Remove map_free macros#4166
Merged
ethomson merged 2 commits intolibgit2:masterlibgit2/libgit2:masterfrom Mar 20, 2017
Merged
Conversation
We currently call `git_strmap_free` on `checkout_data.mkdir_map` in the `checkout_data_clear` function. The only thing protecting us from a double-free is that the `git_strmap_free` function is in fact not a function, but a macro that also sets the map to NULL. Remove the second call to `git_strmap_free` and explicitly set the map member to NULL.
The `map_free` functions were not implemented as functions but instead
as macros which also set the map to NULL. While this is most certainly
sensible in most cases, we should prefer the more obvious behavior,
namingly leaving the map pointer intact.
Furthermore, this macro has been refactored incorrectly during the
map-refactorings: the two statements are not actually grouped together
by a `do { ... } while (0)` block, as it is required for macros to
match the behavior of functions more closely. This has led to at least
one subtle nesting error in `pack-objects.c`. The following code block
```
if (pb->object_ix)
git_oidmap_free(pb->object_ix);
```
would be expanded to
```
if (pb->object_ix)
git_oidmap__free(pb->object_ix); pb->object_ix = NULL;
```
which is not what one woudl expect. While it is not a bug here as it
would simply become a no-op, the wrong implementation could lead to bugs
in other occasions.
Fix this by simply removing the macro altogether and replacing it with
real function calls. This leaves the burden of setting the pointer to
NULL afterwards to the caller, but this is actually expected and behaves
like other `free` functions.
Member
|
👍 |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
I just noticed a subtle bug via Coverity which I introduced in my recent refactoring of the map interfaces. The
git_map_freefunctions were implemented as macros, but in fact in a subtly wrong way where the statements were not grouped together by ado { ... } while (0)block. I think no real issues were introduced by this, but I took it as a hint to remove the macro altogether. One caller needed to be fixed, but this was a double-free anyway and as such wrong.