gcc 4.9.0 -std=c++1y breakage

[Peter A. Bigot <pab@…>]

The program below fails to compile with development gcc in C++1y mode; it works in C++11 mode. I don't know whether this is a fault in gcc or in boost, but thought an early warning was worth providing. This is with the current super-project master branch; I believe it also fails on develop.

llc[900]$ cat /tmp/bre.cc 
#include <boost/regex.hpp>

const boost::regex e("AB");

llc[901]$ g++ --version
g++ (GCC) 4.9.0 20140104 (experimental)
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

llc[902]$ g++ -std=c++11 -I/opt/boost -c /tmp/bre.cc 
llc[903]$ g++ -std=c++1y -I/opt/boost -c /tmp/bre.cc 
In file included from /opt/boost/boost/regex/v4/regex.hpp:70:0,
                 from /opt/boost/boost/regex.hpp:31,
                 from /tmp/bre.cc:1:
/opt/boost/boost/regex/v4/basic_regex_creator.hpp: In member function ‘boost::re_detail::re_literal* boost::re_detail::basic_regex_creator<charT, traits>::append_literal(charT)’:
/opt/boost/boost/regex/v4/basic_regex_creator.hpp:347:24: error: lvalue required as increment operand
       ++(result->length);
                        ^
In file included from /opt/boost/boost/regex/v4/regex.hpp:73:0,
                 from /opt/boost/boost/regex.hpp:31,
                 from /tmp/bre.cc:1:
/opt/boost/boost/regex/v4/basic_regex_parser.hpp: In member function ‘bool boost::re_detail::basic_regex_parser<charT, traits>::parse_repeat(std::size_t, std::size_t)’:
/opt/boost/boost/regex/v4/basic_regex_parser.hpp:974:21: error: lvalue required as decrement operand
       --(lit->length);

[Marshall Clow]

Could you try this program with the gcc that you are using, please?

struct Foo { int length; };

int main () {
	Foo * p = new Foo { 0 };
	++(p->length);
	return 0;
	}

Thanks!

[Peter A. Bigot <pab@…>]

No issues.

llc[1036]$ g++ --version
g++ (GCC) 4.9.0 20140104 (experimental)
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

llc[1037]$ g++ -std=c++11 -c /tmp/f.cc 
llc[1038]$ g++ -std=c++1y -c /tmp/f.cc 
llc[1039]$

[Peter A. Bigot <pab@…>]

See the boost-dev mailing list for information relevant to this bug.

[Marshall Clow]

[ Marshall posting for Peter ]

This issue arose as of ​GCC SVN commit 197248 which implements ​N3582. It occurs because the ​change on line 4109 preserves parentheses at the front end (with that change reverted, gcc works correctly).

This is now ​PR C++/59681. The fix in GCC is not trivial, so I've just made ​pull #1 so the trivial fix for boost (remove the parens) can be applied.

[John Maddock]

This all appears to be working correctly in master and develop with gcc-4.9.0 and -std=gnu++1y so closing down.