[PATCH v2 2/2] stpncpy.3, string.3, string_copying.7: Clarify that st[rp]ncpy() pad with null bytes

Alejandro Colomar
2023-11-09T15:20:45Z

The previous wording could be interpreted as if the nulls were already
in place. Clarify that it's this function which pads with null bytes.

Also, it copies "characters" from the src string. That's a bit more
specific than copying "bytes", and makes it clearer that the terminating
null byte in src is not part of the copy.

Suggested-by: Jonny Grant <jg@jguk.org>
Cc: DJ Delorie <dj@redhat.com>
Cc: Jonny Grant <jg@jguk.org>
Cc: Matthew House <mattlloydhouse@gmail.com>
Cc: Oskari Pirhonen <xxc3ncoredxx@gmail.com>
Cc: Thorsten Kukuk <kukuk@suse.com>
Cc: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: Zack Weinberg <zack@owlfolio.org>
Cc: "G. Branden Robinson" <g.branden.robinson@gmail.com>
Cc: Carlos O'Donell <carlos@redhat.com>
Cc: Paul Eggert <eggert@cs.ucla.edu>
Cc: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
---
man3/stpncpy.3 | 10 ++++++----
man3/string.3 | 11 ++---------
man7/string_copying.7 | 3 ++-
3 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/man3/stpncpy.3 b/man3/stpncpy.3
index f86ff8c29..3cf4eb371 100644
--- a/man3/stpncpy.3
+++ b/man3/stpncpy.3
@@ -7,7 +7,8 @@
.SH NAME
stpncpy, strncpy
\-
-fill a fixed-width null-padded buffer with bytes from a string
+fill a fixed-width buffer with characters from a string
+and pad with null bytes
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
@@ -36,10 +37,11 @@ .SH SYNOPSIS
_GNU_SOURCE
.fi
.SH DESCRIPTION
-These functions copy bytes from the string pointed to by
+These functions copy characters from the string pointed to by
.I src
-into a null-padded character sequence at the fixed-width buffer pointed to by
-.IR dst .
+into a character sequence at the fixed-width buffer pointed to by
+.IR dst ,
+and pad with null bytes.
If the destination buffer,
limited by its size,
isn't large enough to hold the copy,
diff --git a/man3/string.3 b/man3/string.3
index aba5efd2b..bd8b342a6 100644
--- a/man3/string.3
+++ b/man3/string.3
@@ -179,21 +179,14 @@ .SH SYNOPSIS
.I n
bytes to
.IR dest .
-.SS Obsolete functions
.TP
.nf
.BI "char *strncpy(char " dest "[restrict ." n "], \
const char " src "[restrict ." n ],
.BI " size_t " n );
.fi
-Copy at most
-.I n
-bytes from string
-.I src
-to
-.IR dest ,
-returning a pointer to the start of
-.IR dest .
+Fill a fixed‐width buffer with characters from a string
+and pad with null bytes.
.SH DESCRIPTION
The string functions perform operations on null-terminated
strings.
diff --git a/man7/string_copying.7 b/man7/string_copying.7
index 0e179ba34..865271c6f 100644
--- a/man7/string_copying.7
+++ b/man7/string_copying.7
@@ -41,7 +41,8 @@ .SS Strings
.\" ----- SYNOPSIS :: Null-padded character sequences --------/
.SS Null-padded character sequences
.nf
-// Fill a fixed-width null-padded buffer with bytes from a string.
+// Fill a fixed-width buffer with characters from a string
+// and pad with null bytes.
.BI "char *strncpy(char " dst "[restrict ." sz "], \
const char *restrict " src ,
.BI " size_t " sz );
--
2.42.0