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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/61656] New: Undefined behavior in classify_argument Date: Mon, 30 Jun 2014 11:05:00 -0000 [thread overview] Message-ID: <bug-61656-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61656 Bug ID: 61656 Summary: Undefined behavior in classify_argument Product: gcc Version: 4.10.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: jakub at gcc dot gnu.org CC: hjl.tools at gmail dot com, hubicka at gcc dot gnu.org, uros at gcc dot gnu.org Target: x86_64-linux /usr/src/gcc/obj052/gcc/xgcc -B/usr/src/gcc/obj052/gcc/ -fno-diagnostics-show-caret -fdiagnostics-color=never -O0 -w -c -o pr4 2025-2.o /usr/src/gcc/gcc/testsuite/gcc.c-torture/compile/pr42025-2.c ../../gcc/config/i386/i386.c:6583:60: runtime error: mload of value 32669, which is not a valid value for type 'x86_64_reg_class' This is on passing typedef struct { void *p; } Ptr; struct A { int i; union { Ptr p; char *q; } u; }; by value and the problem is that when processing the union with bit_offset 64, words is 1 (u is DImode 64-bit field), but when we recurse, we are called with 64-bit scalar DImode q and bit_offset 64, that is size (128-1)&0x7f and so it is the size < 64+64 case where we return 2 and { X86_64_INTEGER_CLASS, X86_64_INTEGER_CLASS }; in subclauses. But words is 1 and we merge classes up to num (2). A simple fix could be: if (!num) return 0; - for (i = 0; i < num; i++) + for (i = 0; i < num && i < words; i++) classes[i] = merge_classes (subclasses[i], classes[i]); in the UNION_TYPE case, as it seems the caller will not care about classes above returned number (words). I'd hope such a patch should not change the ABI even. I don't know whether there isn't an ABI problem related to this though, say if at bit_offset 64 we have just SImode field in the union rather than DImode, then I'd guess the recursive call would give us { X86_64_INTEGER_CLASS, X86_64_INTEGERSI_CLASS }; but we'd use X86_64_INTEGER_CLASS anyway, as we are looking at position 0, not 1.
next reply other threads:[~2014-06-30 11:05 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-06-30 11:05 jakub at gcc dot gnu.org [this message] 2014-07-04 12:02 ` [Bug target/61656] " ubizjak at gmail dot com 2014-07-10 15:33 ` ubizjak at gmail dot com 2014-07-10 16:10 ` ubizjak at gmail dot com 2014-07-14 7:32 ` jakub at gcc dot gnu.org 2014-07-20 22:24 ` jakub at gcc dot gnu.org 2014-07-25 6:11 ` pinskia at gcc dot gnu.org 2014-07-25 7:48 ` uros at gcc dot gnu.org 2014-07-25 7:49 ` ubizjak at gmail dot com
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