On OpenBSD 7.8, gl_cv_func_printf_enomem is defined to "no". This case
wasn't documented previously, but we can see the cause using this diff:
diff --git a/m4/printf.m4 b/m4/printf.m4
index 0de493b690..1221de172f 100644
--- a/m4/printf.m4
+++ b/m4/printf.m4
@@ -1547,6 +1547,8 @@ AC_DEFUN([gl_PRINTF_ENOMEM]
return 77;
#endif
ret = printf ("%.500f", 1.0);
+ printf ("%s\n", strerror (errno));
+ printf ("%d\n", ret);
return !(ret == 502 || (ret < 0 && errno == ENOMEM));
}
]])])
It reveals that printf returns zero despite errno being set to ENOMEM
and nothing being printed.
Our autoconf tests already caught this, but here is a patch documenting
it.
Collin
>From f1aae65e7aaaf88ae77766ac2be140ae6fc017c9 Mon Sep 17 00:00:00 2001
Message-ID:
From: Collin Funk
Date: Mon, 19 Jan 2026 12:45:07 -0800
Subject: [PATCH] doc: mention an OpenBSD printf bug.
* doc/posix-functions/printf.texi: Mention that OpenBSD does not return
a negative number after running out of memory.
---
ChangeLog | 6 ++
doc/posix-functions/printf.texi | 4
2 files changed, 10 insertions(+)
diff --git a/ChangeLog b/ChangeLog
index b96ea8fcf3..eac539ae34 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2026-01-19 Collin Funk
+
+ doc: mention an OpenBSD printf bug.
+ * doc/posix-functions/printf.texi: Mention that OpenBSD does not return
+ a negative number after running out of memory.
+
2026-01-19 Paul Eggert
xalloc: tweak for GCC 4.6, possible inlining bugs
diff --git a/doc/posix-functions/printf.texi b/doc/posix-functions/printf.texi
index 8b33702a83..a67e3c5e8f 100644
--- a/doc/posix-functions/printf.texi
+++ b/doc/posix-functions/printf.texi
@@ -111,6 +111,10 @@ @node printf
@item
This function can crash in out-of-memory conditions on some platforms:
FreeBSD 14.0, NetBSD 5.0.
+@item
+This function returns zero instead of a negative number after running
+out of memory:
+OpenBSD 7.8.
@end itemize
Portability problems fixed by Gnulib module @code{printf-gnu}:
--
2.52.0
