lazymanifest: avoid reading uninitialized memory
I got errors running tests with clang UBSAN [1] enabled. One of them is:
```
--- test-dirstate.t
+++ test-dirstate.t.err
@@ -85,9 +85,115 @@
$ echo "[extensions]" >> .hg/hgrc
$ echo "dirstateex=../dirstateexception.py" >> .hg/hgrc
$ hg up 0
- abort: simulated error while recording dirstateupdates
- [255]
+ mercurial/cext/manifest.c:781:13: runtime error: load of value 190, which is not a valid value for type 'bool'
+ #0 0x7f668a8cf748 in lazymanifest_diff mercurial/cext/manifest.c:781
+ #1 0x7f6692fc1dc4 in call_function Python-2.7.11/Python/ceval.c:4350
+ .......
+ SUMMARY: UndefinedBehaviorSanitizer: invalid-bool-load mercurial/cext/manifest.c:781:13 in
+ [1]
$ hg log -r . -T '{rev}\n'
1
$ hg status
- ? a
```
While the code is not technically wrong, but switching the condition would
make clang UBSAN happy. So let's do it.
The uninitialized memory could come from, for example, `lazymanifest_copy`
allocates `self->maxlines` items but only writes the first `self->lines`
items.
[1]: https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html
Test Plan:
Run `test-dirstate.t` with UBSAN and it no longer reports the issue.
Differential Revision: https://phab.mercurial-scm.org/D1948
--- a/mercurial/cext/manifest.c Fri Jan 26 11:42:47 2018 -0800
+++ b/mercurial/cext/manifest.c Tue Jan 30 20:32:48 2018 -0800
@@ -778,11 +778,11 @@
PyObject *outer;
/* If we're looking at a deleted entry and it's not
* the end of the manifest, just skip it. */
- if (left->deleted && sneedle < self->numlines) {
+ if (sneedle < self->numlines && left->deleted) {
sneedle++;
continue;
}
- if (right->deleted && oneedle < other->numlines) {
+ if (oneedle < other->numlines && right->deleted) {
oneedle++;
continue;
}