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AC_CHECK_HEADERS_ONCE: honor current AC_LANG

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Previously, AC_CHECK_HEADERS_ONCE collected a list of header names
to check, but ran the checks using the AC_LANG that was active
during the first encounter of the macro.  In practice, this is
usually the C language, and we haven't had actual reports of projects
attempting to use AC_CHECK_HEADERS_ONCE across multiple languages,
rather this was discovered by code inspection.

With this patch, the code now tracks a separate per-language list of
names to check.  Note, however, that it is only possible to check for
a given header name in one language; attempting to add a name again
under AC_CHECK_HEADERS_ONCE while a different language is active is a
no-op (this still makes sense because the side-effect of defining
the CPP macro HAVE_HEADER does not include a language prefix).

* lib/autoconf/headers.m4 (_AC_CHECK_HEADER_ONCE)
(_AC_HEADERS_EXPANSION):
* NEWS: Mention it.

Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Eric Blake 2016-12-21 08:32:29 -06:00
parent 4523f7c32b
commit 501ccbbfdb
2 changed files with 14 additions and 11 deletions
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6
NEWS
View File

@ -111,9 +111,9 @@ GNU Autoconf NEWS - User visible changes.
useful effect is to trigger those checks, with this macro. It is
unlikely to be useful otherwise.
- The AC_CHECK_FUNCS_ONCE macro now supports use with multiple
languages, rather than forcing all checks in the language used by
the first encounter of the macro.
- The AC_CHECK_FUNCS_ONCE and AC_CHECK_HEADERS_ONCE macros now support
use with multiple languages, rather than forcing all checks in the
language used by the first encounter of the macro.
** Man pages for config.guess and config.sub are no longer provided.
They were moved to the master source tree for config.guess and config.sub.

19
lib/autoconf/headers.m4
View File

@ -194,10 +194,10 @@ AC_DEFUN([AC_CHECK_HEADERS],
# Check for a single HEADER-FILE once.
m4_define([_AC_CHECK_HEADER_ONCE],
[_AH_CHECK_HEADER([$1])AC_DEFUN([_AC_Header_]m4_translit([[$1]],
[./-], [___]),
[m4_divert_text([INIT_PREPARE], [AS_VAR_APPEND([ac_header_list], [" $1"])])
_AC_HEADERS_EXPANSION])AC_REQUIRE([_AC_Header_]m4_translit([[$1]],
[./-], [___]))])
[./-], [___]), [m4_divert_text([INIT_PREPARE],
[AS_VAR_APPEND([ac_header_]]_AC_LANG_ABBREV[[_list], [" $1"])])
_AC_HEADERS_EXPANSION(_AC_LANG_ABBREV)])AC_REQUIRE(
[_AC_Header_]m4_translit([[$1]], [./-], [___]))])
# AC_CHECK_HEADERS_ONCE(HEADER-FILE...)
@ -213,11 +213,14 @@ AC_DEFUN([AC_CHECK_HEADERS_ONCE],
AC_DEFUN([_AC_CHECK_HEADERS_ONCE],
[m4_map_args_w([$1], [_AC_CHECK_HEADER_ONCE(], [)])])
# _AC_HEADERS_EXPANSION(LANG)
# ---------------------------
# One-shot code per language LANG for checking all headers registered by
# AC_CHECK_HEADERS_ONCE while that language was active.
m4_define([_AC_HEADERS_EXPANSION],
[m4_divert_text([DEFAULTS], [ac_header_list=])]dnl
[AC_CHECK_HEADERS([$ac_header_list], [], [], [$ac_includes_default])]dnl
[m4_define([_AC_HEADERS_EXPANSION], [])])
[m4_ifndef([$0($1)], [m4_define([$0($1)])m4_divert_text([DEFAULTS],
[ac_header_$1_list=])AC_CHECK_HEADERS([$ac_header_$1_list], [], [],
[$ac_includes_default])])])