[Bug debug/98751] New: libgccjit fails in DWARF 5 handling with "`.Ldebug_loc2' is already defined" asm error

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98751

            Bug ID: 98751
           Summary: libgccjit fails in DWARF 5 handling with
                    "`.Ldebug_loc2' is already defined" asm error
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dmalcolm at gcc dot gnu.org
  Target Milestone: ---

Most of the jit.exp testsuite is failing, where the tests fail on 3rd
in-process iteration, with asm errors of the form:
   symbol `.Ldebug_loc2' is already defined
 test-factorial.c.exe iteration 3 of 5: writing reproducer to
./test-factorial.c.exe.reproducer.c
/tmp/libgccjit-7lPSFo/fake.s: Assembler messages:
/tmp/libgccjit-7lPSFo/fake.s:145: Error: symbol `.Ldebug_loc2' is already
defined
./test-factorial.c.exe: error: error invoking gcc driver
        FAILED: test-factorial.c.exe iteration 3 of 5: verify_code: result is
NULL

Adding this to set_options in jit.dg/harness.h:
  gcc_jit_context_set_bool_option (
    ctxt,
    GCC_JIT_BOOL_OPTION_KEEP_INTERMEDIATES,
    1);
allows the asm to be inspected after the test runs which has:

1st iteration:
 138   │     .section    .debug_loclists,"",@progbits
 139   │     .long   .Ldebug_loc3-.Ldebug_loc2
 140   │ .Ldebug_loc2:
 141   │     .value  0x5
 142   │     .byte   0x8
 143   │     .byte   0
 144   │     .long   0
 145   │ .Ldebug_loc0:
 146   │ .LLST0:

2nd iteration:

 138   │     .section    .debug_loclists,"",@progbits
 139   │     .long   .Ldebug_loc3-.Ldebug_loc2
 140   │ .Ldebug_loc2:
 141   │     .value  0x5
 142   │     .byte   0x8
 143   │     .byte   0
 144   │     .long   0
 145   │ .Ldebug_loc1:
 146   │ .LLST0:

3rd iteration:

 138   │     .section    .debug_loclists,"",@progbits
 139   │     .long   .Ldebug_loc3-.Ldebug_loc2
 140   │ .Ldebug_loc2:
 141   │     .value  0x5
 142   │     .byte   0x8
 143   │     .byte   0
 144   │     .long   0
 145   │ .Ldebug_loc2:
 146   │ .LLST0:

Note how line 145's number increments each time, and on the 3rd iteration is a
duplicate, leading to failure.

The bogus label is being emitted at:
  31673       ASM_OUTPUT_LABEL (asm_out_file, loc_section_label);

init_sections_and_labels:
  ASM_GENERATE_INTERNAL_LABEL (loc_section_label, DEBUG_LOC_SECTION_LABEL,
                               generation);

where "generations" is a static local to init_sections_and_labels that
increments, and thus eventually hits the duplicate value.

It looks like generations is meant to be just 0 or 1, but in libgccjit the
compilation code can get repeatedly invoked an arbitrary number of times in
process.  If generations is meant to be just 0 or 1, should this value be reset
to 0 at the end of toplev::main ?  Doing so is likely to fix this bug.