c++/24367: Infinite recursion of typedef substitution

This bug finds another usage where we end up segfaulting while
normalizing user input.  inspect_type and replace_type recurse,
attempting to substitute the "real" symbol name for the typedef name.
However, since the both these names are the same, they keep calling
each other until the stack overflows.

A simple reproducer for it is given by

  typedef struct foo foo;
  int qux (foo *f) { return 0; }

  (gdb) b qux(foo*)
  Segmentation fault

inspect_type already contains some special handling to prevent a
similar situation from occurring with namespaces.  I wonder, however,
whether we need be so pedantic about the exact nature of the substitution.

This patch implements this rather more aggressive assumption that these
substitutions should be avoided whenever the replacement symbol's name is
exactly the same as the one we're trying to substitute.  [In the above
example, we're trying to substitute the tyepdef named "foo" with the symbol
named "foo" (a struct).]

gdb/ChangeLog:

	PR c++/24367
	* cp-support.c (inspect_type): Don't attempt substitutions
	of symbol with the same name.

gdb/testsuite/ChangeLog:

	PR c++/24367
	* gdb.cp/meth-typedefs.cc (incomplete_struct)
	(another_incomplete_struct, test_incomplete): New definitions.
	(main): Use new definitions.
	* gdb.cp/meth-typedefs.exp: Add new tests for `test_incomplete'
	functions.

1 files changed, 13 insertions, 3 deletions

diff --git a/gdb/cp-support.c b/gdb/cp-support.c
index d02a01d..4afb79a 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -190,10 +190,20 @@ inspect_type (struct demangle_parse_info *info,
 	  /* Get the real type of the typedef.  */
 	  type = check_typedef (otype);
 
-	  /* If the symbol is a namespace and its type name is no different
+	  /* If the symbol name is the same as the original type name,
+	     don't substitute.  That would cause infinite recursion in
+	     symbol lookups, as the typedef symbol is often the first
+	     found symbol in the symbol table.
+
+	     However, this can happen in a number of situations, such as:
+
+	     If the symbol is a namespace and its type name is no different
 	     than the name we looked up, this symbol is not a namespace
-	     alias and does not need to be substituted.  */
-	  if (TYPE_CODE (otype) == TYPE_CODE_NAMESPACE
+	     alias and does not need to be substituted.
+
+	     If the symbol is typedef and its type name is the same
+	     as the symbol's name, e.g., "typedef struct foo foo;".  */
+	  if (TYPE_NAME (type) != nullptr
 	      && strcmp (TYPE_NAME (type), name) == 0)
 	    return 0;