how to correctly cast uint32_t to unsigned

Question

I'm trying to fix some C++ code with address sanitizer. The code says:

unsigned result = *(uint32_t*)data;

And the sanitizer gives:

runtime error: load of misaligned address 0x6280033f410a for type 'uint32_t', which requires 4 byte alignment

How do I need to fix this?

`memcpy` the pointer to a real `uint32_t`, before casting it to `unsigned`. — Sam Varshavchik, Sep 14 '17 at 21:47
The question is apparently not about "how to cast". And it seems to have nothing to do with "cast to `unsigned`". The question is rather about how to read misaligned data. So, please confirm: do you really intend to read misaligned data? Is it supposed to be misaligned? Why is it misaligned and how did it end up that way? — AnT stands with Russia, Sep 14 '17 at 22:28
Without any feedback from OP this question isn't very useful. — Galik, Sep 14 '17 at 22:33

eerorika · Accepted Answer · 2017-09-14T22:33:05.917

0

load of misaligned address 0x6280033f410a for type 'uint32_t' ...

How do I need to fix this?

You need to create an aligned object (such as a variable), and copy the content from the misaligned address:

std::uint32_t u32;
std::memcpy(&u32, data, sizeof u32);

This assumes that you intend to read sizeof u32 bytes from that address and that those bytes are ordered in native endianness.

how to correctly cast uint32_t to unsigned

Implicit conversion should be just fine:

unsigned result = u32;

edited Sep 14 '17 at 22:33

answered Sep 14 '17 at 22:26

eerorika

many thanks, `std::uint32_t u32; std::memcpy(&u32, data, sizeof u32);` fixed the issue! – Jan 02 '18 at 17:10

1 Answers1