Overflow risk?

[ykempf]

Correct me if I am wrong, but if the buffer size is set to the maximum of 2G, then this line will overflow and misbehave if the buffer is just below the limit and if bufferTop + size exceeds 2G, as all of these are int.
https://github.com/fmihpc/vlsv/blob/master/vlsv_writer.cpp#L788

Isn't it?

[markusbattarbee]

Looks like it to me.

[sandroos]

you are correct

[ursg]

I guess the easiest fix for this would be an explicit 64bit unsigned comparison in that spot:
42cb9fa

[ykempf]

The remaining question is, are there more similar bugs lurking?

[sandroos]

Dunno, this is the new code from frroberts. Looking at this code again I don't think it works at all if the buffer gets filled up. If bufferSize is exceeded then buffer needs to be flushed to disk before the new data can be added, but this is not done.

I have to edit my previous comment a little bit: technically the original code works, MPI can only write getMaxBytesPerRead() bytes in a single collective, and that is less than INT_MAX.