Compiler Error C2131

expression did not evaluate to a constant

An expression declared as const or constexpr didn't evaluate to a constant at compile time. The compiler must be able to determine the value of the expression at the point it's used.

Example

This example shows a way to cause error C2131, and how to fix it.

// c2131.cpp
// compile by using: cl /EHsc /W4 /c c2131.cpp

struct test
{
    static const int array_size; // To fix, init array_size here.
    int size_array[array_size];  // C2131
};

const int test::array_size = 42;

c2131.cpp
c2131.cpp(7): error C2131: expression did not evaluate to a constant
c2131.cpp(7): note: failure was caused by non-constant arguments or reference to a non-constant symbol
c2131.cpp(7): note: see usage of 'array_size'

See also

const
constexpr