From: Tobias Stoeckmann <tobias@stoeckmann.org>
Subject: Re: wprintf(3): Fix errno value and document it
To: tech@openbsd.org
Date: Fri, 16 May 2025 22:48:01 +0200

On Fri, May 16, 2025 at 10:42:59PM +0200, Tobias Stoeckmann wrote:
> https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdio/vfprintf.c#rev1.73

Of course the correct patch has to take both code places into account:

Index: vfwprintf.c
===================================================================
RCS file: /cvs/src/lib/libc/stdio/vfwprintf.c,v
diff -u -p -u -p -r1.23 vfwprintf.c
--- vfwprintf.c	6 Oct 2023 16:41:02 -0000	1.23
+++ vfwprintf.c	16 May 2025 20:46:16 -0000
@@ -1059,7 +1059,7 @@ error:
 	goto finish;
 
 overflow:
-	errno = ENOMEM;
+	errno = EOVERFLOW;
 	ret = -1;
 
 finish:
@@ -1450,7 +1450,7 @@ done:
 	goto finish;
 
 overflow:
-	errno = ENOMEM;
+	errno = EOVERFLOW;
 	ret = -1;
 
 finish:
Index: wprintf.3
===================================================================
RCS file: /cvs/src/lib/libc/stdio/wprintf.3,v
diff -u -p -u -p -r1.10 wprintf.3
--- wprintf.3	31 Mar 2022 17:27:16 -0000	1.10
+++ wprintf.3	16 May 2025 20:46:16 -0000
@@ -584,6 +584,21 @@ In no case does a non-existent or small 
 a numeric field; if the result of a conversion is wider than the field
 width, the
 field is expanded to contain the conversion result.
+.Sh ERRORS
+In addition to the errors documented for the
+.Xr write 2
+system call, the
+.Fn wprintf
+family of functions may fail if:
+.Bl -tag -width Er
+.It Bq Er EILSEQ
+An invalid wide character code was encountered.
+.It Bq Er ENOMEM
+Insufficient storage space is available.
+.It Bq Er EOVERFLOW
+The return value would be too large to be represented by an
+.Vt int .
+.El
 .Sh SEE ALSO
 .Xr btowc 3 ,
 .Xr fputws 3 ,