARNING "TCP Fast Open disabled.")

cmake/include/cmakeconfig.h.in

@@ -213,6 +213,8 @@
 #cmakedefine HAVE_TARGET_ENDIANNESS
 #cmakedefine TARGET_IS_BIG_ENDIAN
 
+#cmakedefine HAVE___FUNC__		1
+
 #ifdef HAVE___FUNC__
 #define __FUNC__ __func__
 #else

cmake/tests/test___func__.c

@@ -0,0 +1,4 @@
+int main (int ac, char *av[])
+{
+	char *s = __func__;
+}