This issue came up on the MacPascal list, but since I recently ran across an RTS thread safety issue, I thought I'd post it here too, at least for reference if not for anything else.

There is a multi-platform multi-threading unit for gpc, see <http://www.gnu-pascal.de/crystal/gpc/en/mail10658.html> (but also read <http://www.gnu-pascal.de/crystal/gpc/en/thread10512.html>).

One thing I didn't see mentioned in the thread, but I discovered recently is that the routines like ReadStr/WriteStr are not thread safe. In particular they use a global variable (LastReadWriteStrFDR) for the file handle internally (to avoid re-allocating it each time), which is not MP thread safe. Also, they use an IOResult global variable (InOutRes variable). To properly handle MP threading, the RTS would, at the least, require everything to have a returned error result, rather than using IOResult, which would be a big change (although this would be desirable for New as well). This change would be incompatible with existing RTS routines, although it could possible be accomplished by placing a thread safe layer underneath the thread-unsafe standard RTS API, for example (very loose pseudo code) : procedure WriteStr( xxx ) var error: yyy; begin fh := GetReadWriteStrFDR; error := WriteStrSafe( fh, xxx ) InOutRes := error; conditionally exit with a runtime error end; It would also likely require additions/changes to the way the compiler interacted with the RTS. Any way you slice it, it'd be a fair amount of work to be entirely thread safe. Enjoy, Peter. -- <http://www.stairways.com/> <http://download.stairways.com/>