"Memory free event without a matching allocation" when using std::format with {:L}

[adriengivry]

Description

On the game engine I'm working on, using C++20 and std::format, it seems like the Tracy profiler encounters a "Memory free event without a matching allocation" when using std::format(std::locale(""), "{:L}", 10).

For reference, here are the operators we overloaded:

void* operator new(std::size_t size);
void operator delete(void* ptr) noexcept;
void operator delete(void* ptr, std::size_t size) noexcept;
void* operator new[](std::size_t size);
void operator delete[](void* ptr) noexcept;
void operator delete[](void* ptr, std::size_t size) noexcept;
void* operator new(std::size_t size, const std::nothrow_t&) noexcept;
void operator delete(void* ptr, const std::nothrow_t&) noexcept;
void* operator new[](std::size_t size, const std::nothrow_t&) noexcept;
void operator delete[](void* ptr, const std::nothrow_t&) noexcept;
void* operator new(std::size_t size, std::align_val_t alignment);
void operator delete(void* ptr, std::align_val_t alignment) noexcept;
void* operator new[](std::size_t size, std::align_val_t alignment);
void operator delete[](void* ptr, std::align_val_t alignment) noexcept;
void operator delete(void* ptr, std::size_t size, std::align_val_t alignment) noexcept;
void operator delete[](void* ptr, std::size_t size, std::align_val_t alignment) noexcept;
void* operator new(std::size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept;
void operator delete(void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept;

It works fine when using std::locale(), which defaults to the C locale.

Note: std::locale("") being the user's locale (from its regional settings). In my case, it's en_US

Expected Behaviour

Not sure, is it a false positive, or is there something wrong with std::format?

Environment

MSVC: Microsoft (R) C/C++ Optimizing Compiler Version 19.42.34438 for x86

[mcourteaux]

I'm assuming you did a global new and delete override, or even more tricky a global malloc() and free() override. Might be an internal allocation happening in the standard C++ library, which gets executed before Tracy's static initializers ran. These are super hard to fix. Tracy has an option to ignore those errors, however this option is not yet user controllable. You can modify Tracy source code here:

tracy/server/TracyWorker.cpp

Line 2750 in e656d49

m_ignoreMemFreeFaults = ( welcome.flags & WelcomeFlag::OnDemand ) || ( welcome.flags & WelcomeFlag::IsApple );

to check for an environment variable, for example: || getenv("TRACY_IGNORE_MEM_FREE_FAULT").

[adriengivry]

So far our workaround has been to avoid using std::locale("") when tracy memory profiling is enabled. We're definitely looking for a more future-proof solution, so we'll look into that recommendation.

I've update the issue description to include the operators we tried to overload.