Allow strerror(0) and strerror_r(0, ...).

Of course, strerror_r() may still fail with ERANGE.

Although the POSIX specification said this could fail with EINVAL and
doing this likely indicates invalid use of errno, most other
implementations permitted it, various POSIX testsuites require it to
work (matching the older sys_errlist array) and apparently some
applications depend on it.

PR:		standards/151316
MFC after:	1 week

1 files changed, 13 insertions, 8 deletions

diff --git a/tools/regression/lib/libc/string/test-strerror.c b/tools/regression/lib/libc/string/test-strerror.c
index f5274ed..ffc1633 100644
--- a/tools/regression/lib/libc/string/test-strerror.c
+++ b/tools/regression/lib/libc/string/test-strerror.c
@@ -42,17 +42,12 @@ main(void)
 	char *sret;
 	int iret;
 
-	plan_tests(25);
+	plan_tests(27);
 
 	/*
 	 * strerror() failure tests.
 	 */
 	errno = 0;
-	sret = strerror(0);
-	ok1(strcmp(sret, "Unknown error: 0") == 0);
-	ok1(errno == EINVAL);
-
-	errno = 0;
 	sret = strerror(INT_MAX);
 	snprintf(buf, sizeof(buf), "Unknown error: %d", INT_MAX);
 	ok1(strcmp(sret, buf) == 0);
@@ -62,6 +57,11 @@ main(void)
 	 * strerror() success tests.
 	 */
 	errno = 0;
+	sret = strerror(0);
+	ok1(strcmp(sret, "No error: 0") == 0);
+	ok1(errno == 0);
+
+	errno = 0;
 	sret = strerror(EPERM);
 	ok1(strcmp(sret, "Operation not permitted") == 0);
 	ok1(errno == 0);
@@ -79,8 +79,8 @@ main(void)
 	 * strerror_r() failure tests.
 	 */
 	memset(buf, '*', sizeof(buf));
-	iret = strerror_r(0, buf, sizeof(buf));
-	ok1(strcmp(buf, "Unknown error: 0") == 0);
+	iret = strerror_r(-1, buf, sizeof(buf));
+	ok1(strcmp(buf, "Unknown error: -1") == 0);
 	ok1(iret == EINVAL);
 
 	memset(buf, '*', sizeof(buf));
@@ -117,6 +117,11 @@ main(void)
 	 * strerror_r() success tests.
 	 */
 	memset(buf, '*', sizeof(buf));
+	iret = strerror_r(0, buf, sizeof(buf));
+	ok1(strcmp(buf, "No error: 0") == 0);
+	ok1(iret == 0);
+
+	memset(buf, '*', sizeof(buf));
 	iret = strerror_r(EDEADLK, buf, sizeof(buf));
 	ok1(strcmp(buf, "Resource deadlock avoided") == 0);
 	ok1(iret == 0);