C++26 Introduces New Debugging Header with Standardized Breakpoint Functions

Standardizing Debugger Interaction

C++26 will standardize programmatic debugging features through the new `<debugging>` header, based on proposals P2546R5 and P2810R4. This standardization addresses the common practice of C++ projects creating their own platform-specific code for debugger interaction, such as `Boost.Test`'s `debugger_break()` or `Catch2`'s `CATCH_BREAK_INTO_DEBUGGER`.

New Debugging Functions

The `<debugging>` header introduces three `noexcept` and freestanding functions. `std::breakpoint()` provides an unconditional breakpoint, halting execution when a debugger is attached. If no debugger is present, its behavior is implementation-defined, typically resulting in a signal like `SIGTRAP`.

`std::is_debugger_present()` returns `true` if a debugger is currently tracing the program. This check is performed on each call, as debugger attachment status can change during execution. The underlying mechanism varies by platform, such as `::IsDebuggerPresent()` on Windows or checking `/proc/self/status` on Linux.

Replaceability for Freestanding Environments

A key feature of `std::is_debugger_present()` is its replaceability, similar to `operator new` and `operator delete`. This allows developers to define custom implementations, which is crucial for bare-metal or freestanding platforms where OS-level debugger detection might not exist. Without replaceability, the function would either be excluded from freestanding environments or provide a non-functional default.

`std::breakpoint_if_debugging()` is a convenience function that combines the other two, executing a breakpoint only if a debugger is attached. This function simplifies a common debugging pattern previously implemented manually across various frameworks.