clang-tidy - misc-misplaced-widening-cast — Extra Clang Tools 3.9 documentation

# Extra Clang Tools 3.9 documentation

## clang-tidy - misc-misplaced-widening-cast

# misc-misplaced-widening-cast

This check will warn when there is a cast of a calculation result to a bigger type. If the intention of the cast is to avoid loss of precision then the cast is misplaced, and there can be loss of precision. Otherwise the cast is ineffective.

Example code:

    long f(int x) {
        return (long)(x*1000);
    }

The result x*1000 is first calculated using int precision. If the result exceeds int precision there is loss of precision. Then the result is casted to long.

If there is no loss of precision then the cast can be removed or you can explicitly cast to int instead.

If you want to avoid loss of precision then put the cast in a proper location, for instance:

    long f(int x) {
        return (long)x * 1000;
    }

## Implicit casts

Forgetting to place the cast at all is at least as dangerous and at least as common as misplacing it. If option `CheckImplicitCasts` is enabled (default) the checker also detects these cases, for instance:

    long f(int x) {
        return x * 1000;
    }

## Floating point

Currently warnings are only written for integer conversion. No warning is written for this code:

    double f(float x) {
        return (double)(x * 10.0f);
    }