errno-list: prefer strerrorname_np() as errno_to_name() provider

TODO

@@ -1571,7 +1571,7 @@ Features:
 * add a new flag to chase() that stops chasing once the first missing
   component is found and then allows the caller to create the rest.
 
-* make use of new glibc 2.32 APIs sigabbrev_np() and strerrorname_np().
+* make use of new glibc 2.32 APIs sigabbrev_np().
 
 * if /usr/bin/swapoff fails due to OOM, log a friendly explanatory message about it
 

meson.build

@@ -675,6 +675,7 @@ foreach ident : [
         ['fsmount',           '''#include <sys/mount.h>'''],
         ['getdents64',        '''#include <dirent.h>'''],
         ['pidfd_spawn',       '''#include <spawn.h>'''],
+        ['strerrorname_np',   '''#include <string.h>'''],
 ]
 
         have = cc.has_function(ident[0], prefix : ident[1], args : '-D_GNU_SOURCE')

src/basic/errno-list.c

@@ -10,6 +10,8 @@ static const struct errno_name* lookup_errno(register const char *str,
                                              register GPERF_LEN_TYPE len);
 
 #include "errno-from-name.h"
+
+#if !HAVE_STRERRORNAME_NP
 #include "errno-to-name.h"
 
 const char* errno_to_name(int id) {
@@ -22,6 +24,7 @@ const char* errno_to_name(int id) {
 
         return errno_names[id];
 }
+#endif
 
 int errno_from_name(const char *name) {
         const struct errno_name *sc;

src/basic/errno-list.h

@@ -2,14 +2,28 @@
 #pragma once
 
 #include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
 /*
  * MAX_ERRNO is defined as 4095 in linux/err.h
  * We use the same value here.
  */
 #define ERRNO_MAX 4095
 
+#if HAVE_STRERRORNAME_NP
+static inline const char* errno_to_name(int id) {
+        if (id == 0) /* To stay in line with our own impl */
+                return NULL;
+
+        return strerrorname_np(abs(id));
+}
+#else
 const char* errno_to_name(int id);
+#endif
+
 int errno_from_name(const char *name);
+
 static inline bool errno_is_valid(int n) {
         return n > 0 && n <= ERRNO_MAX;
 }

src/test/test-errno-list.c

@@ -9,6 +9,9 @@
 #include "tests.h"
 
 TEST(errno_list) {
+        ASSERT_NULL(errno_names[0]);
+        ASSERT_NULL(errno_to_name(0));
+
         for (size_t i = 0; i < ELEMENTSOF(errno_names); i++) {
                 if (errno_names[i]) {
                         ASSERT_STREQ(errno_to_name(i), errno_names[i]);