convert vector of 4 bytes into int c++

Question

my function read_address always returns a vector of 4 bytes

for other usecases it is a vector and not const array

in this use case I always return 4 bytes

std::vector<uint8_t> content;
 _client->read_address(start_addr, sizeof(int), content);
 uint32_t res = reinterpret_cast<uint32_t>(content.data());
 return res;

here is the vector called content

it is always the same values

however the value of "res" is always changing to random numbers Can you please explain my mistake

Answer 1

Your code is casting the pointer value (random address) to an integer instead of referencing what it points to. Easy fix.

Instead of this:

uint32_t res = reinterpret_cast<uint32_t>(content.data());

This:

uint32_t* ptr = reinterpret_cast<uint32_t*>(content.data());
uint32_t res = *ptr;

The language lawyers may take exception to the above. And because there can be issues with copying data on unaligned boundaries on some platforms. Hence, copying the 4 bytes out of content and into the address of the 32-bit integer may suffice:

memcpy(&res, content.data(), 4);