Otherwise it complains about a set but unused variable:
```
../src/basic/hashmap.c:1070:48: error: variable 'n_rehashed' set but not used [-Werror,-Wunused-but-set-variable]
unsigned old_n_buckets, new_n_buckets, n_rehashed, new_n_entries;
^
1 error generated.
```
Before we had the following scheme:
mempool_enabled() would check mempool_use_allowed, and
libsystemd-shared would be linked with a .c file that provides mempool_use_allowed=true,
while other things would linked with a different .c file with mempool_use_allowed=false.
In the new scheme, mempool_enabled() itself is a weak symbol. If it's
not found, we assume false. So it only needs to be provided for libsystemd-shared,
where it can return false or true.
test-set-disable-mempool is libshared, so it gets the symbol. But then we
actually disable the mempool via envvar. mempool_enable() is called to check
its return value directly.
Note, if `n != SIZE_MAX`, we cannot check the existence of the specified
string in the set without duplicating the string. And, set_consume() also
checks the existence of the string. Hence, it is not necessary to call
set_contains() if `n != SIZE_MAX`.
In general we almost never hit those asserts in production code, so users see
them very rarely, if ever. But either way, we just need something that users
can pass to the developers.
We have quite a few of those asserts, and some have fairly nice messages, but
many are like "WTF?" or "???" or "unexpected something". The error that is
printed includes the file location, and function name. In almost all functions
there's at most one assert, so the function name alone is enough to identify
the failure for a developer. So we don't get much extra from the message, and
we might just as well drop them.
Dropping them makes our code a tiny bit smaller, and most importantly, improves
development experience by making it easy to insert such an assert in the code
without thinking how to phrase the argument.
Before we invoke n_entries() we need to check for non-NULL here, like in
all other calls to the helper function. Otherwise we'll crash when
invoked with a NULL object, which we usually consider equivalent to an
empty one though.
We recently started making more use of malloc_usable_size() and rely on
it (see the string_erase() story). Given that we don't really support
sytems where malloc_usable_size() cannot be trusted beyond statistics
anyway, let's go fully in and rework GREEDY_REALLOC() on top of it:
instead of passing around and maintaining the currenly allocated size
everywhere, let's just derive it automatically from
malloc_usable_size().
I am mostly after this for the simplicity this brings. It also brings
minor efficiency improvements I guess, but things become so much nicer
to look at if we can avoid these allocation size variables everywhere.
Note that the malloc_usable_size() man page says relying on it wasn't
"good programming practice", but I think it does this for reasons that
don't apply here: the greedy realloc logic specifically doesn't rely on
the returned extra size, beyond the fact that it is equal or larger than
what was requested.
(This commit was supposed to be a quick patch btw, but apparently we use
the greedy realloc stuff quite a bit across the codebase, so this ends
up touching *a*lot* of code.)
The commit 6f3ac0d517 drops the prefix and
suffix in TAGS= property. But there exists several rules that have like
`TAGS=="*:tag:*"`. So, the property must be always prefixed and suffixed
with ":".
Fixes#17930.
if we allocate a bunch of hash tables all at the same time, with none
earlier than the other, there's a good chance we'll initialize the
shared hash key multiple times, so that some threads will see a
different shared hash key than others.
Let's fix that, and make sure really everyone sees the same hash key.
Fixes: #17007
I think this is nicer in general, and here in particular we have a lot
of code like:
static inline IteratedCache* hashmap_iterated_cache_new(Hashmap *h) {
return (IteratedCache*) _hashmap_iterated_cache_new(HASHMAP_BASE(h));
}
and it's visually appealing to use the same whitespace in the function
signature and the cast in the body of the function.
The compiler would do this to, esp. with LTO, but we can short-circuit the
whole process and make everything a bit simpler by avoiding the separate
definition.
(It would be nice to do the same for _set_new(), _set_ensure_allocated()
and other similar functions which are one-line trivial wrappers too. Unfortunately
that would require enum HashmapType to be made public, which we don't want
to do.)
Also use double space before the tracking args at the end. Without
the comma this looks ugly, but it's a bit better with the double space.
At least it doesn't look like a variable with a type.
This combines set_ensure_allocated() with set_consume(). The cool thing is that
because we know the hash ops, we can correctly free the item if appropriate.
Similarly to set_consume(), the goal is to simplify handling of the case where
the item needs to be freed on error and if already present in the set.
It's such a common operation to allocate the set and put an item in it,
that it deserves a helper. set_ensure_put() has the same return values
as set_put().
Comes with tests!
"internal" is a lot of characters. Let's take a leaf out of the Python's book
and simply use _ to mean private. Much less verbose, but the meaning is just as
clear, or even more.
If we're using a set with _put_strdup(), most of the time we want to use
string hash ops on the set, and free the strings when done. This defines
the appropriate a new string_hash_ops_free structure to automatically free
the keys when removing the set, and makes set_put_strdup() and set_put_strdupv()
instantiate the set with those hash ops.
hashmap_put_strdup() was already doing something similar.
(It is OK to instantiate the set earlier, possibly with a different hash ops
structure. set_put_strdup() will then use the existing set. It is also OK
to call set_free_free() instead of set_free() on a set with
string_hash_ops_free, the effect is the same, we're just overriding the
override of the cleanup function.)
No functional change intended.
So far, we'd use hashmap_free_free to free both keys and values along with
the hashmap. I think it's better to make this more encapsulated: in this variant
the way contents are freed can be decided when the hashmap is created, and
users of the hashmap can always use hashmap_free.
Using C11 thread-local storage in destructors causes uninitialized
read. Let's avoid that using a direct comparison instead of using
the cached values. As this code path is taken only when compiled
with -DVALGRIND=1, the performance cost shouldn't matter too much.
Fixes#12814
internal_hashmap_first_key_and_value() returns the first value, or %NULL
if the hashmap is empty.
However, hashmaps may contain %NULL values. That means, a caller getting
%NULL doesn't know whether the hashmap is empty or whether the first
value is %NULL.
For example, a caller may be tempted to do something like:
if ((val = hashmap_steal_first_key_and_value (h, (void **) key))) {
// process first entry.
}
But this is only correct if the caller made sure that the hash is either
not empty or contains no NULL values.
Anyway, since a %NULL return value can signal an empty hash or a %NULL
value, it seems error prone to leave the key output argument
uninitialized in situations that the caller cannot clearly distinguish
(without making additional assumptions).
GCC 8.2 with LTO and -O2 emits a false warning:
src/basic/hashmap.c: In function 'internal_hashmap_free.constprop':
src/basic/hashmap.c:898:33: error: 'k' may be used uninitialized in this function [-Werror=maybe-uninitialized]
free_key(k);
^
Avoid it by initializing the variable.
Let's first remove an item from the hashmap and only then destroy it.
This makes sure that destructor functions can mdoify the hashtables in
their own codee and we won't be confused by that.
