[Bug debug/86523] [9 Regression] ICE in gen_member_die, at dwarf2out.c:24933 starting from r262560

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86523

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
So there was no early debug info generated for the decl

 <var_decl 0x7ffff7fefb40 e
    type <record_type 0x7ffff6a86690 B readonly SI
...
    context <record_type 0x7ffff6a865e8 k>

in fact there's no early debug for anything besides the globals
c,d,f and g and artifical infrastructure.

Which is likely because everything is optimized away.  But we _do_ end up
assembling the instantiated k<int>::e.  Somehow dwarf2out_early_global_decl
doesn't see it but only the guard variable for its initialization.

This is because when the C++ FE calls rest_of_decl_compilation we
have current_function_decl set to __static_initialization_and_destruction_0
which looks spurious.

The following fixes that and properly generates debug info early (also
for non-LTO though that's currently harmless becuase we do not perform
free-lang-data):

diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index f8fc20e4093..d67ced097da 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -4754,14 +4754,14 @@ c_parse_final_cleanups (void)
             inline, with resulting performance improvements.  */
          tree ssdf_body;

+         /* Make sure the back end knows about all the variables.  */
+         write_out_vars (vars);
+
          /* Set the line and file, so that it is obviously not from
             the source file.  */
          input_location = locus_at_end_of_parsing;
          ssdf_body = start_static_storage_duration_function (ssdf_count);

-         /* Make sure the back end knows about all the variables.  */
-         write_out_vars (vars);
-
          /* First generate code to do all the initializations.  */
          if (vars)
            do_static_initialization_or_destruction (vars, /*initp=*/true);