[Bug c++/56377] New: [4.8 Regression] template args in substitution-failure diagnostics

[pl.smith.mail at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

 Bug #: 56377
   Summary: [4.8 Regression]  template args in
substitution-failure diagnostics
Classification: Unclassified
   Product: gcc
   Version: 4.8.0
Status: UNCONFIRMED
  Severity: minor
  Priority: P3
 Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: pl.smith.m...@gmail.com


When a candidate function for which substituion failed is listed in a
diagnostic, if the failure stems from a template parameter that have an
explicit argument, the explicit arguments are listed as .

For example:

template 
typename T::type f();

int main () {
  f();
}

Produces (4.8, no flags):

test.cpp: In function ג€˜int main()ג€™:
test.cpp:5:10: error: no matching function for call to 'f()'
   f();
  ^
test.cpp:5:10: note: candidate is:
test.cpp:2:18: note: template typename T::type f()
 typename T::type f();
  ^
test.cpp:2:18: note:   template argument deduction/substitution failed:
  *
test.cpp: In substitution of 'template typename T::type f() [with T =
]':
  *
test.cpp:5:10:   required from here
test.cpp:2:18: error: 'int' is not a class, struct, or union type

In 4.7 it is "[with T = int]".

[Bug c++/56377] [4.8 Regression] template args in substitution-failure diagnostics

[pl.smith.mail at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377



--- Comment #1 from Paul Smith  2013-02-18 
16:12:00 UTC ---

Looks like this was introduced in rev. 190664, with the merging of

'deduction_tsubst_fntype' into 'fn_type_unification'.



The instantiation context is constructed with 'targs' as the vector of template

arguments, which is still empty when substituting the explicit arguments into

the function type the first time. This can be fixed by either constructing the

instantiation context using 'explicit_targs' when non-null, or by copying

'explicit_targs' into 'targs' before the substitution.

[Bug c++/56380] New: Const/reference mutable members are not always rejected in class templates

[pl.smith.mail at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56380



 Bug #: 56380

   Summary: Const/reference mutable members are not always

rejected in class templates

Classification: Unclassified

   Product: gcc

   Version: unknown

Status: UNCONFIRMED

  Severity: normal

  Priority: P3

 Component: c++

AssignedTo: unassig...@gcc.gnu.org

ReportedBy: pl.smith.m...@gmail.com





GCC (all versions?) accepts mutable members of const-qualified/reference type

in class templates, if the const-ness/reference-ness is introduced during

instantiation:



template 

struct X {

  X();

  mutable T x;

};



X a; // no error

X b;  // no error

[Bug c++/56377] [4.8 Regression] template args in substitution-failure diagnostics

[pl.smith.mail at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Paul Smith  changed:

   What|Removed |Added

 Status|RESOLVED|REOPENED
 Resolution|FIXED   |

--- Comment #5 from Paul Smith  2013-02-23 
15:15:47 UTC ---
There can still be  arguments before the substitution:

template 
void f() {
  f();
}

int main() {
  f<0>();
}

Output:

test.cpp:3:11: error: template instantiation depth exceeds maximum of 900 (use
-ftemplate-depth= to increase the maximum) substituting ‘template void
f() [with int N = ]’
  f();
   ^
...