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ffi: reject multi-argument buffer fast trampolines - #67046
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## main #67046 +/- ##
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- Coverage 90.73% 90.71% -0.02%
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Files 798 798
Lines 279993 279995 +2
Branches 53866 53857 -9
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- Hits 254047 254004 -43
- Misses 16229 16298 +69
+ Partials 9717 9693 -24
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The arm64 and x86_64 SysV emitters convert each buffer argument with a helper call after loading earlier arguments into their target registers. The call clobbers those registers, so the target would receive wrong values for every argument before the buffer. This is not reachable today: buffer-typed trampolines are generated only for single-argument signatures. Reject other shapes in the emitters so a future caller falls back instead of miscompiling. Signed-off-by: Trivikram Kamat <16024985+trivikr@users.noreply.github.com> Assisted-by: claude:opus-5.5
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The arm64 and x86_64 SysV Fast API emitters convert a
bufferargument by callingnode_ffi_fast_buffer_data(). Arguments before the buffer are already in their target registers at that point, and the call clobbers them. For(i32, buffer)on arm64, the target receives(ptr, ptr).No JS call can reach this today. Buffer-typed trampolines are only generated for single-argument signatures (
SignatureNeedsFastBufferInvoke()), and the primary trampoline rewritesbuffertopointer.This change makes both emitters reject buffer signatures with more than one argument. That matches the only shape generated today, so a future multi-argument caller falls back to another call path instead of getting a broken trampoline. Win64 already rejects buffer arguments.
No test is added because no JS call can reach the rejected signature.
Assisted-by: claude:opus-5.5