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There might even be some builtin support for this check in autoconf as the issue is mentioned in [1].

I looked a bit yesterday and didn't get the impression that there was anything.

There is an autoconf m4 macro for snprintf, with some IRIX specific checks, here: http://www.jhweiss.de/software/snprintf.html According to that page versions of IRIX all the way up to the present (6.5.30) don't adhere to the standard. For what it's worth this is the IRIX online manual page for snprintf(): http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?coll=0650&db=man&fnam...