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Fix possible deadlock upon encoding-error' in open-input-string'.

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Partly addresses <http://bugs.gnu.org/11197>.

* libguile/strports.c (scm_mkstrport): Call `scm_port_non_buffer', set
  Z's cell type and stream, and release `scm_i_port_table_mutex' early.
  Reacquire `scm_i_port_table_mutex' once BUF, C_BUF, and STR_LEN are
  initialized.

* test-suite/tests/ports.test ("string ports")["encoding failure leads
  to exception"]: New test.
This commit is contained in:
Ludovic Courtès 2012-06-20 22:56:11 +02:00
parent ecb48dccba
commit 03fcf93bff
2 changed files with 39 additions and 7 deletions
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30
libguile/strports.c
View file

@ -288,7 +288,18 @@ scm_mkstrport (SCM pos, SCM str, long modes, const char *caller)
scm_i_dynwind_pthread_mutex_lock (&scm_i_port_table_mutex);
z = scm_new_port_table_entry (scm_tc16_strport);
pt = SCM_PTAB_ENTRY(z);
SCM_SET_CELL_TYPE (z, scm_tc16_strport);
pt = SCM_PTAB_ENTRY (z);
/* Make PT initially empty, and release the port-table mutex
immediately. This is so that if one of the function calls below
raises an exception, a pre-unwind catch handler can still create
new ports; for instance, `display-backtrace' needs to be able to
allocate a new string port. See <http://bugs.gnu.org/11197>. */
scm_port_non_buffer (pt);
SCM_SETSTREAM (z, SCM_UNPACK (scm_null_bytevector));
scm_dynwind_end ();
if (scm_is_false (str))
{
@ -296,10 +307,6 @@ scm_mkstrport (SCM pos, SCM str, long modes, const char *caller)
str_len = INITIAL_BUFFER_SIZE;
buf = scm_c_make_bytevector (str_len);
c_buf = (char *) SCM_BYTEVECTOR_CONTENTS (buf);
/* Reset `read_buf_size'. It will contain the actual number of
bytes written to PT. */
pt->read_buf_size = 0;
c_pos = 0;
}
else
@ -318,12 +325,21 @@ scm_mkstrport (SCM pos, SCM str, long modes, const char *caller)
free (copy);
c_pos = scm_to_unsigned_integer (pos, 0, str_len);
pt->read_buf_size = str_len;
}
/* Now, finish up the port. */
scm_i_pthread_mutex_lock (&scm_i_port_table_mutex);
SCM_SETSTREAM (z, SCM_UNPACK (buf));
SCM_SET_CELL_TYPE (z, scm_tc16_strport | modes);
if (scm_is_false (str))
/* Reset `read_buf_size'. It will contain the actual number of
bytes written to PT. */
pt->read_buf_size = 0;
else
pt->read_buf_size = str_len;
pt->write_buf = pt->read_buf = (unsigned char *) c_buf;
pt->read_pos = pt->write_pos = pt->read_buf + c_pos;
pt->write_buf_size = str_len;
@ -331,7 +347,7 @@ scm_mkstrport (SCM pos, SCM str, long modes, const char *caller)
pt->rw_random = 1;
scm_dynwind_end ();
scm_i_pthread_mutex_unlock (&scm_i_port_table_mutex);
/* Ensure WRITE_POS is writable. */
if ((modes & SCM_WRTNG) && pt->write_pos == pt->write_end)

16
test-suite/tests/ports.test
View file

@ -413,6 +413,22 @@
(pass-if "output check"
(string=? text result)))
(pass-if "encoding failure leads to exception"
;; Prior to 2.0.6, this would trigger a deadlock in `scm_mkstrport'.
;; See the discussion at <http://bugs.gnu.org/11197>, for details.
(catch 'encoding-error
(lambda ()
(with-fluids ((%default-port-encoding "ISO-8859-1"))
(let ((p (open-input-string "λ"))) ; raise an exception
#f)))
(lambda (key . rest)
#t)
(lambda (key . rest)
;; At this point, the port-table mutex used to be still held,
;; hence the deadlock. This situation would occur when trying
;; to print a backtrace, for instance.
(input-port? (open-input-string "foo")))))
(pass-if "%default-port-encoding is honored"
(let ((encodings '("UTF-8" "UTF-16" "ISO-8859-1" "ISO-8859-3")))
(equal? (map (lambda (e)