Add assert() for debug assertions

assert() is like BUG_ON() but compiles to nothing unless DEBUG is defined.
This is useful when a condition is an error but a board reset is unlikely
to fix it, so it is better to soldier on in hope. Assertion failures should
be caught during development/test.

It turns out that assert() is defined separately in a few places in U-Boot
with various meanings. This patch cleans up some of these.

Build errors exposed by this change (and defining DEBUG) are also fixed in
this patch.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/common.h

@@ -124,6 +124,27 @@ typedef volatile unsigned char	vu_char;
 #define debugX(level,fmt,args...)
 #endif	/* DEBUG */
 
+#ifdef DEBUG
+# define _DEBUG 1
+#else
+# define _DEBUG 0
+#endif
+
+/*
+ * An assertion is run-time check done in debug mode only. If DEBUG is not
+ * defined then it is skipped. If DEBUG is defined and the assertion fails,
+ * then it calls panic*( which may or may not reset/halt U-Boot (see
+ * CONFIG_PANIC_HANG), It is hoped that all failing assertions are found
+ * before release, and after release it is hoped that they don't matter. But
+ * in any case these failing assertions cannot be fixed with a reset (which
+ * may just do the same assertion again).
+ */
+void __assert_fail(const char *assertion, const char *file, unsigned line,
+		   const char *function);
+#define assert(x) \
+	({ if (!(x) && _DEBUG) \
+		__assert_fail(#x, __FILE__, __LINE__, __func__); })
+
 #define error(fmt, args...) do {					\
 		printf("ERROR: " fmt "\nat %s:%d/%s()\n",		\
 			##args, __FILE__, __LINE__, __func__);		\