Visual C ++ Warning C4800, why does it only start with return statements?

Question

I just installed the Windows SDK v7.1 (MSVC 10.0) and executed my code through the (almost) full warning level (W3, the default for qmake CONFIG += warn_on) and was surprised by the warningC4800: 'type' : forcing value to bool 'true' or 'false' (performance warning)

The following code streamis std::istream, but token- std::string.

// in some function returning bool
return (stream >> token) // triggers warning c4800:
                         // '(void *)': forcing value to bool 'true' or 'false' (performance warning)`
// somewhere else
if( stream >> token ) // does not trigger warning c4800

What's going on here? I don’t even understand why the warning is triggered in the first place. I thought the first bit of code already returned bool.

I understand that this is nitpicking and the warning should not exist, but it is the only one in my code between MSVC /W3and gcc -Wall -pedantic, so I would like to know :)

SMALL UPDATE: I understand that the warning is designed so that you know that you accept int-> bool conversion, but 1) why you will still use bool (== typedef intbasically) and 2) why if(2)not convert 2to true or false, I thought it was the whole predicate idea that is true or false.

Answer 1

What's going on here? I don’t even understand why the warning is triggered in the first place. I thought the first bit of code already returned bool.

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Answer 2

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Answer 3

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