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)".
$ echo "[extensions]" >> $HGRCPATH
$ echo "rebase=" >> $HGRCPATH
initialize repository
$ hg init
$ echo 'a' > a
$ hg ci -A -m "0"
adding a
$ echo 'b' > b
$ hg ci -A -m "1"
adding b
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo 'c' > c
$ hg ci -A -m "2"
adding c
created new head
$ echo 'd' > d
$ hg ci -A -m "3"
adding d
$ hg bookmark -r 1 one
$ hg bookmark -r 3 two
$ hg up -q two
bookmark list
$ hg bookmark
one 1:925d80f479bb
* two 3:2ae46b1d99a7
rebase
$ hg rebase -s two -d one
rebasing 3:2ae46b1d99a7 "3" (tip two)
saved backup bundle to $TESTTMP/.hg/strip-backup/2ae46b1d99a7-e6b057bc-backup.hg (glob)
$ hg log
changeset: 3:42e5ed2cdcf4
bookmark: two
tag: tip
parent: 1:925d80f479bb
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 3
changeset: 2:db815d6d32e6
parent: 0:f7b1eb17ad24
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 2
changeset: 1:925d80f479bb
bookmark: one
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 1
changeset: 0:f7b1eb17ad24
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
aborted rebase should restore active bookmark.
$ hg up 1
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
(leaving bookmark two)
$ echo 'e' > d
$ hg ci -A -m "4"
adding d
created new head
$ hg bookmark three
$ hg rebase -s three -d two
rebasing 4:dd7c838e8362 "4" (tip three)
merging d
warning: conflicts while merging d! (edit, then use 'hg resolve --mark')
unresolved conflicts (see hg resolve, then hg rebase --continue)
[1]
$ hg rebase --abort
rebase aborted
$ hg bookmark
one 1:925d80f479bb
* three 4:dd7c838e8362
two 3:42e5ed2cdcf4
after aborted rebase, restoring a bookmark that has been removed should not fail
$ hg rebase -s three -d two
rebasing 4:dd7c838e8362 "4" (tip three)
merging d
warning: conflicts while merging d! (edit, then use 'hg resolve --mark')
unresolved conflicts (see hg resolve, then hg rebase --continue)
[1]
$ hg bookmark -d three
$ hg rebase --abort
rebase aborted
$ hg bookmark
one 1:925d80f479bb
two 3:42e5ed2cdcf4