Skip to content

fix: use manual padding of instance_map_shard #5200

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
Jun 26, 2024
+3 −7
Merged

fix: use manual padding of instance_map_shard #5200

Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
3752a80
Use manual padding of instance_map_shard.
colesbury Jun 26, 2024
94f8b9e
Add 'see #5200'
colesbury Jun 26, 2024
9c37d68
Update include/pybind11/detail/internals.h
henryiii Jun 26, 2024
1c6fc54
Update include/pybind11/detail/internals.h
henryiii Jun 26, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 3 additions & 7 deletions include/pybind11/detail/internals.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -148,18 +148,14 @@ struct override_hash {

using instance_map = std::unordered_multimap<const void *, instance *>;

// ignore: structure was padded due to alignment specifier
PYBIND11_WARNING_PUSH
PYBIND11_WARNING_DISABLE_MSVC(4324)

// Instance map shards are used to reduce mutex contention in free-threaded Python.
struct alignas(64) instance_map_shard {
struct instance_map_shard {
std::mutex mutex;
instance_map registered_instances;
// alignas(64) would be better, but causes compile errors in macOS before 10.14 (see #5200)
char padding[64 - (sizeof(std::mutex) + sizeof(instance_map)) % 64];
};

PYBIND11_WARNING_POP

/// Internal data structure used to track registered instances and types.
/// Whenever binary incompatible changes are made to this structure,
/// `PYBIND11_INTERNALS_VERSION` must be incremented.
Expand Down