[binutils-gdb] Fix two buglets in .debug_names dumping

[binutils-gdb] Fix two buglets in .debug_names dumping

[Tom Tromey]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e0a874120a21bd460bd922c337f4869f72751dcf

commit e0a874120a21bd460bd922c337f4869f72751dcf
Author: Tom Tromey <tom@tromey.com>
Date:   Mon Dec 4 07:48:42 2023 -0700

    Fix two buglets in .debug_names dumping
    
    While working on gdb's .debug_names writer, I found a couple of small
    bugs in binutils .debug_names dumping.
    
    First, the DWARF spec (section 6.1.1.4.6 Name Table) says:
    
        These two arrays are indexed starting at 1, [...]
    
    I think it is clearer for binutils to follow this, particularly
    because DW_IDX_parent refers to this number.
    
    Second, I think the handling of an empty hash table is slightly wrong.
    Currently the dumping code assumes there is always an array of hashes.
    However, section 6.1.1.4.5 Hash Lookup Table says:
    
        The optional hash lookup table immediately follows the list of
        type signatures.
    
    and then:
    
        The hash lookup table is actually two separate arrays: an array of
        buckets, followed immediately by an array of hashes.
    
    My reading of this is that the hash table as a whole is optional, and
    so the hashes will not exist in this case.  (This also makes sense
    because the hashes are not useful without the buckets anyway.)
    
    This patch fixes both of these problems.  FWIW I have some gdb patches
    in progress that change gdb both to omit the hash table and to use
    DW_IDX_parent.
    
    2023-12-04  Tom Tromey  <tom@tromey.com>
    
            * dwarf.c (display_debug_names): Handle empty .debug_names hash
            table.  Name entries start at 1.

Diff:
---
 binutils/ChangeLog |  5 +++++
 binutils/dwarf.c   | 11 ++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index b53a9e9ccd1..cfe081a4118 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,8 @@
+2023-12-04  Tom Tromey  <tom@tromey.com>
+
+	* dwarf.c (display_debug_names): Handle empty .debug_names hash
+	table.  Name entries start at 1.
+
 2023-11-15  Arsen Arsenović  <arsen@aarsen.me>
 
 	* aclocal.m4: Regenerate.
diff --git a/binutils/dwarf.c b/binutils/dwarf.c
index 9e7d8753148..47eadfd1c67 100644
--- a/binutils/dwarf.c
+++ b/binutils/dwarf.c
@@ -10353,7 +10353,8 @@ display_debug_names (struct dwarf_section *section, void *file)
       const uint32_t *const hash_table_buckets = (uint32_t *) hdrptr;
       hdrptr += bucket_count * sizeof (uint32_t);
       const uint32_t *const hash_table_hashes = (uint32_t *) hdrptr;
-      hdrptr += name_count * sizeof (uint32_t);
+      if (bucket_count != 0)
+	hdrptr += name_count * sizeof (uint32_t);
       unsigned char *const name_table_string_offsets = hdrptr;
       hdrptr += name_count * offset_size;
       unsigned char *const name_table_entry_offsets = hdrptr;
@@ -10478,8 +10479,12 @@ display_debug_names (struct dwarf_section *section, void *file)
 	  p = name_table_entry_offsets + namei * offset_size;
 	  SAFE_BYTE_GET (entry_offset, p, offset_size, unit_end);
 
-	  printf ("[%3u] #%08x %s:", namei, hash_table_hashes[namei],
-		  fetch_indirect_string (string_offset));
+	  /* The name table is indexed starting at 1 according to
+	     DWARF, so be sure to use the DWARF numbering here.  */
+	  printf ("[%3u] ", namei + 1);
+	  if (bucket_count != 0)
+	    printf ("#%08x ", hash_table_hashes[namei]);
+	  printf ("%s:", fetch_indirect_string (string_offset));
 
 	  unsigned char *entryptr = entry_pool + entry_offset;