cmc%informatics.rutherford.ac.uk@nss.cs.ucl.ac.uk (03/10/89)
auspex!guy@uunet.uu.net (Guy Harris): >A program that uses "select" "properly" and that is compiled and linked on >a 3.x machine will, assuming no other binary compatibility problems occur, >still work correctly under 4.x under *any* circumstances (modulo bugs in >4.x). In my experience, this assertion that using fd_sets will solve you problems in the case of binary (cf source) compatability is incorrect. I had some trouble with an application failing in select despite using select "properly" with fd_sets as Guy suggests. The problem, of course, is that old fd_sets still only had room for 32 file descriptors which is potentially insufficient for OS4. The fd_sets should have been made large enough to handle the envisaged increase in the number of file descriptors in the first place (corollary of Murphy's law: this is impossible!) Chris. Chris M Crampton JANET: cmc@uk.ac.rl.inf Informatics Department ARPA: cmc%inf.rl.ac.uk@nss.cs.ucl.ac.uk Rutherford Appleton Labs, UUCP: ..!mcvax!ukc!rlinf!cmc Didcot, OXON, OX11 0QX, U.K. cmc@rlinf.uucp Tel. +44 235 44 6756 FAX. +44 235 44 5831 [[ You've got him there...using select "properly" in the way he describes will only work correctly with file descriptor values < 32. However, source level compatability will be maintained. And you should really recompile everything for 4.0 anyway, to take advantage of the shared library (and possibly even the extra levels of compiler optimization). --wnl ]]