[llvm-bugs] [Bug 49708] std::memcpy with incorrect align attribute on arguments introduces undefined behavior

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49708

Gonzalo BG <gonzalo.gadeschi at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|INVALID                     |---

--- Comment #2 from Gonzalo BG <gonzalo.gadeschi at gmail.com> ---
I hope this makes it clearer. The above example is equivalent to:

char h(char* ptr) { 
    ptr = (char*)(int*)ptr;
    return *ptr;
}

> A pointer to an integer is 4-byte aligned:

A load through a pointer to an integer can assume 4-byte alignment.

In the functions f, g, and h that I've shown, there are no such loads anywhere.

h loads through a char*, and f loads through an unsigned char* inside
std::memcpy according to the memcpy spec.

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