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[Bug c++/53540] New: C++11: using fails to be equivalent to typedef
- From: "akim.demaille at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Thu, 31 May 2012 14:38:48 +0000
- Subject: [Bug c++/53540] New: C++11: using fails to be equivalent to typedef
- Auto-submitted: auto-generated
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540
Bug #: 53540
Summary: C++11: using fails to be equivalent to typedef
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: akim.demaille@gmail.com
Created attachment 27532
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27532
test case
Hi all,
I hope this is not a bogus bug report, I apologize if there is something I
misunderstood. I observed the following with both 4.7.0 and "4.8":
g++-mp-4.7 (MacPorts gcc47 4.7.0_3) 4.7.0
Copyright (C) 2012 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.
g++-mp-4.8 (MacPorts gcc48 4.8-20120527_1) 4.8.0 20120527 (experimental)
Copyright (C) 2012 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.
In the following example, I import a type name from a templates struct with
"using", and do the same with "typedef". The latter works, but "using" does
not seem to find the definition. clang finds it though (but then again, my
understanding might be wrong).
If "function" is not templated, there is no problem.
$ cat foo.cc
template <typename T>
struct context
{
typedef int type;
};
template <typename T>
void function()
{
using ctx1 = context<T>;
typename ctx1::type f1;
typedef context<T> ctx2;
typename ctx2::type f2;
}
int main()
{
function<int>();
}
$ g++-mp-4.8 -Wall -std=c++11 foo.cc
foo.cc: In instantiation of 'void function() [with T = int]':
foo.cc:19:17: required from here
foo.cc:11:23: error: no type named 'type' in 'using ctx1 = struct context<T>'
typename ctx1::type f1;
^
foo.cc:14:23: warning: unused variable 'f2' [-Wunused-variable]
typename ctx2::type f2;
^