Error messages should be sentence fragments, and therefore:
1. Should not begin with a capital letter,
2. Should not conclude with punctuation, and
3. Should not end a sentence and begin a new one
The header src/cc-compat.h defines portable format specifiers PRIuZ, PRIdZ, and PRIxZ. The original report highlighted the need to use these specifiers in examples/network/fetch.c. For this commit, I checked all C source and header files not in deps/ and transitioned to the appropriate format specifier where appropriate.
It is obviously quite a serious problem if this happens, but mutex
initialization can fail and we should detect it. It's a bit like
a memory allocation failure, in that you're probably pretty screwed
if this occurs, but at least we'll catch it.
By zeroing out the memory when we free larger objects (i.e. those
that serve as collections of other data, such as repos, odb, refdb),
I'm hoping that it will be easier for libgit2 bindings to find
errors in their object management code.
This adds docs for the cache control options to git_libgit2_opts
and also tweaks the cache code so that if the cache is disabled,
then the next time we attempt to insert something into the cache
in question, we will actually clear any old cached objects.
This adds create and free callback to the git_objects_table so
that more of the creation and destruction of objects can be table
driven instead of using switch statements. This also makes the
semantics of certain object creation functions consistent so that
we can make better use of function pointers. This also fixes a
theoretical error case where an object allocation fails and we
end up storing NULL into the cache.
Add a git_cache_set_max_object_size method that does more checking
around setting the max object size. Also add a git_cache_size to
read the number of objects currently in the cache. This makes it
easier to write tests.
Example: a cached node is owned only by the cache (refcount == 1).
Thread A holds the lock and determines that the entry which should get
cached equals the node (git_oid_cmp(&node->oid, &entry->oid) == 0).
It frees the given entry to instead return the cached node to the user
(entry = node). Now, before Thread A happens to increment the refcount
of the node *outside* the cache lock, Thread B tries to store another
entry and hits the slot of the node before, decrements its refcount and
frees it *before* Thread A gets a chance to increment for the user.
git_cached_obj_incref(entry);
git_mutex_lock(&cache->lock);
{
git_cached_obj *node = cache->nodes[hash & cache->size_mask];
if (node == NULL) {
cache->nodes[hash & cache->size_mask] = entry;
} else if (git_oid_cmp(&node->oid, &entry->oid) == 0) {
git_cached_obj_decref(entry, cache->free_obj);
entry = node;
} else {
git_cached_obj_decref(node, cache->free_obj);
// Thread B is here
cache->nodes[hash & cache->size_mask] = entry;
}
}
git_mutex_unlock(&cache->lock);
// Thread A is here
/* increase the refcount again, because we are
* returning it to the user */
git_cached_obj_incref(entry);
