I was trying to reproduce Tom's and Paul's problem (isnan), when I encountered a problem with Flex: it should not be required, yet the build fails without.
So far, I am still unable to reproduce the isnan problem (I tried a fedora distro in Docker). commit 825150b08505ed83fd7257f671fb1889aa41a0e6 Author: Akim Demaille <[email protected]> Date: Tue Oct 8 08:34:13 2019 +0200 configure: don't require Flex Flex should not be required to build Bison or run the test suite (of course it is needed for maintaining Bison). Yet the Automake conditional FLEX_WORKS does not work. * m4/flex.m4 (_AC_PROG_LEX_YYTEXT_DECL): Since this is called conditionally, don't define LEX_IS_FLEX here, but rather... (AC_PROG_LEX): here. * configure.ac: Be more cautious about possibly undefined variables. diff --git a/configure.ac b/configure.ac index 38d64609..90320fb7 100644 --- a/configure.ac +++ b/configure.ac @@ -211,10 +211,10 @@ AC_CONFIG_FILES([src/yacc], [chmod +x src/yacc]) # Checks for programs. AM_MISSING_PROG([DOT], [dot]) AC_PROG_LEX -$LEX_IS_FLEX || test "X$LEX" = X: || { +if ! "$LEX_IS_FLEX" || test "X$LEX" = X:; then AC_MSG_WARN([bypassing lex because flex is required]) LEX=: -} +fi AM_CONDITIONAL([FLEX_WORKS], [$LEX_IS_FLEX]) AM_CONDITIONAL([FLEX_CXX_WORKS], [$LEX_IS_FLEX && test $bison_cv_cxx_works = yes]) diff --git a/m4/flex.m4 b/m4/flex.m4 index 70cea7d3..ed230a2a 100644 --- a/m4/flex.m4 +++ b/m4/flex.m4 @@ -15,7 +15,10 @@ AC_DEFUN_ONCE([AC_PROG_LEX], [AC_CHECK_PROGS([LEX], [flex lex], [:]) if test "x$LEX" != "x:"; then _AC_PROG_LEX_YYTEXT_DECL -fi]) +fi +AC_SUBST([LEX_IS_FLEX], + [`test "$ac_cv_prog_lex_is_flex" = yes && echo true || echo false`])dnl +]) # _AC_PROG_LEX_YYTEXT_DECL @@ -37,8 +40,6 @@ else ac_cv_prog_lex_is_flex=no fi ]) -AC_SUBST([LEX_IS_FLEX], - [`test "$ac_cv_prog_lex_is_flex" = yes && echo true || echo false`])dnl cat >conftest.l <<_ACEOF[ %%
