> `configure` should warn or bail on incompatible flex versions. I
> suggest we add a version check in configure.ac to ensure that flex
> version is between 2.5.37 and 2.5.39 (given that 2.5.38 and 2.5.39
> actually works).
What you suggest wouldn't work as expected. There is no guarantee
that `FlexLexer.h` found during compilation is the one that is used by
a recent flex version. Unfortunately, `FlexLexer.h` doesn't contain
any version information, so it is really impossible to protect against
this situation automatically.
I was bitten by that on my Mac OS Lion box, and as a consequence I
implemented the `--with-flexlexer-dir` configuration option.
Werner
