There’s an assumption in URL::FallbackDownloadTask::run that content won’t be larger than std::numeric_limits<int64>::max():
auto max = jmin ((int) bufferSize, contentLength < 0 ? std::numeric_limits<int>::max()
: static_cast<int> (contentLength - downloaded));
If contentLength is bigger than std::numeric_limits<int>::max() then the static cast can UB/overflow to a negative number and max gets assigned a negative.
I think changing it to support int64 will work, that way it can’t overflow and because bufferSize is always small, max will always be positive:
auto max = (int) jmin ((int64) bufferSize, contentLength < 0 ? std::numeric_limits<int64>::max()
: static_cast<int64> (contentLength - downloaded));
Would you be able to make that change?
