gdb.c++ failures

[Jason Merrill <jason@redhat.com>]

I've been looking at the various C++ debugging failures on
i686-pc-linux-gnu using dwarf2.  Here's my analysis:

  anon-union.exp: The C++ compiler is emitting an extra lexical block, so
   the breakpoint on the closing brace is treated as being outside the
   scope of the variable.  There are two issues here: The compiler output
   is wrong, and the testcase is relying on corner-case behavior that only
   works for the outermost block of a function.  Of course, I don't know
   how we could test for the compiler bug without doing this, so I suppose
   we might as well leave the testcase alone.

  classes.exp: dwarf2 doesn't provide mangled names for abstract
   constructors, and there is a difference of opinion between the
   demangler and c-typeprint.c as to whether the type should be written "A
   const &" or "const A &".  The demangler always puts the cv-qualifier
   after the type it affects, whereas gdb puts it in front whenever that
   would have the correct meaning.  Either one could be changed to match
   the other, or the testcase could be modified to accept either form.
   Thoughts?

   Also, gdb is including artificial arguments in the printed
   representation of the constructors for vB-vD.  The dwarf2 output
   indicates that they are artificial; gdb should not print them.  There
   doesn't seem to be a simple way to handle this in the current gdb data
   structures.

  cplusfuncs.exp: cp-demangle bug.  The code to handle demangling
   pointers-to-functions isn't complex enough.

  local.exp: The test tries to examine InnerLocal outside of its scope,
   which fails.  Doing a ptype while InnerLocal is in scope works fine.
   Meanwhile, ptype Local works outside of Local's scope; apparently being
   inside an additional block makes a difference.  This definitely seems
   like a gdb issue.

  method.exp: The 'print this' tests are failing because gdb is printing
   the types as, say, (A * const), and the test just wants (A *).  The
   former is correct, since 'this' is readonly.  Any objection to changing
   the test (and others affected) to allow the const?

  namespace.exp: gdb prints '\0', the testcase expects '\000'.  An obvious
   fix, which I will apply.

  templates.exp: the artificial args problem breaks destructor
   recognition.  Also, when asked to set a breakpoint on a constructor, gdb
   offers a menu of the different clones, which the testcase doesn't
   like; it seems correct to me.

   Also, the cv-qual placement issue breaks 'print Foo<volatile char *>::foo';
   it needs to be 'print "Foo<char volatile*>::foo"' to match the demangler
   output.  I take it the aCC demangler makes different choices?  I don't
   see any way to get around the dependence of template naming on the
   canonical format chosen by the demangler unless gdb learns to mangle
   names itself; perhaps the syntax of the test should vary with the compiler.

Jason