If a file is opened with an explicit buffer size >= 1, repeated
close() calls would attempt to free() the buffer already free()ed on
the first close(). [bug introduced with patch #788249]
Making sure that the buffer is free()ed in file object deallocation is
a belt-n-braces bit of insurance against a memory leak.
Obtain cleaner coding and a system wide
performance boost by using the fast, pre-parsed
PyArg_Unpack function instead of PyArg_ParseTuple
function which is driven by a format string.
[#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.
For a file f, iter(f) now returns f (unless f is closed), and f.next()
is similar to f.readline() when EOF is not reached; however, f.next()
uses a readahead buffer that messes up the file position, so mixing
f.next() and f.readline() (or other methods) doesn't work right.
Calling f.seek() drops the readahead buffer, but other operations
don't.
The real purpose of this change is to reduce the confusion between
objects and their iterators. By making a file its own iterator, it's
made clearer that using the iterator modifies the file object's state
(in particular the current position).
A nice side effect is that this speeds up "for line in f:" by not
having to use the xreadlines module. The f.xreadlines() method is
still supported for backwards compatibility, though it is the same as
iter(f) now.
(I made some cosmetic changes to Oren's code, and added a test for
"file closed" to file_iternext() and file_iter().)
MSDN sample programs use it, apparently in error. The correct name
is WIN32_LEAN_AND_MEAN. After switching to the correct name, in two
cases more was needed because the code actually relied on things that
disappear when WIN32_LEAN_AND_MEAN is defined.
don't understand how this function works, also beefed up the docs. The
most common usage error is of this form (often spread out across gotos):
if (_PyString_Resize(&s, n) < 0) {
Py_DECREF(s);
s = NULL;
goto outtahere;
}
The error is that if _PyString_Resize runs out of memory, it automatically
decrefs the input string object s (which also deallocates it, since its
refcount must be 1 upon entry), and sets s to NULL. So if the "if"
branch ever triggers, it's an error to call Py_DECREF(s): s is already
NULL! A correct way to write the above is the simpler (and intended)
if (_PyString_Resize(&s, n) < 0)
goto outtahere;
Bugfix candidate.
