compiler-warning-level-4-c4456.md

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Learn more about: Compiler Warning (level 4) C4456	Compiler Warning (level 4) C4456	11/04/2016	C4456	C4456	5ab39fc1-0e19-461b-842b-4da80560b044

Compiler Warning (level 4) C4456

declaration of 'identifier' hides previous local declaration

The declaration of identifier in the local scope hides the declaration of the previous local declaration of the same name. This warning lets you know that references to identifier in the local scope resolve to the locally declared version, not the previous local, which may or may not be your intent. To fix this issue, we recommend you give local variables names that do not conflict with other local names.

Example

The following sample generates C4456 because the loop control variable int x and the local variable double x in member_fn have the same names. To fix this issue, use different names for the local variables.

// C4456_hide.cpp
// compile with: cl /W4 /c C4456_hide.cpp

struct S {
    void member_fn(unsigned u) {
        double x = 0;
        for (int x = 0; x < 10; ++x) {  // C4456
            u += x; // uses local int x
        }
        x += u; // uses local double x
    }
} s;