[llvm-bugs] [Bug 49708] std::memcpy with incorrect align attribute on arguments introduces undefined behavior
via llvm-bugs
llvm-bugs at lists.llvm.org
Wed Mar 24 02:09:23 PDT 2021
https://bugs.llvm.org/show_bug.cgi?id=49708
Roman Lebedev <lebedev.ri at gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|NEW |RESOLVED
CC| |lebedev.ri at gmail.com
--- Comment #1 from Roman Lebedev <lebedev.ri at gmail.com> ---
Why is that not correct?
A pointer to an integer is 4-byte aligned:
https://clang.godbolt.org/z/zda9M15K1
All accesses to it are 4-byte aligned.
If it is not, that's UB already.
So when `g()` casts a char* to an int*,
iff the target pointer has larger alignment
than the actual alignment of the pointer,
that's UB.
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