add new header for x_assert() macro

libs/pbd/pbd/assert.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2022 Paul Davis <paul@linuxaudiosystems.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef __libpbd_assert_h__
+#define __libpbd_assert_h__
+
+/*  macro designed to handle cases like this:
+
+     int foo = some_method ();
+     assert (foo == 0);
+
+   In an optimized build, this will generate warnings about foo being unused,
+   and so remove that clutter, use:
+
+     x_assert (foo, foo == 0);
+*/
+
+#define x_assert(VAR, EXPR)  \
+# ifndef NDEBUG              \
+assert (EXPR);               \
+# else                       \
+(void) (VAR)                 \
+# endif
+
+#endif /* __libpbd_assert_h__ */