From e0e96d263039a5cf0e085a361eccf426db2f9d21 Mon Sep 17 00:00:00 2001
From: Alejandro Colomar <alx@kernel.org>
Date: Fri, 15 Dec 2023 14:52:58 +0100
Subject: string_copying.7: stpecpy(), strtcpy(): Set errno on failure

Signed-off-by: Alejandro Colomar <alx@kernel.org>
---
 man7/string_copying.7 | 40 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/man7/string_copying.7 b/man7/string_copying.7
index 02e379a7d..cc8904493 100644
--- a/man7/string_copying.7
+++ b/man7/string_copying.7
@@ -505,6 +505,29 @@ The
 .I dst
 pointer,
 which is useless.
+.\" ----- ERRORS ------------------------------------------------------/
+.SH ERRORS
+Most of these functions don't set
+.IR errno .
+.TP
+.BR stpecpy ()
+.RS
+.TP
+.B E2BIG
+The string has been truncated.
+.RE
+.TP
+.BR strtcpy ()
+.RS
+.TP
+.B ENOBUFS
+.I dsize
+was
+.BR 0 .
+.TP
+.B E2BIG
+The string has been truncated.
+.RE
 .\" ----- NOTES :: strscpy(9) -----------------------------------------/
 .SH NOTES
 The Linux kernel has an internal function for copying strings,
@@ -513,7 +536,9 @@ which is identical to
 .BR strtcpy (),
 except that it returns
 .B \-E2BIG
-instead of \-1.
+instead of \-1
+and it doesn't set
+.IR errno .
 .\" ----- CAVEATS :: --------------------------------------------------/
 .SH CAVEATS
 Don't mix chain calls to truncating and non-truncating functions.
@@ -704,6 +729,7 @@ char *
 .IR stpecpy "(char *dst, char end[0], const char *restrict src)"
 {
     bool    trunc;
+    char    *p;
     size_t  dsize, dlen, slen;
 \&
     if (dst == end)
@@ -716,7 +742,10 @@ char *
     trunc = (slen == dsize);
     dlen = slen \- trunc;
 \&
-    return stpcpy(mempcpy(dst, src, dlen), "") + trunc;
+    p = stpcpy(mempcpy(dst, src, dlen), "");
+    if (trunc)
+        errno = E2BIG;
+    return p + trunc;
 }
 \&
 .\" ----- EXAMPLES :: Implementations :: strtcpy() --------------------/
@@ -726,15 +755,18 @@ ssize_t
     bool    trunc;
     size_t  dlen, slen;
 \&
-    if (dsize == 0)
+    if (dsize == 0) {
+        errno = ENOBUFS;
         return \-1;
+    }
 \&
     slen = strnlen(src, dsize);
     trunc = (slen == dsize);
     dlen = slen \- trunc;
 \&
     stpcpy(mempcpy(dst, src, dlen), "");
-
+    if (trunc)
+        errno = E2BIG;
     return trunc ? \-1 : slen;
 }
 .\" ----- SEE ALSO :: -------------------------------------------------/
-- 
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