compiler-warning-level-4-c4457.md

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Learn more about: Compiler Warning (level 4) C4457	Compiler Warning (level 4) C4457	11/04/2016	C4457	C4457	02fd149a-917d-4f67-97a6-eb714572271f

Compiler Warning (level 4) C4457

declaration of 'identifier' hides function parameter

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

Example

The following sample generates C4457 because the parameter x and the local variable x in member_fn have the same names. To fix this issue, use different names for the parameters and local variables.

// C4457_hide.cpp
// compile with: cl /W4 /c C4457_hide.cpp

struct S {
    void member_fn(unsigned x) {
        double a = 0;
        for (int x = 0; x < 10; ++x) {  // C4457
            a += x; // uses local x
        }
        a += x; // uses parameter x
    }
} s;