[gdb/symtab] Add optimized out static var to cooked index

Consider the test-case:
...
$ cat main.c
int main (void) { return 0; }
$ cat static-optimized-out.c
static int aaa;
...
compiled like this:
...
$ gcc-12 static-optimized-out.c main.c -g -O2 -flto
...

There's a difference in behaviour depending on symtab expansion state:
...
$ gdb -q -batch a.out -ex "print aaa"
No symbol "aaa" in current context.
$ gdb -q -batch a.out -ex "maint expand-symtab" -ex "print aaa"
$1 = <optimized out>
...

The reason for the difference is that the optimized out variable aaa:
...
 <1><104>: Abbrev Number: 2 (DW_TAG_variable)
    <105>   DW_AT_name        : aaa
    <109>   DW_AT_decl_file   : 1
    <10a>   DW_AT_decl_line   : 18
    <10b>   DW_AT_decl_column : 12
    <10c>   DW_AT_type        : <0x110>
...
is not added to the cooked index because of this clause in abbrev_table::read:
...
     else if (!has_location && !has_specification_or_origin && !has_external
	       && cur_abbrev->tag == DW_TAG_variable)
	cur_abbrev->interesting = false;
...

Fix this inconsistency by making sure that the optimized out variable is added
to the cooked index.

Regression tested on x86_64-linux.

Add two test-cases, a C test-case gdb.opt/static-optimized-out.exp and a dwarf
assembly test-case gdb.dwarf2/static-optimized-out.exp.

Tested gdb.opt/static-optimized-out.exp with gcc-8 to gcc-12, for which we now
consistently get:
...
(gdb) print aaa^M
$1 = <optimized out>^M
...
and with gcc 7.5.0 and clang 13.0.1, for which we still consistently get:
...
(gdb) print aaa^M
No symbol "aaa" in current context.^M
...
due to missing debug info for the variable.

PR symtab/30656
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30656

Approved-By: Tom Tromey <tom@tromey.com>

1 files changed, 0 insertions, 9 deletions

diff --git a/gdb/dwarf2/abbrev.c b/gdb/dwarf2/abbrev.c
index 1ebf8f6..3a429fd 100644
--- a/gdb/dwarf2/abbrev.c
+++ b/gdb/dwarf2/abbrev.c
@@ -162,7 +162,6 @@ abbrev_table::read (struct dwarf2_section_info *section,
       bool has_specification_or_origin = false;
       bool has_name = false;
       bool has_linkage_name = false;
-      bool has_location = false;
       bool has_external = false;
 
       /* Now read in declarations.  */
@@ -217,11 +216,6 @@ abbrev_table::read (struct dwarf2_section_info *section,
 	      has_linkage_name = true;
 	      break;
 
-	    case DW_AT_const_value:
-	    case DW_AT_location:
-	      has_location = true;
-	      break;
-
 	    case DW_AT_sibling:
 	      if (is_csize && cur_attr.form == DW_FORM_ref4)
 		sibling_offset = size;
@@ -296,9 +290,6 @@ abbrev_table::read (struct dwarf2_section_info *section,
 	cur_abbrev->interesting = false;
       else if (!tag_interesting_for_index (cur_abbrev->tag))
 	cur_abbrev->interesting = false;
-      else if (!has_location && !has_specification_or_origin && !has_external
-	       && cur_abbrev->tag == DW_TAG_variable)
-	cur_abbrev->interesting = false;
       else
 	cur_abbrev->interesting = true;