[Bug other/110885] New: "undefined reference" when using both "-fdebug-types-section" and "-gsplit-dwarf"

[Bug other/110885] New: "undefined reference" when using both "-fdebug-types-section" and "-gsplit-dwarf"

[linh.lrd at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885

            Bug ID: 110885
           Summary: "undefined reference" when using both
                    "-fdebug-types-section" and "-gsplit-dwarf"
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: linh.lrd at gmail dot com
  Target Milestone: ---

[Bug debug/110885] "undefined reference" when using both "-fdebug-types-section" and "-gsplit-dwarf"

[linh.lrd at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885

--- Comment #1 from Ling Nguyen <linh.lrd at gmail dot com> ---
Consider this program:
struct X
{
    static void foo() {}
};

struct Y
{
    template<auto func>
    static void bar() {}
};

int main()
{
    Y::bar<X::foo>();
    return 0;
}

If it's compiled using something like: gcc -gsplit-dwarf -fdebug-types-section.
the linker will complain: undefined reference to `X::foo()'
More details here: https://godbolt.org/z/qnj56e769

[Bug debug/110885] [10/11/12/13/14 Regression] "undefined reference" when using both "-fdebug-types-section" and "-gsplit-dwarf" and inline function as a template argument

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
            Summary|"undefined reference" when  |[10/11/12/13/14 Regression]
                   |using both                  |"undefined reference" when
                   |"-fdebug-types-section" and |using both
                   |"-gsplit-dwarf"             |"-fdebug-types-section" and
                   |                            |"-gsplit-dwarf" and inline
                   |                            |function as a template
                   |                            |argument
   Target Milestone|---                         |11.5
   Last reconfirmed|                            |2023-08-03

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Simplified testcase:
```
inline void foo() {}

struct Y
{
    template<void (*func)()>
    static void bar() {}
};

int main()
{
    Y::bar<foo>();
    return 0;
}
```

Confirmed.

[Bug debug/110885] [10/11/12/13/14 Regression] "undefined reference" when using both "-fdebug-types-section" and "-gsplit-dwarf" and inline function as a template argument

[linh.lrd at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885

--- Comment #3 from Ling Nguyen <linh.lrd at gmail dot com> ---
Thanks for quick responses.

A further look into the issue:
I believe there is bug in this piece of code:
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/dwarf2out.cc;h=fa0fe4c41bbd5b13aa5fe6cad6e7d39bbd82174a;hb=HEAD#l8501

It should probably be:
        if (is_template_instantiation (c))
          {
            /* Instantiated templates do not need to be cloned into the
               type unit.  Just move the DIE and its children back to
               the skeleton tree (in the main CU).  */
            remove_child_with_prev (c, prev);
            generate_skeleton_ancestor_tree (parent);
            add_child_die (parent->new_die, c);
            c = prev;
          }

Don't mean to teach a fish to swim here, because I'm no expert. Just want to
help to reduce the search space.
By the way, any chance for a fix (whenever it is) to land on gcc 10.2, as we
are fixed to it?

[Bug debug/110885] [10/11/12/13/14 Regression] "undefined reference" when using both "-fdebug-types-section" and "-gsplit-dwarf" and inline function as a template argument

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-debug
            Version|unknown                     |13.2.0

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
There's probably a duplicate about this.  I'll note that both -gsplit-dwarf and
more specifically -fdebug-types-section are unmaintained.  As a workaround
you can use -gdwarf-3 it seems.

[Bug debug/110885] [10/11/12/13/14 Regression] "undefined reference" when using both "-fdebug-types-section" and "-gsplit-dwarf" and inline function as a template argument

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |law at gcc dot gnu.org
           Priority|P3                          |P2