[Bug c++/98163] New: ICE symtab_node::verify failed, auto& NTTP specialized with same entity but different type.

[Bug c++/98163] New: ICE symtab_node::verify failed, auto& NTTP specialized with same entity but different type.

[leni536 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98163

            Bug ID: 98163
           Summary: ICE symtab_node::verify failed, auto& NTTP specialized
                    with same entity but different type.
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: leni536 at gmail dot com
  Target Milestone: ---

g++ (Compiler-Explorer-Build) 11.0.0 20201205 (experimental)

command line flags: -std=c++17 -pedantic-errors

```
template <auto& ref>
struct S {};

template <typename T>
void foo(T) {}

extern const int arr[];

// arr is const int[]
void bar(S<arr> s) {
    foo(s);
}

const int arr[2] = {1,2};

// arr is const int[2]
void baz(S<arr> s) {
    foo(s);
}
```

source>:19:1: error: Two symbols with same comdat_group are not linked by the
same_comdat_group list.
   19 | }
      | ^
_Z3fooI1SIL_Z3arrEEEvT_/4 (void foo(T) [with T = S<arr>]) @0x7f7216d81330
  Type: function definition analyzed
  Visibility: no_reorder public weak comdat
comdat_group:_Z3fooI1SIL_Z3arrEEEvT_ one_only
  previous sharing asm name: 3
  References: 
  Referring: 
  Function flags: body
  Called by: _Z3baz1SIL_Z3arrEE/2 
  Calls: 
_Z3fooI1SIL_Z3arrEEEvT_/3 (void foo(T) [with T = S<arr>]) @0x7f7216d81220
  Type: function definition analyzed
  Visibility: no_reorder public weak comdat
comdat_group:_Z3fooI1SIL_Z3arrEEEvT_ one_only
  next sharing asm name: 4
  References: 
  Referring: 
  Function flags: body
  Called by: _Z3bar1SIL_Z3arrEE/0 
  Calls: 
<source>:19:1: internal compiler error: symtab_node::verify failed
0x1c39f09 internal_error(char const*, ...)
        ???:0
0xacca22 symtab_node::verify_symtab_nodes()
        ???:0
0xae8def symbol_table::finalize_compilation_unit()
        ???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1

godbolt: https://godbolt.org/z/bKc1c1

[Bug c++/98163] ICE symtab_node::verify failed, auto& NTTP specialized with same entity but different type.

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98163

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Probably a dup of bug 91241.

[Bug c++/98163] ICE symtab_node::verify failed, auto& NTTP specialized with same entity but different type.

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98163

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2020-12-07
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
This one started with r7-4431-g4a826ca6feb3c7ec, it was rejected before that:

pr98163.C:1:17: error: ‘auto’ parameter not permitted in this context
 template <auto& ref>
                 ^~~
pr98163.C:10:15: note: invalid template non-type parameter
 void bar(S<arr> s) {
               ^
pr98163.C:17:15: note: invalid template non-type parameter
 void baz(S<arr> s) {
               ^

[Bug c++/98163] ICE symtab_node::verify failed, auto& NTTP specialized with same entity but different type.

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98163

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
and without the checking one gets an assembler error:

$ g++ pr98163.C -c -std=c++17 -pedantic-errors
/tmp/cclBTXg2.s: Assembler messages:
/tmp/cclBTXg2.s:70: Error: symbol `_Z3fooI1SIL_Z3arrEEEvT_' is already defined

so the checking really makes sense.

[Bug c++/98163] ICE symtab_node::verify failed, auto& NTTP specialized with same entity but different type.

[leni536 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98163

--- Comment #4 from Lénárd Szolnoki <leni536 at gmail dot com> ---
Other example in the same spirit, but not using array of unknown bound:

```
template <auto&>
struct S {};

template <typename T>
void foo(T) {}

int i;
constexpr const int& iref = i;

template void foo(S<i>);
template void foo(S<iref>);
```