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Fix DenseThreadId static destruction order fiasco #12789

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Merged
bneradt merged 1 commit into from
Jan 8, 2026
Merged

Fix DenseThreadId static destruction order fiasco #12789

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32 changes: 11 additions & 21 deletions include/tsutil/DenseThreadId.h
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Original file line number Diff line number Diff line change
Expand Up @@ -27,21 +27,19 @@

#include "tsutil/Assert.h"

#include <array>
#include <cstddef>
#include <mutex>
#include <vector>

// Provide an alternate thread id, suitible for use as an array index.
// Provide an alternate thread id, suitable for use as an array index.
//
class DenseThreadId
{
public:
// This can onlhy be called during single-threaded initialization.
//
static void
set_num_possible_values(std::size_t num_possible_values)
static constexpr std::size_t
num_possible_values()
{
_num_possible_values = num_possible_values;
return _num_possible_values;
}

static std::size_t
Expand All @@ -50,23 +48,15 @@ class DenseThreadId
return _id.val;
}

static std::size_t
num_possible_values()
{
return _num_possible_values;
}

private:
inline static std::mutex _mtx;
inline static std::vector<std::size_t> _id_stack;
inline static std::size_t _stack_top_idx;
inline static std::size_t _num_possible_values{256};
static constexpr std::size_t _num_possible_values{256};
inline static std::mutex _mtx;
inline static std::array<std::size_t, _num_possible_values> _id_stack;
inline static std::size_t _stack_top_idx;

static void
_init()
{
_id_stack.resize(_num_possible_values);

_stack_top_idx = 0;
for (std::size_t i{0}; i < _num_possible_values; ++i) {
_id_stack[i] = i + 1;
Expand All @@ -82,8 +72,8 @@ class DenseThreadId
_init();
_inited = true;
}
if (_id_stack.size() == _stack_top_idx) {
fatal_error("DenseThreadId: number of threads exceeded maximum {}", unsigned(_id_stack.size()));
if (_num_possible_values == _stack_top_idx) {
fatal_error("DenseThreadId: number of threads exceeded maximum {}", unsigned(_num_possible_values));
}
val = _stack_top_idx;
_stack_top_idx = _id_stack[_stack_top_idx];
Expand Down