6a576391d6
There's no standard function that copies from a null-padded character sequence into a string. A few standard functions can be workarounded to do that: - strncat(3): This function is designed to catenate from a null-padded character sequence into a string. The catch is that there's no *cpy() equivalent of it --strncpy(3) is not at all related to strncat(3); don't be fooled by the confusing name--, so one would need to zero the first byte before the call to strncat(3). It also has the inconvenient that it returns a useless value. - strncpy(3): This function is designed to copy from a string to a null-padded character sequence; the opposite of what we want to do. If one passes the size of src instead of the size of dst, and then manually zeroes the last byte of the dst buffer, something similar to what we want happens. However, this does more than what we want: it also padds with NUL the remaining bytes after the terminating NUL. That extra work can confuse maintainers to believe that it's necessary. That is exactly what happens in logout.c. src/logoutd.c-46- /* src/logoutd.c-47- * ut_user may not have the terminating NUL. src/logoutd.c-48- */ src/logoutd.c:49: strncpy (user, ut->ut_user, sizeof (ut->ut_user)); src/logoutd.c-50- user[sizeof (ut->ut_user)] = '\0'; In that logout.c case --and in most invocations of strncpy(3), which is usually a wrong tool-- the extra work is not wanted, so it's preferrable to use the right tool, a function that does exactly what's needed and nothing more than that. That tool is zustr2stp(). Read string_copying(7) for a more complete comparison of string copying functions. Cc: Christian Göttsche <cgzones@googlemail.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Iker Pedrosa <ipedrosa@redhat.com> Signed-off-by: Alejandro Colomar <alx@kernel.org>
18 lines
297 B
C
18 lines
297 B
C
/*
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* SPDX-FileCopyrightText: 2022-2023, Alejandro Colomar <alx@kernel.org>
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <config.h>
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#include <stddef.h>
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#ident "$Id$"
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#include "zustr2stp.h"
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extern inline char *zustr2stp(char *restrict dst, const char *restrict src,
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size_t sz);
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