Hi Russ, sorry for the dealy. On Thursday 19 May 2011, Russ Allbery wrote: > Stefano Lattarini <stefano.lattar...@gmail.com> writes: > > > It seems that AC_PROG_LEX does not diagnose a failure to find the lex > > library required to link lex-generated programs; on the contrary, when > > all the link attempts (i.e., with `-ll' and `-lfl') fail, configure > > uncorrectly declares that no lex library is needed (!), and happily > > proceeds with the configuration process -- only to then have `make' fail > > at build time. This seems wrong to me, and is certainly definitely > > against the autoconf philosophy. > > The current behavior is intentional, I think. See the Autoconf manual's > documentation of AC_PROG_LEX: > > You are encouraged to use Flex in your sources, since it is both > more pleasant to use than plain Lex and the C source it produces > is portable. In order to ensure portability, however, you must > either provide a function `yywrap' or, if you don't use it (e.g., > your scanner has no `#include'-like feature), simply include a > `%noyywrap' statement in the scanner's source. Once this done, > the scanner is portable (unless _you_ felt free to use nonportable > constructs) and does not depend on any library. In this case, and > in this case only, it is suggested that you use this Autoconf > snippet: > > AC_PROG_LEX > if test "x$LEX" != xflex; then > LEX="$SHELL $missing_dir/missing flex" > AC_SUBST([LEX_OUTPUT_ROOT], [lex.yy]) > AC_SUBST([LEXLIB], ['']) > fi > > Autoconf is assuming that people are writing portable scanners and hence > dealing with yywrap, which is why it doesn't require the library exist. > > Thanks for the information. I've now posted a patch on the Automake list that fixes the last spurious failures in the lex tests by making use of your suggestions. Reference: <http://lists.gnu.org/archive/html/automake-patches/2011-05/msg00103.html>
That said, I still think the current autoconf behaviour is somewhat messy and suboptimal, and, if not a real bug, at least an usability issue. But I'm not sure how it could be fixed or improved, so I'll stop complaining for now ;-) Thanks, Stefano
