linux-kernel - [PATCH v3 05/12] tools/nolibc: implement %m if errno is not defined

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Message-ID: <20250924142059.527768-6-benjamin@sipsolutions.net>
Date: Wed, 24 Sep 2025 16:20:52 +0200
From: Benjamin Berg <benjamin@...solutions.net>
To: linux-um@...ts.infradead.org,
	Willy Tarreau <w@....eu>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	linux-kselftest@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	Benjamin Berg <benjamin.berg@...el.com>
Subject: [PATCH v3 05/12] tools/nolibc: implement %m if errno is not defined

From: Benjamin Berg <benjamin.berg@...el.com>

For improved compatibility, print %m as "unknown error" when nolibc is
compiled using NOLIBC_IGNORE_ERRNO.

Signed-off-by: Benjamin Berg <benjamin.berg@...el.com>
---
 tools/include/nolibc/stdio.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
index 724d05ce6962..1f16dab2ac88 100644
--- a/tools/include/nolibc/stdio.h
+++ b/tools/include/nolibc/stdio.h
@@ -321,11 +321,13 @@ int __nolibc_printf(__nolibc_printf_cb cb, intptr_t state, size_t n, const char
 				if (!outstr)
 					outstr="(null)";
 			}
-#ifndef NOLIBC_IGNORE_ERRNO
 			else if (c == 'm') {
+#ifdef NOLIBC_IGNORE_ERRNO
+				outstr = "unknown error";
+#else
 				outstr = strerror(errno);
-			}
 #endif /* NOLIBC_IGNORE_ERRNO */
+			}
 			else if (c == '%') {
 				/* queue it verbatim */
 				continue;
-- 
2.51.0