From fe0c91cce702525cc26669b382d3d8a234b7e65f Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Sat, 21 Sep 2019 14:35:44 +0100
Subject: [PATCH] configure.in, conffile.fl: Remove dependency on `libfl.a'.

The `libfl' library contains two functions:

  * `main', which basically just calls `yylex' a lot, as an easy way to
    write simple programs in lex(1); and

  * `yywap', which lets a lex(1)-generated lexer know what to do when it
    encounters end-of-file.  Specifically, it can return nonzero to say
    `that's it, we're done', or zero to say `there's more: I've set up
    ``yyin'' so that you can read more stuff'.

The library doesn't do anything very sensible for `yywrap': it just
always returns 1.  (If you wanted to do something more complicated, you
should just write `yywrap' yourself.)

Secnet has its own `main' function which is fine.  It wants `yywrap',
though.  This causes trouble with upstream `flex', which nowadays builds
a shared `libfl.so' library.  This contains /both/ `yywrap' /and/
`main', which breaks the `configure' test: what happens is that the test
program requires `yywrap', which brings in `libfl.so', which brings in
its `main', which refers to an undefined symbol `yylex' that's not
defined in the test program.  This doesn't go wrong in Debian, because
Debian replaces the shared-library `libfl.so' with a linker script which
says `oh, no, you don't want this: you want that ``libfl_pic.a'' over
there'.  The latter is a traditional archive, and ld(1) can pick
`yywrap' out of it without pulling in the bogus `main' and its
dependency on `yylex'.

Anyway, this is all more trouble than it's worth.  Define our own
`yywrap' in `conffile.fl', and delete the `configure' machinery.

Signed-off-by: Mark Wooding <mdw@distorted.org.uk>
---
 conffile.fl  |  3 +++
 config.h.in  |  3 ---
 configure    | 48 ------------------------------------------------
 configure.in |  4 ----
 4 files changed, 3 insertions(+), 55 deletions(-)

diff --git a/conffile.fl b/conffile.fl
index 2ceb01b..77c1e2c 100644
--- a/conffile.fl
+++ b/conffile.fl
@@ -170,3 +170,6 @@ include			BEGIN(incl);
 	/* Return all unclaimed single characters to the parser */
 .			return *yytext;
 
+%%
+
+int yywrap(void) { return 1; }
diff --git a/config.h.in b/config.h.in
index ebd8574..4df92ec 100644
--- a/config.h.in
+++ b/config.h.in
@@ -17,9 +17,6 @@
 /* Define to 1 if you have the `adns' library (-ladns). */
 #undef HAVE_LIBADNS
 
-/* Define to 1 if you have the `fl' library (-lfl). */
-#undef HAVE_LIBFL
-
 /* Define to 1 if you have the `gmp' library (-lgmp). */
 #undef HAVE_LIBGMP
 
diff --git a/configure b/configure
index d98277a..698cc7a 100755
--- a/configure
+++ b/configure
@@ -4486,54 +4486,6 @@ else
 fi
 
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for yywrap in -lfl" >&5
-$as_echo_n "checking for yywrap in -lfl... " >&6; }
-if ${ac_cv_lib_fl_yywrap+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  ac_check_lib_save_LIBS=$LIBS
-LIBS="-lfl  $LIBS"
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-/* Override any GCC internal prototype to avoid an error.
-   Use char because int might match the return type of a GCC
-   builtin and then its argument prototype would still apply.  */
-#ifdef __cplusplus
-extern "C"
-#endif
-char yywrap ();
-int
-main ()
-{
-return yywrap ();
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_lib_fl_yywrap=yes
-else
-  ac_cv_lib_fl_yywrap=no
-fi
-rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext conftest.$ac_ext
-LIBS=$ac_check_lib_save_LIBS
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_fl_yywrap" >&5
-$as_echo "$ac_cv_lib_fl_yywrap" >&6; }
-if test "x$ac_cv_lib_fl_yywrap" = xyes; then :
-  cat >>confdefs.h <<_ACEOF
-#define HAVE_LIBFL 1
-_ACEOF
-
-  LIBS="-lfl $LIBS"
-
-fi
-
-if test "$ac_cv_lib_fl_yywrap" != yes; then
-  as_fn_error $? "A compatible libfl is required" "$LINENO" 5
-fi
 
 
  ac_fn_c_check_func "$LINENO" "inet_ntoa" "ac_cv_func_inet_ntoa"
diff --git a/configure.in b/configure.in
index 2e37df7..ca81407 100644
--- a/configure.in
+++ b/configure.in
@@ -77,10 +77,6 @@ AC_CHECK_LIB(gmp2,mpz_init_set_str)
 AC_CHECK_LIB(gmp,__gmpz_init_set_str)
 REQUIRE_HEADER([gmp.h])
 dnl Would love to barf if no gmp was found, but how to test? Requiring the header will do for now.
-AC_CHECK_LIB(fl,yywrap)
-if test "$ac_cv_lib_fl_yywrap" != yes; then
-  AC_MSG_ERROR([A compatible libfl is required])
-fi
 SECNET_C_GETFUNC(inet_ntoa,nsl)
 AC_CHECK_LIB(socket,socket)
 SECNET_C_GETFUNC(inet_aton,resolv)
-- 
2.11.0