[Bug c++/51385] Unnecessary instantiation converting to pointer to template class instance

[paolo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51385

--- Comment #5 from paolo at gcc dot gnu.org  ---
Author: paolo
Date: Mon Sep 29 09:06:31 2014
New Revision: 215680

URL: https://gcc.gnu.org/viewcvs?rev=215680&root=gcc&view=rev
Log:
2014-09-29  Paolo Carlini  

PR c++/51385
* g++.dg/template/pr51385.C: New.

Added:
trunk/gcc/testsuite/g++.dg/template/pr51385.C
Modified:
trunk/gcc/testsuite/ChangeLog

[Bug c++/51385] Unnecessary instantiation converting to pointer to template class instance

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51385

Paolo Carlini  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |FIXED
   Target Milestone|--- |4.9.0

--- Comment #6 from Paolo Carlini  ---
Done.

[Bug c++/51385] Unnecessary instantiation converting to pointer to template class instance

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51385

--- Comment #4 from Paolo Carlini  ---
This is fixed in 4.9.0, I'm adding the testcase and closing the bug.

[Bug c++/51385] Unnecessary instantiation converting to pointer to template class instance

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51385

--- Comment #3 from Jonathan Wakely  2011-12-02 
10:47:45 UTC ---
Interestingly G++ is happy to not instantiate the template when it's not
possible to, i.e. making this change and defining -DINCOMPLETE allows it to
compile:

template 
struct FussyTemplate
#ifndef INCOMPLETE
{
static_assert( test::value, "not short" );
}
#endif
;

But if the class template definition is available it gets instantiated.

[Bug c++/51385] Unnecessary instantiation converting to pointer to template class instance

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51385

Paolo Carlini  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2011-12-02
 CC||jason at gcc dot gnu.org
 Ever Confirmed|0   |1

--- Comment #2 from Paolo Carlini  2011-12-02 
10:42:28 UTC ---
Let's add Jason in CC, definitely not a regression, but the issue seems pretty
interesting, eh.

[Bug c++/51385] Unnecessary instantiation converting to pointer to template class instance

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51385

--- Comment #1 from Jonathan Wakely  2011-12-02 
10:36:14 UTC ---
Here's a version which isn't a compile-time-hog but demonstrates the
unnecessary instantiation with a static_assert (so needs -std=c++11)


template  struct NTmpl;
template  >
struct PtrConvs {
   enum { bad = 1 };
};

template 
struct PtrConvs >;

template struct test { static const bool value = true; };
template<> struct test { static const bool value = false; };

template 
struct FussyTemplate
{
static_assert( test::value, "not short" );
};

struct B { };

typedef char chk[1];
typedef char chk[PtrConvs, B>::bad];


EFG and Clang compile this happily, without instantiating FussyTemplate