[gdb] Expand symbolless symtabs using maint expand-symtabs

[gdb] Expand symbolless symtabs using maint expand-symtabs

Consider this test-case, consisting of header file hello.h:
...
inline static const char*
foo (void)
{
  return "foo";
}
...
and source file hello.c:
...
int
main (void)
{
  printf ("hello: %s\n", foo ());
  return 0;
}
...
compiled with -g:
...
$ gcc hello.c -g
...

When trying to expand the partial symtab for hello.h:
...
$ gdb -batch \
  -iex "set language c" \
  a.out \
  -ex "maint expand-symtabs hello.h" \
  -ex "maint info psymtabs"
...
we in fact find that the partial symtab for hello.h (and corresponding
includer partial symtab hello.c) have not been expanded:
...
  { psymtab hello.h ((struct partial_symtab *) 0x27cf070)
    readin no
  ...
  { psymtab hello.c ((struct partial_symtab *) 0x2cf09e0)
    readin no
...

This is due to the recursively_search_psymtabs call in
psym_expand_symtabs_matching:
...
      if (recursively_search_psymtabs (ps, objfile, domain,
                                      lookup_name, symbol_matcher))
...
which always returns false for symbolless partial symtabs.

The same problem occurs with CUs where the dwarf is generated by gas
--gdwarf-2 for a foo.S: if we read such a test-case with -readnow, we'll have
a symbolless symtab for foo.S.  But if we read the test-case with partial
symtabs, and expand those using "maint expand-symtabs", the foo.S psymtab
remains unexpanded.

Fix this by passing a NULL symbol_matcher and lookup_name to
expand_symtabs_matching in maintenance_expand_symtabs, and skipping the call
to recursively_search_psymtabs if symbol_matcher == NULL and
lookup_name == NULL.

Build and tested on x86_64-linux, with native.

In addition, tested test-case with target boards cc-with-gdb-index.exp,
cc-with-debug-names.exp and readnow.exp.

gdb/ChangeLog:

2020-04-14  Tom de Vries  <tdevries@suse.de>

	PR symtab/25720
	* symmisc.c (maintenance_expand_symtabs): Call expand_symtabs_matching
	with NULL symbol_matcher and lookup_name.
	* psymtab.c (psym_expand_symtabs_matching): Handle NULL symbol_matcher
	and lookup_name.
	* dwarf2/read.c (dw2_expand_symtabs_matching)
	(dw2_debug_names_expand_symtabs_matching): Same.
	* symfile.h (struct quick_symbol_functions::expand_symtabs_matching):
	Make lookup_name a pointer.  Update comment.
	* symtab.c (global_symbol_searcher::expand_symtabs): Handle
	lookup_name being a pointer.
	* symfile.c (expand_symtabs_matching): Same.
	* symfile-debug.c (debug_qf_expand_symtabs_matching): Same.
	* linespec.c (iterate_over_all_matching_symtabs): Same.

gdb/testsuite/ChangeLog:

2020-04-14  Tom de Vries  <tdevries@suse.de>

	PR symtab/25720
	* gdb.base/maint-expand-symbols-header-file.c: New test.
	* gdb.base/maint-expand-symbols-header-file.exp: New file.
	* gdb.base/maint-expand-symbols-header-file.h: New test.