Previously, the reference count for a newly created CacheDir had been
set to 1 in CacheNewDir. This was wrong because at that point, the
object had not been referenced by any nonlocal variable. The reference
count is no longer incremented at this point.
All callers of CacheNewDir either append the newly created CachedDir to
a SearchPath via Lst_Append and CachedDir_Ref, or they assign it to a
global variable via CachedDir_Assign.
Since the reference count is no longer wrongly incremented, it does not
need to be decremented more than necessary in Dir_End. To keep the code
simple and maintainable, all assignments to global variables are now
handled by CachedDir_Assign. Adding a CachedDir to a list is still done
manually via Lst_Append, and the corresponding code for decrementing is
in SearchPath_Clean and SearchPath_Free. These details may be cleaned
up in a follow-up commit.
As a result, when OpenDirs_Done is called in the unit tests, the list of
open directories is empty. It had been non-empty in a single unit test
before (dep-wildcards.mk), as a result of calling Dir_Expand.
The additional debug logging for the reference counting is not enabled
by default since it contains memory addresses, which makes the output
dependent on the memory allocator.
The function CachedDir_Destroy has been merged into CachedDir_Undef,
which had only been used in Dir_End before. The new name emphasizes
that it corresponds to CachedDir_Ref.
The memory management for dotLast is quite simple. It is initialized
exactly once main_Init > Init_Objdir > Dir_InitDir and freed exactly
once in main_CleanUp > Dir_End. Previously, dotLast was not freed at all.
The first call to CachedDir_Unref decremented the refCount to 0 but
didn't free anything. Next, CachedDir_Destroy was called, which
decremented the reference count to -1, therefore skipping the actual
freeing. This was probably an implementation mistake.
Since Dir_End is called at the very end of main_CleanUp, no code
accesses dotLast after it has been freed.
In a makefile with repeated ".CURDIR=." lines, Dir_AddDir is called with
a NULL path, once per line. Since the path is NULL, the search for
OpenDirs_Find is skipped and the directory is always read from disk.
The freshly read directory has a refCount of 1, and the refCount never
raises above 2.
In Dir_InitCur, the directory of the previous .CURDIR has a refCount of
2, which is decremented twice and then freed. After this, the new
directory is placed in the global 'cur', after incrementing its refCount
to 2.
It still seems wrong that the refCount of 'cur' is 2 instead of 1, but
it works well.
The function Dir_Destroy is an implementation detail of the cached
directories, and it should not be exported to the other modules. The
search paths, on the other hand, are the high-level API that may be used
by the other modules, as the concept of search paths is documented in
the manual page.
I'm not really happy with this, but my lack of confidence in the
remaining question marks about this (no real documentation about the
underlying physical processes, and a slightly self-inconsistent uefi
spec) is outweighed by the value of not distracting people with
entropy warnings on systems that are almost certainly fine.
