git/hashmap.h, branch v2.35.2

hashmap: provide deallocation function names

2020-11-02T20:15:50Z

hashmap_free(), hashmap_free_entries(), and hashmap_free_() have existed for a while, but aren't necessarily the clearest names, especially with hashmap_partial_clear() being added to the mix and lazy-initialization now being supported. Peff suggested we adopt the following names[1]: - hashmap_clear() - remove all entries and de-allocate any hashmap-specific data, but be ready for reuse - hashmap_clear_and_free() - ditto, but free the entries themselves - hashmap_partial_clear() - remove all entries but don't deallocate table - hashmap_partial_clear_and_free() - ditto, but free the entries This patch provides the new names and converts all existing callers over to the new naming scheme. [1] https://lore.kernel.org/git/20201030125059.GA3277724@coredump.intra.peff.net/ Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

hashmap: introduce a new hashmap_partial_clear()

2020-11-02T20:15:50Z

merge-ort is a heavy user of strmaps, which are built on hashmap.[ch]. clear_or_reinit_internal_opts() in merge-ort was taking about 12% of overall runtime in my testcase involving rebasing 35 patches of linux.git across a big rename. clear_or_reinit_internal_opts() was calling hashmap_free() followed by hashmap_init(), meaning that not only was it freeing all the memory associated with each of the strmaps just to immediately allocate a new array again, it was allocating a new array that was likely smaller than needed (thus resulting in later need to rehash things). The ending size of the map table on the previous commit was likely almost perfectly sized for the next commit we wanted to pick, and not dropping and reallocating the table immediately is a win. Add some new API to hashmap to clear a hashmap of entries without freeing map->table (and instead only zeroing it out like alloc_table() would do, along with zeroing the count of items in the table and the shrink_at field). Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

hashmap: allow re-use after hashmap_free()

2020-11-02T20:15:50Z

Previously, once map->table had been freed, any calls to hashmap_put(), hashmap_get(), or hashmap_remove() would cause a NULL pointer dereference (since hashmap_free_() also zeros the memory; without that zeroing, calling these functions would cause a use-after-free problem). Modify these functions to check for a NULL table and automatically allocate as needed. Also add a HASHMAP_INIT(fn, data) macro for initializing hashmaps on the stack without calling hashmap_init(). Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

hashmap: adjust spacing to fix argument alignment

2020-11-02T20:15:50Z

No actual code changes; just whitespace adjustments. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

hashmap: add usage documentation explaining hashmap_free[_entries]()

2020-10-13T20:06:37Z

The existence of hashmap_free() and hashmap_free_entries() confused me, and the docs weren't clear enough. We are dealing with a map table, entries in that table, and possibly also things each of those entries point to. I had to consult other source code examples and the implementation. Add a brief note to clarify the differences. This will become even more important once we introduce a new hashmap_partial_clear() function which will add the question of whether the table itself has been freed. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

hashmap_for_each_entry(): workaround MSVC's runtime check failure #3

2020-09-30T20:26:54Z

The OFFSETOF_VAR(var, member) macro is implemented in terms of offsetof(typeof(*var), member) with compilers that know typeof(), but its fallback implemenation compares &(var->member) and (var) and count the distance in bytes, i.e. ((uintptr_t)&(var)->member - (uintptr_t)(var)) MSVC's runtime check, when fed an uninitialized 'var', flags this as a use of an uninitialized variable (and that is legit---uninitialized contents of 'var' is subtracted) in a debug build. After auditing all 6 uses of OFFSETOF_VAR(), 1 of them does feed a potentially uninitialized 'var' to the macro in the beginning of the for() loop: #define hashmap_for_each_entry(map, iter, var, member) \ for (var = hashmap_iter_first_entry_offset(map, iter, \ OFFSETOF_VAR(var, member)); \ var; \ var = hashmap_iter_next_entry_offset(iter, \ OFFSETOF_VAR(var, member))) We can work around this by making sure that var has _some_ value when OFFSETOF_VAR() is called. Strictly speaking, it invites undefined behaviour to use NULL here if we end up with pointer comparison, but MSVC runtime seems to be happy with it, and most other systems have typeof() and don't even need pointer comparison fallback code. Signed-off-by: Junio C Hamano Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

hashmap: fix typo in usage docs

2020-07-28T21:28:15Z

Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

Merge branch 'en/doc-typofix'

2019-12-01T17:04:35Z

Docfix. * en/doc-typofix: Fix spelling errors in no-longer-updated-from-upstream modules multimail: fix a few simple spelling errors sha1dc: fix trivial comment spelling error Fix spelling errors in test commands Fix spelling errors in messages shown to users Fix spelling errors in names of tests Fix spelling errors in comments of testcases Fix spelling errors in code comments Fix spelling errors in documentation outside of Documentation/ Documentation: fix a bunch of typos, both old and new

Fix spelling errors in code comments

2019-11-10T07:00:54Z

Reported-by: Jens Schleusener Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

hashmap: fix documentation misuses of -> versus .

2019-11-07T05:40:56Z

Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano