[SCM] GNU Autoconf source repository branch, master, updated. v2.69-171-g527f183

[Eric Blake]

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- Log -----------------------------------------------------------------
commit 527f183f232e14ebf0ef2b8a086d675e78700af2
Author: Paolo Bonzini <address@hidden>
Date:   Mon Oct 31 18:08:08 2016 +0100

    autoconf: refine quadrigraph test in _AC_DEFINE_UNQUOTED
    
    It is a very common case that a quadrigraph appears in the argument of
    _AC_DEFINE_UNQUOTED, because "#define" is expanded through a quadrigraph.
    Therefore, restrict the quadrigraph tests to "$" (for "$(" and "${")
    and "(" (for "$(").
    
    At the same time, "#" should not be used inside AC_ECHO because it confuses
    m4's comment parsing.  This pre-existing latent bug is caught by test 251:
    
       AC_DEFINE_UNQUOTED([bar], [[%!_!# X]])
    
    Previously the quadrigraph in "@%:@define bar %!_!# X" made Autoconf fall 
back
    to cat anyway.  Now that Autoconf is not fooled by the quadrigraph, the test
    catches that "#" is not special-cased.  Kudos to Eric for coming up with it!
    
    * lib/autoconf/general (_AC_DEFINE_UNQUOTED): Do not blindly
    use cat on all quadrigraphs.
    
    Signed-off-by: Paolo Bonzini <address@hidden>
    Message-Id: <address@hidden>

-----------------------------------------------------------------------

Summary of changes:
 lib/autoconf/general.m4 |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/autoconf/general.m4 b/lib/autoconf/general.m4
index c15fb13..ef6285d 100644
--- a/lib/autoconf/general.m4
+++ b/lib/autoconf/general.m4
@@ -2167,9 +2167,11 @@ m4_define([AC_DEFINE_UNQUOTED], [_AC_DEFINE_Q([_$0], 
$@)])
 # Append the pre-expanded STRING and a newline to confdefs.h, as if
 # with an unquoted here-doc, but avoiding a fork in the common case of
 # no backslash, no command substitution, no complex variable
-# substitution, and no quadrigraphs.
+# substitution (taking into account quadrigraphs as well).  Also
+# avoid AS_ECHO if "#" is present to avoid confusing m4 with comments,
+# but quadrigraphs are fine in that case.
 m4_define([_AC_DEFINE_UNQUOTED],
-[m4_if(m4_bregexp([$1], [\\\|`\|\$(\|\${\|@]), [-1],
+[m4_if(m4_bregexp([$1], [#\|\\\|`\|\(\$\|@S|@\)\((|{|@{:@\)]), [-1],
        [AS_ECHO(["AS_ESCAPE([$1], [""])"]) >>confdefs.h],
        [cat >>confdefs.h <<_ACEOF
 [$1]


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