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Frédéric Desbiens
d3fb72b6dd
The Linux, Win32 and Win64 simulation ports build a fake initial stack pointer by subtracting a fixed 8 bytes from tx_thread_stack_end. That field addresses the last byte of the thread's stack area, so it is one less than an aligned address and the resulting pointer is misaligned by construction, no matter how well aligned the stack the application supplied was. Two ULONG accesses then use that pointer. _tx_thread_stack_build() itself clears the word below it, and _tx_thread_create() copies it into tx_thread_stack_highest_ptr, which TX_THREAD_STACK_CHECK dereferences on every suspend and resume when TX_ENABLE_STACK_CHECKING is defined. Both are undefined behaviour. They happen to work on x86 but are reported by GCC's undefined behaviour sanitizer, and would fault on a host that requires natural alignment. The fake stack pointer is now rounded down to a ULONG boundary, which leaves it inside the stack area and makes both accesses aligned. Verified by building the Linux port with -fsanitize=undefined and running the demo: the two reported diagnostics are produced before the change and neither appears after it. The tx and smp regression suites pass, 98 and 114 tests respectively. Fixes #218 Assisted-by: Copilot (Opus 5) <noreply@github.com>