CODEWITHSUNDEEP
c++pointerslambdacapture
user5406764
user5406764

Reputation: 1795

Lambda capture (by value) of array is only copying the pointer?

I'm trying to capture (by value) an entire C-style array. The array seems to decay to a pointer... How do I prevent this so that the whole array is captured?

Code:

#include <iostream>

int main()
{
    char x[1024];

    std::cerr << sizeof(x) << "\n";
    [x = x] // copy
    {
        std::cerr << sizeof(x) << "\n";
    }();
}

This prints:

1024  <<-- yay
8     <<-- oops... not a true copy

It should be noted that this works as I had hoped (1024 for both results):


#include <iostream>
#include <array>

int main()
{
    std::array<char, 1024> x;

    std::cerr << sizeof(x) << "\n";
    [x = x] // copy
    {
        std::cerr << sizeof(x) << "\n";
    }();
}

Upvotes: 6

Views: 793

Answers (1)

jdfa
jdfa

Reputation: 699

[x = x]

This one is equal to

auto x1 = x;

Which is actually decay to a pointer.

Just change your lambda capture to [x] to capture x by value. Also you can capture it by reference with [&x].

Upvotes: 7

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