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Phase 5.B c14-followup-A: static_assert guard for jit::FrameHeader sizeof
Closes c14 latent silent-break gap per supervisor 00:51:18Z (A) + pythia python#368 missing-validation flag. c14 (0703dba) phx_frame_header_size hardcodes sizeof(void*) for the FrameHeader argument to jit_frame_header_size, matching C++ frameHeaderSize semantics (frame_header.h:67). The hardcoded value is documented as "On 3.12+, FrameHeader = union { PyFunctionObject*; uintptr_t rtfs; } = sizeof(void*)" — comment-derived, NOT static_asserted. If the FrameHeader union grows in a future Python version (or even on 3.12.X minor revisions adding fields), the hardcoded sizeof(void*) silently produces wrong offsets at runtime, re-creating the c14 SIGSEGV class with no compile-time signal. This commit adds a static_assert guard in hir_instr_c_verify.cpp: #if PY_VERSION_HEX >= 0x030C0000 static_assert(sizeof(jit::FrameHeader) == sizeof(void*), "..."); #endif Files: M Python/jit/hir/hir_instr_c_verify.cpp (+15 LOC: include + 5-line static_assert with explanatory comment) Net delta: +15 LOC. Defensive-infra-class commit per docs/methodology/synthetic_falsifier_at_gate.md (1546c43). Synthetic falsifier OPTIONAL given trivial scope (5-LOC static_assert + include) per supervisor 00:51:18Z (A) — would-be falsifier test (intentionally redefining FrameHeader to 16 bytes; verifying static assert FIRES) is symbolic since the FrameHeader struct is defined upstream. PRE-COMMIT BUILD VERIFIED via pre-commit hook a2e8808 — hook re-globs .cpp file via cmake configure, compiles with new static_assert, PASS = current FrameHeader is sizeof(void*) on this build target.
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‎Python/jit/hir/hir_instr_c_verify.cpp‎

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#include "cinderx/Jit/hir/phx_ptr_queue.h" /* Phase 4.X-full X2a (Batch 91) */
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#include "cinderx/Jit/hir/phx_ptr_set.h" /* Phase 4.X-full X2b (Batch 92) */
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#include "cinderx/Jit/hir/phx_ptr_map.h" /* Phase 4.X-full X3a (Batch 95) */
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#include "cinderx/Jit/frame_header.h" /* Phase 5.B c14-followup-A: jit::FrameHeader sizeof guard */
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#include <cassert>
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#include <cstring>
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using namespace jit::hir;
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/* ---- Compile-time size checks ---- */
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/* Phase 5.B c14-followup-A: guard against silent breakage of
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* generator_helpers_c.c::phx_frame_header_size, which hardcodes
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* sizeof(void*) for the FrameHeader argument matching C++
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* frameHeaderSize semantics (frame_header.h:67). On 3.12+, FrameHeader
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* = union { PyFunctionObject*; uintptr_t rtfs; } = sizeof(void*). If the
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* union grows in a future Python version, this static_assert fires AT
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* COMPILE TIME, before the c14 port produces wrong offsets at runtime
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* (the c14 SIGSEGV class). 3.11 branch is dead code per CLAUDE.md. */
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#if PY_VERSION_HEX >= 0x030C0000
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static_assert(sizeof(jit::FrameHeader) == sizeof(void*),
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"jit::FrameHeader size assumption broken — c14 phx_frame_header_size "
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"would produce wrong offsets; revisit hardcoded sizeof(void*) in "
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"generator_helpers_c.c::phx_frame_header_size.");
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#endif
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static_assert(sizeof(HirInstrLayout) == sizeof(Instr),
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"HirInstr size must match C++ Instr");
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static_assert(sizeof(HirCondBranchInstr) == sizeof(CondBranchBase),

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