[Bug debug/111080] New: restrict qualifier leaks debug info

[Bug debug/111080] New: restrict qualifier leaks debug info

[sagebar at web dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

            Bug ID: 111080
           Summary: restrict qualifier leaks debug info
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sagebar at web dot de
  Target Milestone: ---

The the following code example, debug information is retained for `struct foo`
even though that structure doesn't end up used:

Compile as `gcc -g -S -o - in.c | grep field_number`

```
struct foo {
        int field_number_1;
        int field_number_2;
        int field_number_3;
        int field_number_4;
        int field_number_5;
};

typedef int fun_t(struct foo *restrict);

int main() {
        return 0;
}
```

Output:
gcc -g -S -o - test.c | grep field_number
        .ascii "field_number_1\0"
        .ascii "field_number_2\0"
        .ascii "field_number_3\0"
        .ascii "field_number_4\0"
        .ascii "field_number_5\0"



When removing the `restrict` qualifier in the parameter of `funptr_t`, debug
information is not included in the produced assembly (as one would expect).

Here is a list of different declarations and where `struct foo` is leaked in
gcc 12.1.0:

> typedef int fun_t(struct foo *restrict);    // Leak
> typedef int fun_t(struct foo *);            // No leak
> typedef int (*fun_t)(struct foo *restrict); // Leak
> typedef int (*fun_t)(struct foo *);         // No leak
> extern int fun_t(struct foo *restrict);     // No leak
> extern int fun_t(struct foo *);             // No leak
> extern int (*fun_t)(struct foo *restrict);  // Leak
> extern int (*fun_t)(struct foo *);          // No leak
> static int fun_t(struct foo *restrict);     // No leak
> static int fun_t(struct foo *);             // No leak
> static int (*fun_t)(struct foo *restrict);  // Leak
> static int (*fun_t)(struct foo *);          // Leak (even w/o restrict!)
> int fun_t(struct foo *restrict);            // No leak
> int fun_t(struct foo *);                    // No leak
> int (*fun_t)(struct foo *restrict);         // Leak
> int (*fun_t)(struct foo *);                 // Leak (even w/o restrict!)

There is no difference when using `__restrict` or `__restrict__` instead.

[Bug debug/111080] restrict qualifier causes extra debug info to happen

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
> static int (*fun_t)(struct foo *);          // Leak (even w/o restrict!)
> int (*fun_t)(struct foo *);                 // Leak (even w/o restrict!)

The above should include the foo debug information as those are variable
definitions of a pointer to a function that has foo as an argument type.

[Bug debug/111080] [11/12/13/14 Regression] restrict qualifier causes extra debug info to happen

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|restrict qualifier causes   |[11/12/13/14 Regression]
                   |extra debug info to happen  |restrict qualifier causes
                   |                            |extra debug info to happen
      Known to work|                            |4.9.1
   Target Milestone|---                         |11.5
      Known to fail|                            |5.1.0

[Bug debug/111080] [11/12/13/14 Regression] restrict qualifier causes extra debug info to happen

[sagebar at web dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

--- Comment #2 from sagebar at web dot de ---
@Andrew Pinski

Of course: yes. I did make a mistake there, but only for this case:

> int (*fun_t)(struct foo *);                 // Leak (even w/o restrict!)

asm:
...
        .globl  fun_t
        .section        .bss
        .align 4
        .type   fun_t, @object
        .size   fun_t, 4
fun_t:
        .zero   4
...



In the other case:

> static int (*fun_t)(struct foo *);          // Leak (even w/o restrict!)

asm:
...
        # No data-symbol is generated for `fun_t`
...



Gcc actually doesn't generate a .bss-symbol for the static variable (since it's
unused), but it still generates debug inforation for `struct foo`. So I guess
strike `int (*fun_t)(struct foo *);` from the list, but keep `static int
(*fun_t)(struct foo *);` which still leaks

[Bug debug/111080] [11/12/13/14 Regression] restrict qualifier causes extra debug info to happen

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2023-08-21
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  This is because prune_unused_types_walk marks all restrict types as
necessary.  There's also DW_TAG_shared_type that's not handled.

[Bug debug/111080] [11/12/13/14 Regression] restrict qualifier causes extra debug info to happen

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|needs-bisection             |
           Priority|P3                          |P2

[Bug debug/111080] [11/12/13/14 Regression] restrict qualifier causes extra debug info to happen

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:bd2c4d6d8fffd5a6dae5217d6076cc4190bab13d

commit r14-3421-gbd2c4d6d8fffd5a6dae5217d6076cc4190bab13d
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Aug 21 10:34:30 2023 +0200

    debug/111080 - avoid outputting debug info for unused restrict qualified
type

    The following applies some maintainance with respect to type qualifiers
    and kinds added by later DWARF standards to prune_unused_types_walk.
    The particular case in the bug is not handling (thus marking required)
    all restrict qualified type DIEs.  I've found more DW_TAG_*_type that
    are unhandled, looked up the DWARF docs and added them as well based
    on common sense.

            PR debug/111080
            * dwarf2out.cc (prune_unused_types_walk): Handle
            DW_TAG_restrict_type, DW_TAG_shared_type, DW_TAG_atomic_type,
            DW_TAG_immutable_type, DW_TAG_coarray_type, DW_TAG_unspecified_type
            and DW_TAG_dynamic_type as to only output them when referenced.

            * gcc.dg/debug/dwarf2/pr111080.c: New testcase.

[Bug debug/111080] [11/12/13/14 Regression] restrict qualifier causes extra debug info to happen

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:fb6d61299159275246052c72c6e3666b36d5b333

commit r13-7750-gfb6d61299159275246052c72c6e3666b36d5b333
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Aug 21 10:34:30 2023 +0200

    debug/111080 - avoid outputting debug info for unused restrict qualified
type

    The following applies some maintainance with respect to type qualifiers
    and kinds added by later DWARF standards to prune_unused_types_walk.
    The particular case in the bug is not handling (thus marking required)
    all restrict qualified type DIEs.  I've found more DW_TAG_*_type that
    are unhandled, looked up the DWARF docs and added them as well based
    on common sense.

            PR debug/111080
            * dwarf2out.cc (prune_unused_types_walk): Handle
            DW_TAG_restrict_type, DW_TAG_shared_type, DW_TAG_atomic_type,
            DW_TAG_immutable_type, DW_TAG_coarray_type, DW_TAG_unspecified_type
            and DW_TAG_dynamic_type as to only output them when referenced.

            * gcc.dg/debug/dwarf2/pr111080.c: New testcase.

    (cherry picked from commit bd2c4d6d8fffd5a6dae5217d6076cc4190bab13d)

[Bug debug/111080] [11/12 Regression] restrict qualifier causes extra debug info to happen

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[11/12/13/14 Regression]    |[11/12 Regression] restrict
                   |restrict qualifier causes   |qualifier causes extra
                   |extra debug info to happen  |debug info to happen
      Known to fail|                            |13.2.0
      Known to work|                            |13.2.1, 14.0

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk and for GCC 13.3 sofar.

[Bug debug/111080] [11/12 Regression] restrict qualifier causes extra debug info to happen

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111080

--- Comment #7 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:5c3ab44771d0524140cf2ce5de594fcf7fefcd6f

commit r12-10044-g5c3ab44771d0524140cf2ce5de594fcf7fefcd6f
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Aug 21 10:34:30 2023 +0200

    debug/111080 - avoid outputting debug info for unused restrict qualified
type

    The following applies some maintainance with respect to type qualifiers
    and kinds added by later DWARF standards to prune_unused_types_walk.
    The particular case in the bug is not handling (thus marking required)
    all restrict qualified type DIEs.  I've found more DW_TAG_*_type that
    are unhandled, looked up the DWARF docs and added them as well based
    on common sense.

            PR debug/111080
            * dwarf2out.cc (prune_unused_types_walk): Handle
            DW_TAG_restrict_type, DW_TAG_shared_type, DW_TAG_atomic_type,
            DW_TAG_immutable_type, DW_TAG_coarray_type, DW_TAG_unspecified_type
            and DW_TAG_dynamic_type as to only output them when referenced.

            * gcc.dg/debug/dwarf2/pr111080.c: New testcase.

    (cherry picked from commit bd2c4d6d8fffd5a6dae5217d6076cc4190bab13d)