gdb/dwarf: skip type units in create_dwo_cus_hash_table

When compiling with -gsplit-dwarf -fdebug-types-section, DWARF 5
.debug_info.dwo sections may contain some type units:

    $ llvm-dwarfdump -F -color a-test.dwo | head -n 5
    a-test.dwo:     file format elf64-x86-64

    .debug_info.dwo contents:
    0x00000000: Type Unit: length = 0x000008a0, format = DWARF32, version = 0x0005, unit_type = DW_UT_split_type, abbr_offset = 0x0000, addr_size = 0x08, name = 'vector<int, std::allocator<int> >', type_signature = 0xb499dcf29e2928c4, type_offset = 0x0023 (next unit at 0x000008a4)

In this case, create_dwo_cus_hash_table wrongly creates a dwo_unit for
it and adds it to dwo_file::cus.  create_dwo_debug_type_hash_table later
correctly creates a dwo_unit that it puts in dwo_file::tus.

This can be observed with:

    $ ./gdb  -nx -q --data-directory=data-directory -ex 'maint set dwarf sync on' -ex "maint set worker-threads 0" -ex "set debug dwarf-read 2" -ex "file a.out" -batch
    ...
    [dwarf-read] create_dwo_cus_hash_table: Reading .debug_info.dwo for /home/smarchi/build/binutils-gdb/gdb/a-test.dwo:
    [dwarf-read] create_dwo_cus_hash_table:   offset 0x0, dwo_id 0xb499dcf29e2928c4
    [dwarf-read] create_dwo_cus_hash_table:   offset 0x8a4, dwo_id 0x496a8791a842701b
    [dwarf-read] create_dwo_cus_hash_table:   offset 0x941, dwo_id 0xefd13b3f62ea9fea
    ...
    [dwarf-read] create_dwo_debug_type_hash_table: Reading .debug_info.dwo for /home/smarchi/build/binutils-gdb/gdb/a-test.dwo
    [dwarf-read] create_dwo_debug_type_hash_table:   offset 0x0, signature 0xb499dcf29e2928c4
    [dwarf-read] create_dwo_debug_type_hash_table:   offset 0x8a4, signature 0x496a8791a842701b
    [dwarf-read] create_dwo_debug_type_hash_table:   offset 0x941, signature 0xefd13b3f62ea9fea
    ...

Fix it by skipping anything that isn't a compile unit in
create_dwo_cus_hash_table.  After this patch, the debug output of
create_dwo_cus_hash_table only shows one created dwo_unit, as we expect.

I couldn't find any user-visible problem related to this, I just noticed
it while debugging.

Change-Id: I7dddf766fe1164123b6702027b1beb56114f25b1
Reviewed-By: Tom de Vries <tdevries@suse.de>

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 7d6dfd03e272cc9d08ae3d7c6eda0ba35ca84ec2..794c3973cb56f61bbe96ff1462aa902e5a35da5f 100644 (file)
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -6342,6 +6342,12 @@ create_dwo_cus_hash_table (dwarf2_cu *cu, dwo_file &dwo_file)
       if (reader.is_dummy())
        continue;
 
+      /* DWARF 5 .debug_info.dwo sections may contain some type units.  Skip
+        everything that is not a compile unit.  */
+      if (const auto ut = reader.cu ()->header.unit_type;
+         ut != DW_UT_compile && ut != DW_UT_split_compile)
+       continue;
+
       std::optional<ULONGEST> signature
        = lookup_dwo_id (reader.cu (), reader.top_level_die ());
       if (!signature.has_value ())