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hbitmap: Fix merge when b is empty, and result is not an alias of a 

Nobody calls the function like this currently, but we neither prohibit
or cope with this behavior. I decided to make the function cope with it.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190709232550.10724-8-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
John Snow 2019-07-29 16:35:53 -04:00
parent cf0cd293c6
commit 3bde4b010e
1 changed files with 10 additions and 3 deletions
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13
util/hbitmap.c
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@ -785,8 +785,9 @@ bool hbitmap_can_merge(const HBitmap *a, const HBitmap *b)
}
/**
* Given HBitmaps A and B, let A := A (BITOR) B.
* Bitmap B will not be modified.
* Given HBitmaps A and B, let R := A (BITOR) B.
* Bitmaps A and B will not be modified,
* except when bitmap R is an alias of A or B.
*
* @return true if the merge was successful,
* false if it was not attempted.
@ -801,7 +802,13 @@ bool hbitmap_merge(const HBitmap *a, const HBitmap *b, HBitmap *result)
}
assert(hbitmap_can_merge(b, result));
if (hbitmap_count(b) == 0) {
if ((!hbitmap_count(a) && result == b) ||
(!hbitmap_count(b) && result == a)) {
return true;
}
if (!hbitmap_count(a) && !hbitmap_count(b)) {
hbitmap_reset_all(result);
return true;
}