git: 3131e7a41725 - stable/14 - csu: C standard requires errno on main() entry

[Konstantin Belousov]

The branch stable/14 has been updated by kib:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=3131e7a41725acd53d7612da8cb9de278f81e244

commit 3131e7a41725acd53d7612da8cb9de278f81e244
Author:     Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2025-06-23 23:46:43 +0000
Commit:     Konstantin Belousov <k...@freebsd.org>
CommitDate: 2025-06-29 00:29:12 +0000

    csu: C standard requires errno on main() entry
    
    (cherry picked from commit 64584008139f73b07fa7c7979c41780be458b8cc)
---
 lib/libc/csu/libc_start1.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lib/libc/csu/libc_start1.c b/lib/libc/csu/libc_start1.c
index f0e708e405ce..a1887a2c28c0 100644
--- a/lib/libc/csu/libc_start1.c
+++ b/lib/libc/csu/libc_start1.c
@@ -28,6 +28,7 @@
 #include <sys/param.h>
 #include <sys/elf.h>
 #include <sys/elf_common.h>
+#include <errno.h>
 #include <stdlib.h>
 #include "libc_private.h"
 
@@ -154,6 +155,13 @@ __libc_start1(int argc, char *argv[], char *env[], void 
(*cleanup)(void),
        }
 
        handle_static_init(argc, argv, env);
+
+       /*
+        * C17 4.3 paragraph 3:
+        * The value of errno in the initial thread is zero at program
+        * startup.
+        */
+       errno = 0;
        exit(mainX(argc, argv, env));
 }
 
@@ -182,5 +190,6 @@ __libc_start1_gcrt(int argc, char *argv[], char *env[],
        monstartup(eprolp, etextp);
 
        handle_static_init(argc, argv, env);
+       errno = 0;
        exit(mainX(argc, argv, env));
 }