Paolo Bonzini <bonzini <at> gnu.org> writes:
First thought, before I even begin a thorough review:
> # AC_CHECK_FUNC(FUNCTION, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
> # -----------------------------------------------------------------
> AC_DEFUN([AC_CHECK_FUNC],
> -[AS_VAR_PUSHDEF([ac_var], [ac_cv_func_$1])dnl
> -AC_CACHE_CHECK([for $1], [ac_var],
> -[AC_LINK_IFELSE([AC_LANG_FUNC_LINK_TRY([$1])],
> - [AS_VAR_SET([ac_var], [yes])],
> - [AS_VAR_SET([ac_var], [no])])])
> +[AS_REQUIRE_SHELL_FN([ac_func_]_AC_LANG_ABBREV[_check_func], [
> + AS_LINENO_PUSH([$[]1])
> + AS_VAR_PUSHDEF([ac_var], [ac_cv_func_$[]2])dnl
> + AC_CACHE_CHECK([for $[]2], [ac_var],
> + [AC_LINK_IFELSE([AC_LANG_FUNC_LINK_TRY([$][2])],
> + [AS_VAR_SET([ac_var], [yes])],
> + [AS_VAR_SET([ac_var], [no])])])
> + AS_VAR_POPDEF([ac_var])dnl
> + AS_LINENO_POP
> +])dnl
> +ac_func_[]_AC_LANG_ABBREV[]_check_func "$LINENO" "$1"
> +AS_VAR_PUSHDEF([ac_var], [ac_cv_func_$1])dnl
> AS_VAR_IF([ac_var], [yes], [$2], [$3])dnl
> AS_VAR_POPDEF([ac_var])dnl
> ])# AC_CHECK_FUNC
This is getting slightly hard to review without shell comments describing how a
function is to be used (for example, AS_LINENO_PUSH([$[]1]) as the first line
of the function body means that the function expects $LINENO as its first
argument, but that isn't commented anywhere other than by examining how the
function is called); this means that the function appears in the configure file
with no comments whatsoever. I propose that we modify AS_REQUIRE_SHELL_FN as
follows:
# AS_REQUIRE_SHELL_FN(name, [comment], body, [diversion])
# --------
m4_define(...)
And define a helper function:
# AS_FUNCTION_DESCRIBE(name, [args], description)
# -----------------------------------------------
# Output a shell comment that looks like:
# # NAME ARGS
# # ---------
# # DESCRIPTION
# where the second line sizes itself according to the first, and where
# DESCRIPTION is treated as a whitespace separated list of words
# to be wrapped at 76 columns.
m4_define(...)
[I can help with the m4sugar magic needed here, if you like the idea; borrowing
from AS_HELP_STRING]
Then back to a concern I raised earlier - time spent parsing complex shell
functions listed early in the script makes 'configure --help' that much
slower. I'd like reserve M4SH-INIT-FN for as_func_*, and see all ac_func_*
dumped in a different diversion (for argument sake, let's call it AC_INIT_FN,
and that it is between VERSION_END and INIT_PREPARE). So, to efficiently
output functions into this diversion (and to use my above idea of outputting
shell comments), I would add this wrapper at the autoconf level:
# AC_REQUIRE_SHELL_FN(name, [args], description, body)
# ----------------------------------------------------
# Ensure that function ac_func_NAME that takes arguments ARGS is defined,
# with comments DESCRIPTION and contents BODY, and is emitted prior to
# anyone who wants to call the function, but after --help is handled.
m4_define([AC_REQUIRE_SHELL_FN],
[AS_REQUIRE_SHELL_FN([ac_func_$1],
[AS_FUNCTION_DESCRIBE([ac_func_$1], [$2], [$3])],
[$4], [AC_INIT_FN])])
With the wrapper in place, the above code could be written:
AC_REQUIRE_SHELL_FN(_AC_LANG_ABBREV[_check_func], [line name],
[Check whether it is possible to link against the ]_AC_LANG_ABBREV[
function NAME, and log the result with a message that includes LINE
as its point of origin.], [
AS_LINENO_PUSH([$[]1])
AS_VAR_PUSHDEF([ac_var], [ac_cv_func_$[]2])dnl
...])
ac_func_[]_AC_LANG_ABBREV[]_check_func $LINENO "$1"
and the configure file after AC_CHECK_FUNC([cos]) would look like:
[in AC_INIT_FN]
# ac_func_C_check_func line name
# ------------------------------
# Check whether it is possible to link against the C function NAME, and
# log the result with a message that includes LINE as its point of
# origin.
ac_func_C_check_func () {
as_lineno=${as_lineno-"$1"}...
}
[much later, in BODY]
ac_func_C_check_func $LINENO "cos"
What do you think?
--
Eric Blake
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