AnyPS5/docs/dev/debt/libSceAmpr.md

# libSceAmpr technical debt

### Unknown function info

- [AMPR command buffer null arguments](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) - the result for a null command buffer is unknown for `sceAmprCommandBufferConstructor`, `sceAmprAprCommandBufferConstructor`, `sceAmprCommandBufferReset` and `sceAmprCommandBufferSetBuffer`; these return `SCE_KERNEL_ERROR_EINVAL` here, but the behavior has not been confirmed on a PS5.
- [AMPR WriteAddressFromCounterPairOnCompletion](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) - the pair of an even counter n is assumed to give counter n in the low 32 bits and n + 1 in the high 32 bits. Wait compare values, wait flush and counter index ranges follow the [ampr_emu](https://github.com/drakmor/ampr_emu) reimplementation; the flush is accepted and has no effect, as commands run in order
- [AMPR command buffer offsets](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) - recording with a current offset greater than the bound memory size throws before calculating remaining capacity or writing a command. This validates the emulator's own command-buffer encoding; the console's response to a corrupted opaque buffer object is unknown.
- [AMPR command sizes](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) - commands use the emulator's own encoding with an 8-byte header, so `Nop(n)` takes 8 + 4n bytes where the console record is n dwords including its header (`NopWithData(n)`: (n + 1) dwords). The measure functions agree with the appended sizes, but a title that pads to an exact offset or the end of the buffer with `Nop(remaining / 4)` gets `SCE_KERNEL_ERROR_EBUSY` or a shifted offset. The at-start flag of the `_04_00` writes is ignored; commands run in order, each after the previous one completes
- [APR map begin and end](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) - as in ampr_emu, `MapBegin`/`MapDirectBegin` map when they run and `MapEnd` only closes the region; while a region is open a second begin and every completion write return `EPERM`, the at-start `_04_00` writes are accepted
- [AMPR markers](../../../core/libs/prx/libSceAmpr/Export.cpp): colors are not recorded and command sizes use the host encoding. Native signatures confirm that set takes a color pointer and push/measure take the color value.
- [__cxa_call_unexpected](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) - takes the in-flight exception's unwind header and never returns, as [libcxxabi 18.1.8](https://github.com/llvm/llvm-project/blob/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff/libcxxabi/src/cxa_personality.cpp#L1171-L1211) does. No `std::set_unexpected` is exported and the exception header's unexpected handler is never set, so the handler is always the default one, which calls `std::terminate` ([cxa_default_handlers.cpp](https://github.com/llvm/llvm-project/blob/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff/libcxxabi/src/cxa_default_handlers.cpp#L88-L99)); it therefore forwards to libc's `__cxa_call_terminate`, which begins the catch and runs the current terminate handler. That matches libcxxabi except for which terminate handler runs: there `std::terminate` after `__cxa_begin_catch` ([cxa_exception.cpp L470-L477](https://github.com/llvm/llvm-project/blob/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff/libcxxabi/src/cxa_exception.cpp#L470-L477)) runs the handler saved in the caught exception's header ([cxa_handlers.cpp L72-L93](https://github.com/llvm/llvm-project/blob/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff/libcxxabi/src/cxa_handlers.cpp#L72-L93)), which `__cxa_throw` and `__cxa_init_primary_exception` set to `std::get_terminate()` when the exception is thrown ([cxa_exception.cpp L209-L214](https://github.com/llvm/llvm-project/blob/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff/libcxxabi/src/cxa_exception.cpp#L209-L214), [L279](https://github.com/llvm/llvm-project/blob/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff/libcxxabi/src/cxa_exception.cpp#L279)), while here the current global handler runs, as AnyPS5's own `std::terminate` does. The two differ only if `std::set_terminate` was called between the throw and this call. A null header terminates because this emulator's libc `__cxa_begin_catch` terminates on null (libcxxabi does not define that case). Dynamic exception specifications that would let a replaced unexpected handler throw a permitted type are not modelled

### Functional

- [sceAmprAmmGetUsageStatsData](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) fills the caller-sized 24-byte statistics structure with 512 page-table pool entries, no allocated entries, a zero high watermark and ring idle flags 0x7, the constants of [KytyPS5](https://github.com/KytyPS5/KytyPS5/blob/main/src/libs/libAmpr.cpp); they are not measured on a console, and the real call is a pass-through to `sceKernelMapperGetUsageStatsData` per [drakmor/ampr_emu](https://github.com/drakmor/ampr_emu/blob/main/src/ampr_emu_amm.cpp), which this port has no kernel-side counterpart for.
- [Dinkumware thread exports](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) follow the Dinkumware threads library shipped with [Visual C++ 2013](https://github.com/adityaramesh/concurrency_runtime/tree/master/VS2013_SP2/crt/src/thr) (`cthread.c`) and its `atomic.c`, [microsoft/STL `cthread.cpp`](https://github.com/microsoft/STL/blob/main/stl/src/cthread.cpp) and C11 Annex K, without console verification. The spin lock (byte exchange loop, no yield) matches that disassembly. The shared_ptr spin lock is one process-wide flag that yields while it spins. `wcstombs_s` is `wcsrtombs_s` with a fresh conversion state, so `*retval` excludes the terminating null as in Annex K, not as in the Microsoft CRT, and `_TRUNCATE` has no meaning.
- [_Cnd_init_with_name](../../../core/libs/prx/libSceAmpr/Export.cpp) (libSceAmpr) - takes a pointer to the handle slot like the libc `_Cnd_*` exports from [#3079](https://github.com/boykopovar/AnyPS5/pull/3079) and acts on the same conditions. The signature `_Cnd_init_with_name(_Cnd_t*, const char* name)` is inferred from [fpPS4 `ps4_mtx_internal.pas`](https://github.com/red-prig/fpPS4/blob/trunk/src/libcinternal/ps4_mtx_internal.pas), where the PS4 `_Mtx_init` is `_Mtx_init_with_name` with the name `SceLibcI_Mtx` and the name only reaches the pthread object; here it is `_Cnd_init` and the name, which may be null, is ignored. This is not confirmed on a PS5 `libc.prx`.