compat/glib: work around glib bug that causes a compilation error in …

…clang++

Signed-off-by: Balazs Scheidler <balazs.scheidler@axoflow.com>

configure.ac

@@ -480,14 +480,6 @@ dnl C++
 # Ok, here is the deal
 # clang cannot compile the current source, it has nultiple issues
 # replace it till not fixed them
-if test "x$CXX" = "xclang"; then
-        AC_MSG_ERROR(["clang cannot compile syslog-ng C++ sources, try using gcc instead (export CXX=gcc) for C++ compilation (NOTE: on macOS you need Homebrew gcc not the Apple one)"])
-elif test "x$CC" = "xclang"; then
-        CPP_COMPILER="gcc"
-        AC_MSG_WARN(["clang cannot compile syslog-ng C++ sources, switched to $CPP_COMPILER for C++ compilation (NOTE: on macOS you need Homebrew gcc not the Apple one)"])
-else
-        CPP_COMPILER="$CXX $CC"
-fi
 # This one is useful for checking the available compilers
 # AC_MSG_RESULT(gcc = $(which gcc) - g++ = $(which g++) - clang = $(which clang))
 # AC_MSG_RESULT(Paths: gcc = $(ls -Al $(which gcc)) - g++ = $(ls -Al $(which g++)) - clang = $(ls -Al $(which clang)))

lib/compat/glib.h

@@ -59,4 +59,36 @@ gboolean slng_g_hash_table_insert (GHashTable *hash_table, gpointer key, gpointe
 gunichar g_utf8_get_char_validated_fixed (const gchar *p, gssize max_len);
 #endif
 
+#if defined(__clang__) && defined(g_atomic_pointer_compare_and_exchange) && defined(__ATOMIC_SEQ_CST) && defined(G_ATOMIC_LOCK_FREE) && defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
+
+/* workaround clang++ compilation error */
+
+#if !(defined(glib_typeof) && defined(G_CXX_STD_VERSION))
+#undef g_atomic_pointer_compare_and_exchange
+
+/* the difference here vs glib is the extra (void **) casts in atomic and
+ * newval, which triggered a compilation warning in clang++:
+ *
+ *
+ *   .../lib/atomic-gssize.h:118:10: error: cannot initialize a parameter of type 'gssize *' (aka 'long *') with an rvalue of type 'void *'
+ *     return g_atomic_pointer_compare_and_exchange(&a->value, oldval, newval);
+ *            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *   /usr/include/glib-2.0/glib/gatomic.h:258:44: note: expanded from macro 'g_atomic_pointer_compare_and_exchange'
+ *       __atomic_compare_exchange_n ((atomic), (void *) (&(gapcae_oldval)), (newval), FALSE, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ? TRUE : FALSE; \
+ *                                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ */
+
+#define g_atomic_pointer_compare_and_exchange(atomic, oldval, newval) \
+  (G_GNUC_EXTENSION ({                                                       \
+    G_STATIC_ASSERT (sizeof (oldval) == sizeof (gpointer));                  \
+    gpointer gapcae_oldval = (gpointer)(oldval);                             \
+    G_STATIC_ASSERT (sizeof *(atomic) == sizeof (gpointer));                 \
+    (void) (0 ? (gpointer) *(atomic) : NULL);                                \
+    __atomic_compare_exchange_n ((void **) (atomic), (&(gapcae_oldval)), (void **) (newval), FALSE, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ? TRUE : FALSE; \
+  }))
+#endif
+
+#endif
+
 #endif