Mailing List Archive

Update of /cvsroot/python/python/dist/src/Objects
In directory sc8-pr-cvs1:/tmp/cvs-serv643/Objects

Modified Files:
fileobject.c
Log Message:
Fixed bug

[#521782] unreliable file.read() error handling

* Objects/fileobject.c
(file_read): Clear errors before leaving the loop in all situations,
and also check if some data was read before exiting the loop with an
EWOULDBLOCK exception.

* Doc/lib/libstdtypes.tex
* Objects/fileobject.c
Document that sometimes a read() operation can return less data than
what the user asked, if running in non-blocking mode.

* Misc/NEWS
Document the fix.


Index: fileobject.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Objects/fileobject.c,v
retrieving revision 2.171
retrieving revision 2.172
diff -C2 -d -r2.171 -r2.172
*** fileobject.c 11 Dec 2002 13:06:53 -0000 2.171
--- fileobject.c 16 Dec 2002 18:12:53 -0000 2.172
***************
*** 742,745 ****
--- 742,759 ----
}

+ #if defined(EWOULDBLOCK) && defined(EAGAIN) && EWOULDBLOCK != EAGAIN
+ #define BLOCKED_ERRNO(x) ((x) == EWOULDBLOCK || (x) == EAGAIN)
+ #else
+ #ifdef EWOULDBLOCK
+ #define BLOCKED_ERRNO(x) ((x) == EWOULDBLOCK)
+ #else
+ #ifdef EAGAIN
+ #define BLOCKED_ERRNO(x) ((x) == EAGAIN)
+ #else
+ #define BLOCKED_ERRNO(x) 0
+ #endif
+ #endif
+ #endif
+
static PyObject *
file_read(PyFileObject *f, PyObject *args)
***************
*** 775,790 ****
if (!ferror(f->f_fp))
break;
- PyErr_SetFromErrno(PyExc_IOError);
clearerr(f->f_fp);
Py_DECREF(v);
return NULL;
}
bytesread += chunksize;
! if (bytesread < buffersize)
break;
if (bytesrequested < 0) {
buffersize = new_buffersize(f, buffersize);
if (_PyString_Resize(&v, buffersize) < 0)
return NULL;
}
}
--- 789,815 ----
if (!ferror(f->f_fp))
break;
clearerr(f->f_fp);
+ /* When in non-blocking mode, data shouldn't
+ * be discarded if a blocking signal was
+ * received. That will also happen if
+ * chunksize != 0, but bytesread < buffersize. */
+ if (bytesread > 0 && BLOCKED_ERRNO(errno))
+ break;
+ PyErr_SetFromErrno(PyExc_IOError);
Py_DECREF(v);
return NULL;
}
bytesread += chunksize;
! if (bytesread < buffersize) {
! clearerr(f->f_fp);
break;
+ }
if (bytesrequested < 0) {
buffersize = new_buffersize(f, buffersize);
if (_PyString_Resize(&v, buffersize) < 0)
return NULL;
+ } else {
+ assert(bytesread == bytesrequested);
+ break;
}
}
***************
*** 1519,1523 ****
"read([size]) -> read at most size bytes, returned as a string.\n"
"\n"
! "If the size argument is negative or omitted, read until EOF is reached.");

PyDoc_STRVAR(write_doc,
--- 1544,1550 ----
"read([size]) -> read at most size bytes, returned as a string.\n"
"\n"
! "If the size argument is negative or omitted, read until EOF is reached.\n"
! "Notice that when in non-blocking mode, less data than what was requested\n"
! "may be returned, even if no size parameter was given.");

PyDoc_STRVAR(write_doc,