Currently, we don't use any Flexisms in scanner.l, we *do* use
%a 18400
%o 21500
%e 7600
%k 4550
%p 27600
%n 2000
to try to boost some of lex's table sizes to handle it, and we make an effort
in the configure file to find regular lex and see if it's capable of processing
scanner.l. There may be some outstanding bugs for lex on some platforms not
being able to handle scanner.l even with those directives.
Using Flex would also let us use this:
https://github.com/the-tcpdump-group/libpcap/pull/359
rather than this:
https://github.com/the-tcpdump-group/libpcap/pull/360
to fix _LARGE_FILES issues on AIX (at the cost of possibly requiring AIX users
to download and install Flex :-)).
We could also at least clean up, if not eliminate, the runlex.sh script.
Flex 2.5.1 (from 1995-03-28) adds %option never-interactive, which avoids
calling isatty() and fileno(), which means we wouldn't have to throw in some
#defines for Windows.
Flex 2.5.6 (from some time in 2002, I think) adds support for reentrant
scanners. This, plus using Bison's or Berkeley YACC's %pure-parser support for
reentrant parsers, could let us make pcap_compile() thread-safe.
Should we continue supporting lex, or should we require Flex? If we require
Flex, should we require 2.5.6 or later, along with Bison or Berkeley YACC, and
make the scanner and parser reentrant?
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