Only provide function information in compile environments that support

the C99 variable __func__ and never for C++.  Provide a more meaningful
example in the assert(3) manual.

Reviewed by:	asmodai, bde

lib/libc/gen/assert.c

@@ -45,14 +45,19 @@ __FBSDID("$FreeBSD$");
 #include <stdlib.h>
 
 void
-__assert(function, file, line, failedexpr)
-	const char *function, *file;
+__assert(func, file, line, failedexpr)
+	const char *func, *file;
 	int line;
 	const char *failedexpr;
 {
-	(void)fprintf(stderr,
-		      "assertion (%s) failed: function %s(), file %s:%d\n",
-		      failedexpr, function, file, line);
+	if (func == NULL)
+		(void)fprintf(stderr,
+		     "assertion (%s) failed: file %s:%d\n", failedexpr,
+		     file, line);
+	else
+		(void)fprintf(stderr,
+		     "assertion (%s) failed: function %s(), file %s:%d\n",
+		     failedexpr, func, file, line);
 	abort();
 	/* NOTREACHED */
 }

lib/libstand/assert.c

@@ -32,10 +32,13 @@ __FBSDID("$FreeBSD$");
 #include "stand.h"
 
 void
-__assert(const char *function, const char *file, int line,
-	 const char *expression)
+__assert(const char *func, const char *file, int line, const char *expression)
 {
-	printf("assertion (%s) failed: function %s(), file %s:%d\n",
-	       expression, function, file, line);
+	if (func == NULL)
+		printf("assertion (%s) failed: file %s:%d\n", expression,
+		    file, line);
+	else
+		printf("assertion (%s) failed: function %s(), file %s:%d\n",
+		    expression, func, file, line);
 	exit();
 }

share/man/man3/assert.3

@@ -72,22 +72,22 @@ as a macro
 .Xr cc 1
 option
 .Fl D Ns Dv NDEBUG ) .
-.Sh DIAGNOSTICS
-The following diagnostic message is written to
-.Em stderr
-if
-.Ar expression
-is false:
+.Sh EXAMPLES
+The assertion:
 .Bd -literal -offset indent
-"assertion (%s) failed: function %s(), file %s:%d\en", \e
-		    "expression", __func__, __FILE__, __LINE__);
+assert(1 == 0);
+.Ed
+.Pp
+generates a diagnostic message similar to the following:
+.Bd -literal -offset indent
+assertion (1 == 0) failed: function main(), file assertion.c:100
 .Ed
 .Sh SEE ALSO
 .Xr abort 3
 .Sh STANDARDS
 The
 .Fn assert
-macro confirms to
+macro conforms to
 .St -isoC-99 .
 .Sh HISTORY
 An

sys/sys/cdefs.h

@@ -48,6 +48,11 @@
 #define	__END_DECLS
 #endif
 
+/* XXX: should have __STDC_VERSION__ < 199901 */
+#if !defined(__GNUC__) || defined(__cplusplus)
+#define	__func__	NULL
+#endif
+
 /*
  * The __CONCAT macro is used to concatenate parts of symbol names, e.g.
  * with "#define OLD(foo) __CONCAT(old,foo)", OLD(foo) produces oldfoo.