string: Add strerrorname_np and strerrordesc_np

The strerrorname_np returns error number name (e.g. "EINVAL" for EINVAL)
while strerrordesc_np returns string describing error number (e.g
"Invalid argument" for EINVAL).  Different than strerror,
strerrordesc_np does not attempt to translate the return description,
both functions return NULL for an invalid error number.

They should be used instead of sys_errlist and sys_nerr, both are
thread and async-signal safe.  These functions are GNU extensions.

Checked on x86-64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
and s390x-linux-gnu.

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

2 files changed, 98 insertions, 0 deletions

diff --git a/stdio-common/errlist.c b/stdio-common/errlist.c
index df52356066..d15f13a22a 100644
--- a/stdio-common/errlist.c
+++ b/stdio-common/errlist.c
@@ -35,4 +35,37 @@ __get_errlist (int errnum)
   return NULL;
 }
 
+static const union sys_errname_t
+{
+  struct
+  {
+#define MSGSTRFIELD1(line) str##line
+#define MSGSTRFIELD(line)  MSGSTRFIELD1(line)
+#define _S(n, str)         char MSGSTRFIELD(__LINE__)[sizeof(str)];
+#include <errlist.h>
+#undef _S
+  };
+  char str[0];
+} _sys_errname = { {
+#define _S(n, s) s,
+#include <errlist.h>
+#undef _S
+} };
+
+static const unsigned short _sys_errnameidx[] =
+{
+#define _S(n, s) [n] = offsetof(union sys_errname_t, MSGSTRFIELD(__LINE__)),
+#include <errlist.h>
+#undef _S
+};
+
+const char *
+__get_errname (int errnum)
+{
+  if (errnum < 0 || errnum >= array_length (_sys_errnameidx)
+      || (errnum > 0 && _sys_errnameidx[errnum] == 0))
+    return NULL;
+  return _sys_errname.str + _sys_errnameidx[errnum];
+}
+
 #include <errlist-compat.c>
diff --git a/stdio-common/test-strerr.c b/stdio-common/test-strerr.c
new file mode 100644
index 0000000000..fded208118
--- /dev/null
+++ b/stdio-common/test-strerr.c
@@ -0,0 +1,65 @@
+/* Test strerrorname_np and strerrordesc_np.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+#include <errno.h>
+#include <array_length.h>
+
+#include <support/support.h>
+#include <support/check.h>
+
+#define N_(name)      name
+
+static const char *const errlist[] =
+  {
+/* This file is auto-generated from errlist.def.  */
+#include <errlist.h>
+  };
+
+#define MSGSTR_T errname_t
+#define MSGSTR   errname
+#define MSGIDX   errnameidx
+#include <errlist-name.h>
+#undef MSGSTR
+#undef MSGIDX
+
+static int
+do_test (void)
+{
+  TEST_VERIFY (strerrordesc_np (-1) == NULL);
+  TEST_VERIFY (strerrordesc_np (array_length (errlist)) == NULL);
+  for (size_t i = 0; i < array_length (errlist); i++)
+    {
+      if (errlist[i] == NULL)
+        continue;
+      TEST_COMPARE_STRING (strerrordesc_np (i), errlist[i]);
+    }
+
+  TEST_VERIFY (strerrorname_np (-1) == NULL);
+  TEST_VERIFY (strerrorname_np (array_length (errlist)) == NULL);
+  for (size_t i = 0; i < array_length (errlist); i++)
+    {
+      if (errlist[i] == NULL)
+        continue;
+      TEST_COMPARE_STRING (strerrorname_np (i), errname.str + errnameidx[i]);
+    }
+
+  return 0;
+}
+
+#include <support/test-driver.c>