Missing DWARF children for variable templates

Missing DWARF children for variable templates

[Nima Hamidi]

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Hello all,

When I compile

```
template <typename T>
struct Cls {
 static const int v = 0;
};

template <typename T>
int constexpr Cls_v = Cls<T>::v;

int func() {
 return Cls_v<int> + Cls_v<float>;
}
```

using `g++ -c main.cpp -o main.o -g`, I see two indistinguishable DIEs in the generated debug info:

```
< 1><0x0000003a> DW_TAG_variable
 DW_AT_name Cls_v
 DW_AT_decl_file 0x00000001
 DW_AT_decl_line 0x00000007
 DW_AT_decl_column 0x0000000f
 DW_AT_type <0x00000035>
 DW_AT_const_expr yes(1)
 DW_AT_location len 0x0009: 0x030000000000000000:
 DW_OP_addr 0x00000000

< 1><0x0000004d> DW_TAG_variable
 DW_AT_name Cls_v
 DW_AT_decl_file 0x00000001
 DW_AT_decl_line 0x00000007
 DW_AT_decl_column 0x0000000f
 DW_AT_type <0x00000035>
 DW_AT_const_expr yes(1)
 DW_AT_location len 0x0009: 0x030400000000000000:
 DW_OP_addr 0x00000004
```

Clang, however, generates DW_TAG_template_type_parameter children for these DIEs too:

```
< 1><0x0000003c> DW_TAG_variable
 DW_AT_name (indexed string: 0x00000003)Cls_v
 DW_AT_type <0x00000033>
 DW_AT_decl_file 0x00000001 /main.cpp
 DW_AT_decl_line 0x00000007
 DW_AT_const_value 0
< 2><0x00000045> DW_TAG_template_type_parameter
 DW_AT_type <0x0000004c>
 DW_AT_name (indexed string: 0x00000005)T
```

I was wondering if this is intentional or it’s just forgotten to be generated.

Thanks,
Nima

Re: Missing DWARF children for variable templates

[Nima Hamidi]

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Another similar issue is with alias templates. The following code:

```
template <typename T>
struct Cls {
 using ptr = T *;
};

template <typename T>
using Cls_ptr = typename Cls<T>::ptr;

Cls_ptr<int> ai;
Cls_ptr<float> af;
```

produces

```
< 1><0x00000029> DW_TAG_typedef
 DW_AT_type <0x0000003d>
 DW_AT_name (indexed string: 0x00000008)Cls_ptr<int>
 DW_AT_decl_file 0x00000001 /main.cpp
 DW_AT_decl_line 0x00000007
```

by  clang, but produces the following by gcc. (Note the difference in DW_AT_name’s.)

```
< 1><0x00000044> DW_TAG_typedef
 DW_AT_name Cls_ptr
 DW_AT_decl_file 0x00000001
 DW_AT_decl_line 0x00000007
 DW_AT_decl_column 0x00000007
 DW_AT_type <0x00000027>
```
On Nov 10, 2023 at 7:59 PM -0600, Nima Hamidi <nimaa.hamidi@gmail.com>, wrote:
>
> template <typename T>
> struct Cls {
>  static const int v = 0;
> };
>
> template <typename T>
> int constexpr Cls_v = Cls<T>::v;
>
> int func() {
>  return Cls_v<int> + Cls_v<float>;
> }

Re: Missing DWARF children for variable templates

[Jonathan Wakely]

On Sat, 11 Nov 2023 at 02:06, Nima Hamidi via Gcc <gcc@gcc.gnu.org> wrote:
>
> Another similar issue is with alias templates. The following code:

Please report both cases to Bugzilla, thanks.


>
> ```
> template <typename T>
> struct Cls {
>  using ptr = T *;
> };
>
> template <typename T>
> using Cls_ptr = typename Cls<T>::ptr;
>
> Cls_ptr<int> ai;
> Cls_ptr<float> af;
> ```
>
> produces
>
> ```
> < 1><0x00000029> DW_TAG_typedef
>  DW_AT_type <0x0000003d>
>  DW_AT_name (indexed string: 0x00000008)Cls_ptr<int>
>  DW_AT_decl_file 0x00000001 /main.cpp
>  DW_AT_decl_line 0x00000007
> ```
>
> by  clang, but produces the following by gcc. (Note the difference in DW_AT_name’s.)
>
> ```
> < 1><0x00000044> DW_TAG_typedef
>  DW_AT_name Cls_ptr
>  DW_AT_decl_file 0x00000001
>  DW_AT_decl_line 0x00000007
>  DW_AT_decl_column 0x00000007
>  DW_AT_type <0x00000027>
> ```
> On Nov 10, 2023 at 7:59 PM -0600, Nima Hamidi <nimaa.hamidi@gmail.com>, wrote:
> >
> > template <typename T>
> > struct Cls {
> >  static const int v = 0;
> > };
> >
> > template <typename T>
> > int constexpr Cls_v = Cls<T>::v;
> >
> > int func() {
> >  return Cls_v<int> + Cls_v<float>;
> > }