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* [Bug c++/111742] New: Misaligned generated code with MI using aligned virtual base @ 2023-10-09 17:19 cuzdav at gmail dot com 2023-10-09 17:28 ` [Bug c++/111742] " pinskia at gcc dot gnu.org ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: cuzdav at gmail dot com @ 2023-10-09 17:19 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111742 Bug ID: 111742 Summary: Misaligned generated code with MI using aligned virtual base Product: gcc Version: 13.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: cuzdav at gmail dot com Target Milestone: --- Generated code is misaligned (and crashes in slightly more complex code), in trunk all the way back to gcc 8.1, when built in c++11 or higher, with O3. (Linux, x86) Complete code: ////////////////////////////////////////// struct X { void * a = nullptr; void * b = nullptr; }; struct alignas(16) AlignedData { }; struct A : virtual AlignedData { X xxx; }; struct B : virtual AlignedData {}; struct Test : B, A {}; Test* t = new Test; int main() {} ////////////////////////////////////////// Compiler Explorer demo: https://godbolt.org/z/aodTdaedW Running with UB-san reports this: /app/example.cpp:14:8: runtime error: constructor call on misaligned address 0x00000227f2b8 for type 'struct A', which requires 16 byte alignment 0x00000227f2b8: note: pointer points here 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ^ /app/example.cpp:8:8: runtime error: member access within misaligned address 0x00000227f2b8 for type 'struct A', which requires 16 byte alignment 0x00000227f2b8: note: pointer points here 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ^ ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/111742] Misaligned generated code with MI using aligned virtual base 2023-10-09 17:19 [Bug c++/111742] New: Misaligned generated code with MI using aligned virtual base cuzdav at gmail dot com @ 2023-10-09 17:28 ` pinskia at gcc dot gnu.org 2023-10-09 17:50 ` cuzdav at gmail dot com 2023-10-09 17:51 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-10-09 17:28 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111742 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |DUPLICATE --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- It is just a santizer issue. Dup of bug 83780. *** This bug has been marked as a duplicate of bug 83780 *** ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/111742] Misaligned generated code with MI using aligned virtual base 2023-10-09 17:19 [Bug c++/111742] New: Misaligned generated code with MI using aligned virtual base cuzdav at gmail dot com 2023-10-09 17:28 ` [Bug c++/111742] " pinskia at gcc dot gnu.org @ 2023-10-09 17:50 ` cuzdav at gmail dot com 2023-10-09 17:51 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: cuzdav at gmail dot com @ 2023-10-09 17:50 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111742 --- Comment #2 from Chris Uzdavinis <cuzdav at gmail dot com> --- No, this is not a ubsan report. Code *crashes* and I thought showing the UBsan warning was enough to demonstrate it. A minimal change to make the code crash instead of just report ubsan errors: struct X { void * a = nullptr; void * b = nullptr; }; struct alignas(16) AlignedData { }; struct A : virtual AlignedData { int x = 0; // << ********add this X xxx; int& ref = x; // << ********and this }; struct B : virtual AlignedData {}; struct Test : B, A {}; Test* t = new Test; int main() {} *** SEGFAULT *** https://godbolt.org/z/f57vs7jxP ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/111742] Misaligned generated code with MI using aligned virtual base 2023-10-09 17:19 [Bug c++/111742] New: Misaligned generated code with MI using aligned virtual base cuzdav at gmail dot com 2023-10-09 17:28 ` [Bug c++/111742] " pinskia at gcc dot gnu.org 2023-10-09 17:50 ` cuzdav at gmail dot com @ 2023-10-09 17:51 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-10-09 17:51 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111742 --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Then it is a dup of bug 71644. *** This bug has been marked as a duplicate of bug 71644 *** ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2023-10-09 17:51 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-10-09 17:19 [Bug c++/111742] New: Misaligned generated code with MI using aligned virtual base cuzdav at gmail dot com 2023-10-09 17:28 ` [Bug c++/111742] " pinskia at gcc dot gnu.org 2023-10-09 17:50 ` cuzdav at gmail dot com 2023-10-09 17:51 ` pinskia at gcc dot gnu.org
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