./configure should fail if (f)lex tests fail

[physicalist]

GENESIS needs flex/lex to be installed and work properly, and the library has to be linkable.
Currently, on a system where flex is installed but the library can't be found–both -lfl nor -ll lead to a linking error like /usr/bin/ld: cannot find -lfl–the configure script still doesn't fail, but instead concludes checking lex library... none needed, and moves on.
Compilation will subsequently fail due to non-generated intermediate files.

Instead, ./configure should already fail if no lex library is found.

[borismarin]

https://lists.gnu.org/archive/html/bug-autoconf/2011-05/msg00017.html

[physicalist]

Hm I didn't see that in my previous search, thanks for the link. So it seems to be a 4-years old bug in autoconf. Still looks like this in my local 2.69 installation (OSX/Homebrew)
I'll see if I can work around this in the configure script when I find the time.

[dbeeman]

Thanks for reporting that. I have always had the flex libraries installed in the usual path, and never encountered this problem. Fortunately, the installation README tells how to find and install flex, so I hope this won't be much of a problem. If you get around to making a fix, I'd like to put it in the official github repo for continued GENESIS 2.4 development. This is at https://github.com/genesis-sim/genesis-2.4.

[borismarin]

A workaround had even been implemented https://github.com/borismarin/genesis2.4gamma/blob/master/src/ss/yyless.c