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authorAlexandre Oliva <aoliva@redhat.com>2014-11-21 02:06:22 -0200
committerAlexandre Oliva <aoliva@redhat.com>2014-11-21 02:16:02 -0200
commit7729e0e91afbf8d45bb322d7e2d53f417fab01ed (patch)
treeb081908ff729dc647b179cb425fbe721e857cbe8
parenta4ea5e2809a20521e4300725d5062768883ffc50 (diff)
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ctermid: return string literal, document MT-Safety pitfall
for ChangeLog * 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.
-rw-r--r--ChangeLog8
-rw-r--r--manual/job.texi8
-rw-r--r--sysdeps/posix/ctermid.c16
3 files changed, 21 insertions, 11 deletions
diff --git a/ChangeLog b/ChangeLog
index d57c023ac1..96aafaeda0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
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
of not passing it a buffer.
Reported by Peng Haitao.
diff --git a/manual/job.texi b/manual/job.texi
index 4f9bd81ffe..095c26d930 100644
--- a/manual/job.texi
+++ b/manual/job.texi
@@ -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
diff --git a/sysdeps/posix/ctermid.c b/sysdeps/posix/ctermid.c
index 0ef9a3fe23..9714285224 100644
--- a/sysdeps/posix/ctermid.c
+++ b/sysdeps/posix/ctermid.c
@@ -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);
}