tidy - bugprone-fold-init-type — Extra Clang Tools 22.0.0git documentation (original) (raw)
The check flags type mismatches infoldslike std::accumulate that might result in loss of precision.std::accumulate folds an input range into an initial value using the type of the latter, with operator+ by default. This can cause loss of precision through:
- Truncation: The following code uses a floating point range and an int initial value, so truncation will happen at every application of
operator+and the result will be 0, which might not be what the user expected.
auto a = {0.5f, 0.5f, 0.5f, 0.5f}; return std::accumulate(std::begin(a), std::end(a), 0);
- Overflow: The following code also returns 0.
auto a = {65536LL * 65536 * 65536}; return std::accumulate(std::begin(a), std::end(a), 0);