PR c++/17976, symtab/17821

PR c++/17976, symtab/17821

This patch addresses two issues.

The basic problem is that "(anonymous namespace)" doesn't get entered
into the symbol table because when dwarf2read.c:new_symbol_full is called
the DIE has no name (dwarf2_name returns NULL).

PR 17976: ptype '(anonymous namespace)' should work like any namespace

PR 17821: perf issue looking up (anonymous namespace)

bash$ gdb monster-program
(gdb) mt set per on
(gdb) mt set symbol-cache-size 0
(gdb) break (anonymous namespace)::foo

Before:

Command execution time: 3.266289 (cpu), 6.169030 (wall)
Space used: 811429888 (+12910592 for this command)

After:

Command execution time: 1.264076 (cpu), 4.057408 (wall)
Space used: 798781440 (+0 for this command)

gdb/ChangeLog:

	PR c++/17976, symtab/17821
	* cp-namespace.c (cp_search_static_and_baseclasses): New parameter
	is_in_anonymous.  All callers updated.
	(find_symbol_in_baseclass): Ditto.
	(cp_lookup_nested_symbol_1): Ditto.  Don't search all static blocks
	for symbols in an anonymous namespace.
	* dwarf2read.c (namespace_name): Don't call dwarf2_name, fetch
	DW_AT_name directly.
	(dwarf2_name): Convert missing namespace name to
	CP_ANONYMOUS_NAMESPACE_STR.

gdeb/testsuite/ChangeLog:

	* gdb.cp/anon-ns.exp: Add test for ptype '(anonymous namespace)'.