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Cheers, Jean-Claude Beaudoin ---------- Forwarded message ---------- From: Jean-Claude Beaudoin <jean.claude.beaud...@gmail.com> Date: Wed, Mar 25, 2009 at 1:13 AM Subject: CFFI should defend itself against fragile handling of narrow return types in SBCL on x86! To: cffi-devel@common-lisp.net Recent versions of GCC appear to be leaving spurious bits in the %eax register used to return the value of a C function on x86 based platforms when the return type is narrower than 32 bits (ie: short or char). SBCL does not defend itself against such register pollution and will return an incorrect value made up of those spurious bits in addition to the intended value. A partial fix for "signed" short and char has appeared in SBCL 1.0.25 but the "unsigned" cases are still vulnerable. I suggest that CFFI should defend itself against that dangerously permissive handling of narrow return types in SBCL through the use of a few filtering functions to be applied in those relevant cases, at least until SBCL fixes the issue for good. Here is attached a patch against CFFI 0.10.4 with a version of the required code. I also attach a set of test files that can be used to illustrate the problem. Cheers, Jean-Claude Beaudoin
cffi_0.10.4_sbcl_strict_widening.patch
Description: Binary data
widening.tar.gz
Description: GNU Zip compressed data
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