[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[ppalka at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Patrick Palka  changed:

   What|Removed |Added

 Resolution|--- |FIXED
 Status|ASSIGNED|RESOLVED

--- Comment #18 from Patrick Palka  ---
Fixed for GCC 13.2

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #17 from CVS Commits  ---
The releases/gcc-13 branch has been updated by Patrick Palka
:

https://gcc.gnu.org/g:20b1e1d8a79356e03f50f53e2fa02b376d56d7d7

commit r13-7327-g20b1e1d8a79356e03f50f53e2fa02b376d56d7d7
Author: Patrick Palka 
Date:   Fri May 12 08:37:54 2023 -0400

c++: remove redundant testcase [PR83258]

I noticed only after the fact that the new testcase template/function2.C
(from r14-708-gc3afdb8ba8f183) is just a subset of ext/visibility/anon8.C,
so let's get rid of it.

PR c++/83258

gcc/testsuite/ChangeLog:

* g++.dg/ext/visibility/anon8.C: Mention PR83258.
* g++.dg/template/function2.C: Removed.

(cherry picked from commit 10098788ff61467f5a499f01c5443fb53ff564dd)

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #16 from CVS Commits  ---
The releases/gcc-13 branch has been updated by Patrick Palka
:

https://gcc.gnu.org/g:42f9b481be3527b336b800128247d053fd18d121

commit r13-7324-g42f9b481be3527b336b800128247d053fd18d121
Author: Patrick Palka 
Date:   Thu May 11 10:04:25 2023 -0400

c++: converted lambda as template argument [PR83258, ...]

r8-1253-g3d2e25a240c711 removed the template argument linkage requirement
in convert_nontype_argument for C++17 (which r9-3836-g4be5c72cf3ea3e later
factored out into invalid_tparm_referent_p), but we need to also remove
the one in convert_nontype_argument_function for benefit of the first and
third testcase which we currently reject even in C++17/20 mode.

And in invalid_tparm_referent_p we're inadvertendly returning false for
the address of a lambda's static op() since it's DECL_ARTIFICIAL, which
currently causes us to reject the second (C++20) testcase.  But this
DECL_ARTIFICIAL check seems to be relevant only for VAR_DECL, and in fact
this code path was originally reachable only for VAR_DECL until recently
(r13-6970-gb5e38b1c166357).  So this patch restricts the check to VAR_DECL.

Co-authored-by: Jonathan Wakely 

PR c++/83258
PR c++/80488
PR c++/97700

gcc/cp/ChangeLog:

* pt.cc (convert_nontype_argument_function): Remove linkage
requirement for C++17 and later.
(invalid_tparm_referent_p) : Restrict
DECL_ARTIFICIAL rejection test to VAR_DECL.

gcc/testsuite/ChangeLog:

* g++.dg/ext/visibility/anon8.C: Don't expect a "no linkage"
error for the template argument :fn in C++17 mode.
* g++.dg/cpp0x/lambda/lambda-conv15.C: New test.
* g++.dg/cpp2a/nontype-class56.C: New test.
* g++.dg/template/function2.C: New test.

(cherry picked from commit c3afdb8ba8f1839544c414f57e41a58c8fda5349)

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #15 from CVS Commits  ---
The master branch has been updated by Patrick Palka :

https://gcc.gnu.org/g:10098788ff61467f5a499f01c5443fb53ff564dd

commit r14-787-g10098788ff61467f5a499f01c5443fb53ff564dd
Author: Patrick Palka 
Date:   Fri May 12 08:37:54 2023 -0400

c++: remove redundant testcase [PR83258]

I noticed only after the fact that the new testcase template/function2.C
(from r14-708-gc3afdb8ba8f183) is just a subset of ext/visibility/anon8.C,
so let's get rid of it.

PR c++/83258

gcc/testsuite/ChangeLog:

* g++.dg/ext/visibility/anon8.C: Mention PR83258.
* g++.dg/template/function2.C: Removed.

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[ppalka at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Patrick Palka  changed:

   What|Removed |Added

   Target Milestone|--- |13.2
 CC||ppalka at gcc dot gnu.org
   Assignee|unassigned at gcc dot gnu.org  |ppalka at gcc dot 
gnu.org
 Status|NEW |ASSIGNED

--- Comment #14 from Patrick Palka  ---
Fixed on trunk so far.

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #13 from CVS Commits  ---
The master branch has been updated by Patrick Palka :

https://gcc.gnu.org/g:c3afdb8ba8f1839544c414f57e41a58c8fda5349

commit r14-708-gc3afdb8ba8f1839544c414f57e41a58c8fda5349
Author: Patrick Palka 
Date:   Thu May 11 10:04:25 2023 -0400

c++: converted lambda as template argument [PR83258, ...]

r8-1253-g3d2e25a240c711 removed the template argument linkage requirement
in convert_nontype_argument for C++17 (which r9-3836-g4be5c72cf3ea3e later
factored out into invalid_tparm_referent_p), but we need to also remove
the one in convert_nontype_argument_function for benefit of the first and
third testcase which we currently reject even in C++17/20 mode.

And in invalid_tparm_referent_p we're inadvertendly returning false for
the address of a lambda's static op() since it's DECL_ARTIFICIAL, which
currently causes us to reject the second (C++20) testcase.  But this
DECL_ARTIFICIAL check seems to be relevant only for VAR_DECL, and in fact
this code path was originally reachable only for VAR_DECL until recently
(r13-6970-gb5e38b1c166357).  So this patch restricts the check to VAR_DECL.

Co-authored-by: Jonathan Wakely 

PR c++/83258
PR c++/80488
PR c++/97700

gcc/cp/ChangeLog:

* pt.cc (convert_nontype_argument_function): Remove linkage
requirement for C++17 and later.
(invalid_tparm_referent_p) : Restrict
DECL_ARTIFICIAL rejection test to VAR_DECL.

gcc/testsuite/ChangeLog:

* g++.dg/ext/visibility/anon8.C: Don't expect a "no linkage"
error for the template argument :fn in C++17 mode.
* g++.dg/cpp0x/lambda/lambda-conv15.C: New test.
* g++.dg/cpp2a/nontype-class56.C: New test.
* g++.dg/template/function2.C: New test.

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[egallager at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Eric Gallager  changed:

   What|Removed |Added

   See Also||https://gcc.gnu.org/bugzill
   ||a/show_bug.cgi?id=97700

--- Comment #12 from Eric Gallager  ---
(In reply to Johel Ernesto Guerrero Peña from comment #9)
> I think Bug 97700 is also a duplicate of this.

Well, it seems related enough, at least...

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #11 from Andrew Pinski  ---
(In reply to Jonathan Wakely from comment #4)
> Testcase from Bug 85589:
> 
> template struct foo {};
> 
> int main() {
> static auto v = "str";
> (void) foo {};
> }

Note comment #4 is already fixed (I reopened PR 85589 to close it was fixed [or
as a dup if I can find one]).

The rest of the testcases still fail on the trunk.

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[johelegp at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #10 from Johel Ernesto Guerrero Peña  ---
Another workaround, extended from Bug 92320's example. See
https://godbolt.org/z/69onWf.
You can wrap the closure object in a template function which itself invokes the
closure object and converts to a function pointer that GCC accepts.
```C++
template
void templ() {}

void dummy(){}

template
void fn(){F();}

void foo() {
constexpr int a = 7 + 3;
templ();

templ();

typedef void(FPtr)();
constexpr FPtr * b = 
templ();

constexpr auto l = []{};
constexpr void (*d)()=fn;
templ();

constexpr FPtr * c = [](){};
templ();
}

```

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[johelegp at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Johel Ernesto Guerrero Peña  changed:

   What|Removed |Added

 CC||johelegp at gmail dot com

--- Comment #9 from Johel Ernesto Guerrero Peña  ---
I think Bug 97700 is also a duplicate of this.

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[ma.noack.pr at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Matthias Noack  changed:

   What|Removed |Added

 CC||ma.noack.pr at gmail dot com

--- Comment #8 from Matthias Noack  ---
Still failing in 10.2 (original reproducer).

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[herring at lanl dot gov]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

S. Davis Herring  changed:

   What|Removed |Added

 CC||jason at gcc dot gnu.org

--- Comment #7 from S. Davis Herring  ---
My example in Comment #5 works in 9.2 but not in (Compiler Explorer's) trunk.

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Eric Gallager  changed:

   What|Removed |Added

 CC||jleahy+gcc at gmail dot com

--- Comment #6 from Eric Gallager  ---
*** Bug 92320 has been marked as a duplicate of this bug. ***

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[herring at lanl dot gov]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

S. Davis Herring  changed:

   What|Removed |Added

 CC||herring at lanl dot gov

--- Comment #5 from S. Davis Herring  ---
As an anti-example, making the client a template works:

template struct A{};

template
void f()
{
constexpr auto fp = +[]{};
A{};
}

int main()
{
f();
}

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #4 from Jonathan Wakely  ---
Testcase from Bug 85589:

template struct foo {};

int main() {
static auto v = "str";
(void) foo {};
}

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Jonathan Wakely  changed:

   What|Removed |Added

 CC||gufideg at gmail dot com

--- Comment #3 from Jonathan Wakely  ---
*** Bug 85589 has been marked as a duplicate of this bug. ***

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

--- Comment #2 from Jonathan Wakely  ---
With this patch:

--- a/gcc/cp/pt.c   
+++ b/gcc/cp/pt.c   
@@ -6259,7 +6259,8 @@ convert_nontype_argument_function (tree type, tree expr,  
 }  

   linkage = decl_linkage (fn_no_ptr);  
-  if (cxx_dialect >= cxx11 ? linkage == lk_none : linkage != lk_external)  
+  if ((cxx_dialect < cxx11 && linkage != lk_external)
+  || (cxx_dialect < cxx17 && linkage == lk_none))
 {
   if (complain & tf_error)
{

We accept Barry's testcase in C++17 mode.

I think we also need this for some non-type arguments without linkage:


@@ -6979,7 +6980,8 @@ convert_nontype_argument (tree type, tree expr,
tsubst_flags_t complain)

  /* DR 1155 allows internal linkage in C++11 and up.  */
  linkage_kind linkage = decl_linkage (expr);
- if (linkage < (cxx_dialect >= cxx11 ? lk_internal : lk_external))
+ if ((cxx_dialect < cxx11 && linkage < lk_external)
+ || (cxx_dialect < cxx17 && linkage < lk_internal))
{
  if (complain & tf_error)
error ("%qE is not a valid template argument for type %qT "


but that second change causes a new ice-on-invalid for this in C++17 mode (but
seems to correctly compile it when VALID is defined):


template  struct TestClass
{
  TestClass() : _val(val) { }
  T _val;
};

extern constexpr float e = 2.72;// external linkage
static constexpr float pi = 3.14;   // internal linkage

int main()
{
#ifdef VALID
  static
#endif
  constexpr float one = 1; // no linkage

  TestClass test1;

  TestClass test2;

  TestClass test3;
}


linkage.cc: In constructor 'TestClass::TestClass() [with T = float;
const T& val = one]':
linkage.cc:3:3: error: Local declaration from a different function
   TestClass() : _val(val) { }
   ^
one
linkage.cc:3:25: note: in statement
   TestClass() : _val(val) { }
 ^
one.2_1 = one;
during GIMPLE pass: cfg
linkage.cc:3:3: internal compiler error: verify_gimple failed
   TestClass() : _val(val) { }
   ^
0xdfad0d verify_gimple_in_cfg(function*, bool)
/home/jwakely/src/gcc/gcc/gcc/tree-cfg.c:5579
0xcc6956 execute_function_todo
/home/jwakely/src/gcc/gcc/gcc/passes.c:1994
0xcc79d2 execute_todo
/home/jwakely/src/gcc/gcc/gcc/passes.c:2048
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See  for instructions.

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Jonathan Wakely  changed:

   What|Removed |Added

 CC||xaxxon at gmail dot com

--- Comment #1 from Jonathan Wakely  ---
*** Bug 84981 has been marked as a duplicate of this bug. ***

[Bug c++/83258] Rejecting function pointer non-type template parameter without linkage

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83258

Jonathan Wakely  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2017-12-04
 Ever confirmed|0   |1