Re: c++/1209: Enums as template parameters produce "can't find class" errors

[Daniel Jacobowitz <drow at mvista dot com>]

The following reply was made to PR c++/1209; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@mvista.com>
To: ervan@tharas.com
Cc: gdb-gnats@sources.redhat.com, ramesh@tharas.com
Subject: Re: c++/1209: Enums as template parameters produce "can't find class" errors
Date: Mon, 12 May 2003 22:42:18 -0400

 On Tue, May 13, 2003 at 01:07:12AM -0000, ervan@tharas.com wrote:
 > 
 > >Number:         1209
 > >Category:       c++
 > >Synopsis:       Enums as template parameters produce "can't find class" errors
 > >Confidential:   no
 > >Severity:       non-critical
 > >Priority:       medium
 > >Responsible:    unassigned
 > >State:          open
 > >Class:          sw-bug
 > >Submitter-Id:   net
 > >Arrival-Date:   Tue May 13 01:08:01 UTC 2003
 > >Closed-Date:
 > >Last-Modified:
 > >Originator:     Ervan Darnell
 > >Release:        5.3
 > >Organization:
 > >Environment:
 > Red Hat Linux on i686 and using g++ 3.2.2 both to compile gdb 
 > and the test program.
 > >Description:
 > When an integer-style template parameter is specified with 
 > an enum, the demangler sees the integer value but the stabs
 > encodes the enum name.  For instance:
 > 
 > enum GNetConn {  GSimpleNetConn,  GLongNetConn };
 > 
 > template <GNetConn T>
 > class Sub2 : public Base { ....
 > 
 > Will cause the stabs to have Sub2<GsimpleNetConn> but the 
 > demangling will report Sub2<(GNetConn) 0>.  While logically
 > the same, gdb cannot find the correct class based on the 
 > (GNetConn) 0 cast:
 > 
 > warning: can't find class named `SubSub<(GNetConn)0>', as given by C++ RTTI
 > 
 > and it fails completely to print anything (the full 
 > attached example has another level of subclassing). 
 > Even when the proper cast is explicitly given, it still reports 
 > the error, but at least it works:
 >  p *(SubSub<GSimpleNetConn>*)z
 > warning: can't find class named `SubSub<(GNetConn)0>', as given by C++ RTTI
 > warning: can't find class named `SubSub<(GNetConn)0>', as given by C++ RTTI
 > $7 = warning: can't find class named `SubSub<(GNetConn)0>', as given by C++ RTTI
 > {<Sub2<GSimpleNetConn>> = {<Base> = {_vptr.Base = 0x8049af0, i = 6}, 
 >     k = 6}, t = 5}  
 > 
 > 
 > This bears some resemblance to PR.488.
 > >How-To-Repeat:
 > g++ -g gdbprob.cc
 > gdb ./a.out
 > then breakpoint in foo and print argument z.  The attachment
 > contains the full gdb interaction.
 
 Thanks for the testcase.  I don't have time to investigate right now,
 but to leave myself a note for later:
   The demangler normally produces the SubSub<(GNetConn)0> form when using
 DMGL_VERBOSE, and the SubSub<GSimpleNetConn> form otherwise.  I can't
 see where GDB is being inconsistent, but the trick to this one will be
 tracking down where the demangler is returning the overly-verbose form.
 
 > >Fix:
 > 
 > >Release-Note:
 > >Audit-Trail:
 > >Unformatted:
 > ----gnatsweb-attachment----
 > Content-Type: application/octet-stream; name="gdbprob.cc"
 > Content-Transfer-Encoding: base64
 > Content-Disposition: attachment; filename="gdbprob.cc"
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 > 
 
 -- 
 Daniel Jacobowitz
 MontaVista Software                         Debian GNU/Linux Developer