util: add iterfile to workaround a fileobj.__iter__ issue with EINTR
The fileobj.__iter__ implementation in Python 2.7.12 (hg changeset
45d4cea97b04) is buggy: it cannot handle EINTR correctly.
In Objects/fileobject.c:
size_t Py_UniversalNewlineFread(....) {
....
if (!f->f_univ_newline)
return fread(buf, 1, n, stream);
....
}
According to the "fread" man page:
If an error occurs, or the end of the file is reached, the return value
is a short item count (or zero).
Therefore it's possible for "fread" (and "Py_UniversalNewlineFread") to
return a positive value while errno is set to EINTR and ferror(stream)
changes from zero to non-zero.
There are multiple "Py_UniversalNewlineFread": "file_read", "file_readinto",
"file_readlines", "readahead". While the first 3 have code to handle the
EINTR case, the last one "readahead" doesn't:
static int readahead(PyFileObject *f, Py_ssize_t bufsize) {
....
chunksize = Py_UniversalNewlineFread(
f->f_buf, bufsize, f->f_fp, (PyObject *)f);
....
if (chunksize == 0) {
if (ferror(f->f_fp)) {
PyErr_SetFromErrno(PyExc_IOError);
....
}
}
....
}
It means "readahead" could ignore EINTR, if "Py_UniversalNewlineFread"
returns a non-zero value. And at the next time "readahead" got executed, if
"Py_UniversalNewlineFread" returns 0, "readahead" would raise a Python error
without a incorrect errno - could be 0 - thus "IOError: [Errno 0] Error".
The only user of "readahead" is "readahead_get_line_skip".
The only user of "readahead_get_line_skip" is "file_iternext", aka.
"fileobj.__iter__", which should be avoided.
There are multiple places where the pattern "for x in fp" is used. This
patch adds a "iterfile" method in "util.py" so we can migrate our code from
"for x in fp" to "fox x in util.iterfile(fp)".
#!/bin/sh
#
# This is an example of using HGEDITOR to create of diff to review the
# changes while committing.
# If you want to pass your favourite editor some other parameters
# only for Mercurial, modify this:
case "${EDITOR}" in
"")
EDITOR="vi"
;;
emacs)
EDITOR="$EDITOR -nw"
;;
gvim|vim)
EDITOR="$EDITOR -f -o"
;;
esac
HGTMP=""
cleanup_exit() {
rm -rf "$HGTMP"
}
# Remove temporary files even if we get interrupted
trap "cleanup_exit" 0 # normal exit
trap "exit 255" HUP INT QUIT ABRT TERM
HGTMP=$(mktemp -d ${TMPDIR-/tmp}/hgeditor.XXXXXX)
[ x$HGTMP != x -a -d $HGTMP ] || {
echo "Could not create temporary directory! Exiting." 1>&2
exit 1
}
(
grep '^HG: changed' "$1" | cut -b 13- | while read changed; do
"$HG" diff "$changed" >> "$HGTMP/diff"
done
)
cat "$1" > "$HGTMP/msg"
MD5=$(which md5sum 2>/dev/null) || \
MD5=$(which md5 2>/dev/null)
[ -x "${MD5}" ] && CHECKSUM=`${MD5} "$HGTMP/msg"`
if [ -s "$HGTMP/diff" ]; then
$EDITOR "$HGTMP/msg" "$HGTMP/diff" || exit $?
else
$EDITOR "$HGTMP/msg" || exit $?
fi
[ -x "${MD5}" ] && (echo "$CHECKSUM" | ${MD5} -c >/dev/null 2>&1 && exit 13)
mv "$HGTMP/msg" "$1"
exit $?