On 31/10/2016 18:01, Eric Blake wrote: > On 10/31/2016 10:33 AM, Paolo Bonzini wrote: >> >> >> On 31/10/2016 16:28, Eric Blake wrote: >>> On 10/31/2016 06:39 AM, Paolo Bonzini wrote: >>>> An unrolled loop avoids the cost of spawning sed in AS_TR_SH and >>>> AS_TR_CPP. Prefer it if there is nothing in the second and third >>>> argument of AC_CHECK_FUNCS and the first argument is a literal. >>>> Modify AC_CHECK_FUNCS_ONCE to avoid the variable indirection too. >>>> >>>> * lib/autoconf/functions.m4 (AC_CHECK_FUNCS): Unroll loop if safe. >>>> (_AC_CHECK_FUNCS): Move basic implementation here. >>>> (_AC_CHECK_FUNC_ONCE): Expand AC_CHECK_FUNCS here... >>>> (_AC_FUNCS_EXPANSION): ... and not here, so remove. >>> >>>> - [$3])dnl]) >>>> +[m4_if([$2$3]AS_LITERAL_IF([$1], [yes], [no]), []yes, >>> >>> Why []yes instead of the more typical [yes] ? >>> >>> If the user has (unwisely) defined yes as a macro, your version will >>> compare against their expansion, instead of against the intended literal. >> >> Because I've never understood the rules for m4_if, and thought []yes >> matched what you get from m4_if([$2$3]AS_LITERAL_IF([$1], [yes], [no]). > > If 'yes' and 'no' are not macros, then these are identical: > > m4_if([$2$3]AS_LITERAL_IF([$1], yes, no), yes, ...) > m4_if([$2$3]AS_LITERAL_IF([$1], [yes], [no]), []yes[], ...) > m4_if([$2$3]AS_LITERAL_IF([$1], [[yes]], [[no]]), [yes], ...) > > because of the order in which quotes are stripped through successive > levels of m4 processing. But if yes or no could be a macro, then only > the latter form is safe against unintended expansions (yes, including > the double-quoting within AS_LITERAL_IF, because one layer of quotes > gets stripped when collecting the args to AS_LITERAL_IF, and another > gets stripped when concatenating to [$2$3] to determine the final string > to compare against the literal of the second argument to m4_if).
Good, this is what I wanted. I'll send v2 where the
only difference will be:
diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4
index 1043192..ccfb053 100644
--- a/lib/autoconf/functions.m4
+++ b/lib/autoconf/functions.m4
@@ -85,7 +85,7 @@ m4_define([_AH_CHECK_FUNC],
# `break' to stop the search.
AC_DEFUN([AC_CHECK_FUNCS],
[m4_map_args_w([$1], [_AH_CHECK_FUNC(], [)])]dnl
-[m4_if([$2$3]AS_LITERAL_IF([$1], [yes], [no]), []yes,
+[m4_if([$2$3]AS_LITERAL_IF([$1], [[yes]], [[no]]), [yes],
[m4_map_args_w([$1], [_$0(], [)])],
[AS_FOR([AC_func], [ac_func], [$1], [_$0(AC_func, [$2], [$3])])])
])# AC_CHECK_FUNCS
diff --git a/lib/autoconf/headers.m4 b/lib/autoconf/headers.m4
index e855025..42f373f 100644
--- a/lib/autoconf/headers.m4
+++ b/lib/autoconf/headers.m4
@@ -182,7 +182,7 @@ m4_define([AH_CHECK_HEADERS],
# header. Either ACTION may include `break' to stop the search.
AC_DEFUN([AC_CHECK_HEADERS],
[m4_map_args_w([$1], [_AH_CHECK_HEADER(], [)])]dnl
-[m4_if([$2$3]AS_LITERAL_IF([$1], [yes], [no]), []yes,
+[m4_if([$2$3]AS_LITERAL_IF([$1], [[yes]], [[no]]), [yes],
[m4_map_args_w([$1], [_$0(], [, [], [], [$4])])],
[AS_FOR([AC_header], [ac_header], [$1], [_$0(AC_header, [$2], [$3],
[$4])])])
])# AC_CHECK_HEADERS
Please commit for me, since I don't have write access to autoconf.git.
Thanks,
Paolo
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