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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.
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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.