[Mesa-dev] [PATCH] configure.ac: add and use AC_PROG_BISON/FLEX macros

[Kenneth Graunke]

On 01/10/2012 10:16 PM, Matt Turner wrote:
> Defining these macros lets us use AC_PROG_YACC/LEX which makes automake
> easier while still specifically requiring bison and flex.
>
> Based on bison.m4 and flex.m4 found in LLVM's tree.
>
> Signed-off-by: Matt Turner<mattst88 at gmail.com>
> ---
>   configure.ac |    9 ++++-----
>   m4/bison.m4  |   16 ++++++++++++++++
>   m4/flex.m4   |   16 ++++++++++++++++
>   3 files changed, 36 insertions(+), 5 deletions(-)
>   create mode 100644 m4/bison.m4
>   create mode 100644 m4/flex.m4
>
> diff --git a/configure.ac b/configure.ac
> index 511d147..c0abeb9 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -45,11 +45,10 @@ if test "x$MKDEP" = "x"; then
>       AC_MSG_ERROR([makedepend is required to build Mesa])
>   fi
>
> -AC_PATH_PROG([FLEX], [flex])
> -test "x$FLEX" = "x"&&  AC_MSG_ERROR([flex is needed to build Mesa])
> -
> -AC_PATH_PROG([BISON], [bison])
> -test "x$BISON" = "x"&&  AC_MSG_ERROR([bison is needed to build Mesa])
> +m4_include([m4/bison.m4])
> +AC_PROG_BISON
> +m4_include([m4/flex.m4])
> +AC_PROG_FLEX
>
>   dnl Our fallback install-sh is a symlink to minstall. Use the existing
>   dnl configuration in that case.
> diff --git a/m4/bison.m4 b/m4/bison.m4
> new file mode 100644
> index 0000000..641d438
> --- /dev/null
> +++ b/m4/bison.m4
> @@ -0,0 +1,16 @@
> +#
> +# Check for Bison.
> +#
> +# This macro verifies that Bison is installed.  If successful, then
> +# 1) YACC is set to bison -y (to emulate YACC calls)

I don't think we want to emulate POSIX yacc.  We're not using -y today, 
and I expect it'd only break things...

> +# 2) BISON is set to bison
> +#
> +AC_DEFUN([AC_PROG_BISON],
> +[AC_PROG_YACC()
> +if test "$YACC" != "bison -y"; then
> +  AC_SUBST(BISON,[])
> +  AC_MSG_WARN([bison not found])
> +else
> +  AC_SUBST(BISON,[bison])
> +fi
> +])
> diff --git a/m4/flex.m4 b/m4/flex.m4
> new file mode 100644
> index 0000000..6a2a004
> --- /dev/null
> +++ b/m4/flex.m4
> @@ -0,0 +1,16 @@
> +#
> +# Check for FLEX.
> +#
> +# This macro verifies that flex is installed.  If successful, then
> +# 1) LEX is set to flex (to emulate lex calls)
> +# 2) FLEX is set to flex
> +#
> +AC_DEFUN([AC_PROG_FLEX],
> +[AC_PROG_LEX()
> +if test "$LEX" != "flex"; then
> +  AC_SUBST(FLEX,[])
> +  AC_MSG_ERROR([flex not found])
> +else
> +  AC_SUBST(FLEX,[flex])
> +fi
> +])

I like the idea of AC_PROG_FLEX and AC_PROG_BISON macros, but I don't 
care for this implementation.  I would expect them to perform some kind 
of feature check, or ask the program whether it's flex/bison.  This just 
matches on the name, so if I had flex installed only as "lex", or bison 
installed as "bison25" or such, this would break.

Maybe this is okay, but at least in my mind, only allowing one name 
seems to kind of defeat the point of a configure check.  Not entirely, 
but still.