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ctermid: return string literal, document MT-Safety pitfall

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	* sysdeps/posix/ctermid.c (ctermid): Return a pointer to a
	string literal if not passed a buffer.
	* manual/job.texi (ctermid): Update reasoning, note deviation
	from posix, suggest mtasurace when not passed a buffer, for
	future non-preliminary safety notes.
This commit is contained in:
Alexandre Oliva 2014-11-21 02:06:22 -02:00
parent a4ea5e2809
commit 7729e0e91a
3 changed files with 21 additions and 11 deletions
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8
ChangeLog
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@ -1,3 +1,11 @@
2014-11-21 Alexandre Oliva <aoliva@redhat.com>
* sysdeps/posix/ctermid.c (ctermid): Return a pointer to a
string literal if not passed a buffer.
* manual/job.texi (ctermid): Update reasoning, note deviation
from posix, suggest mtasurace when not passed a buffer, for
future non-preliminary safety notes.
2014-11-21 Alexandre Oliva <aoliva@redhat.com>
* manual/users.texi (cuserid): Fix MT-Safety note for the case

8
manual/job.texi
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@ -1039,10 +1039,12 @@ The function @code{ctermid} is declared in the header file
@comment stdio.h
@comment POSIX.1
@deftypefun {char *} ctermid (char *@var{string})
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@safety{@prelim{}@mtsafe{@mtsposix{/!string}}@assafe{}@acsafe{}}
@c This function is a stub by default; the actual implementation, for
@c posix systems, returns an internal buffer if passed a NULL string,
@c but the internal buffer is always set to /dev/tty.
@c posix systems, returns a pointer to a string literal if passed a NULL
@c string. It's not clear we want to commit to being MT-Safe in the
@c !string case, so maybe add mtasurace{:ctermid/!string} when we take
@c prelim out, to make room for using a static buffer in the future.
The @code{ctermid} function returns a string containing the file name of
the controlling terminal for the current process. If @var{string} is
not a null pointer, it should be an array that can hold at least

16
sysdeps/posix/ctermid.c
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@ -19,17 +19,17 @@
#include <string.h>
/* Return the name of the controlling terminal.
If S is not NULL, the name is copied into it (it should be at
least L_ctermid bytes long), otherwise a static buffer is used. */
/* Return the name of the controlling terminal. If S is not NULL, the
name is copied into it (it should be at least L_ctermid bytes
long), otherwise we return a pointer to a non-const but read-only
string literal, that POSIX states the caller must not modify. */
char *
ctermid (s)
char *s;
ctermid (char *s)
{
static char name[L_ctermid];
char *name = (char /*drop const*/ *) "/dev/tty";
if (s == NULL)
s = name;
return name;
return strcpy (s, "/dev/tty");
return strcpy (s, name);
}