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What You Can Learn from Compiler Warnings

What You Can Learn from Compiler Warnings

The following code has a subtle bug. Can you detect it?

 DWORD ErrCode = GetLastError(); // Retrieve the error codeif (!ErrCode==ERROR_FILE_NOT_FOUND) // warning on this line

Although the compiler cannot guess the programmer’s intent, it issues a warning message that provides a cue:

 warning C4806: '==' : unsafe operation: no value of type 'bool'

 promoted to type 'const long' can equal the given constant.

The compiler says it cannot safely compare a variable of type bool and const long. Wait a minute

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