C++ related core dump

[Mark Kettenis <kettenis at jive dot nl>]

I'm debugging some evil C++ code at work, and gdb keeps dumping core
on me:

(gdb) ptype antennac 
type = class ROScalarColumn<int> : public virtual ROTableColumn {
  protected:
    Bool *canAccessColumn_p;
    Bool *reaskAccessColumn_p;

  public:
    ROScalarColumn();
    ROScalarColumn(Table const&, String const&);
    ROScalarColumn(ROTableColumn const&);
    ROScalarColumn(ROScalarColumn<int> const&);
    virtual ~ROScalarColumn();
    virtual class ROTableColumn * clone() const;
    void reference(ROScalarColumn<int> const&);
    void attach(Table const&, String const&);
    void get(unsigned int, int&) const;
    Int operator()(unsigned int) const;
    void getColumn(Vector<int>&, bool) const;
    Vector<int> getColumn() const;
    void getColumnRange(ArraySlicer const&, Vector<int>&, bool) const;
    Vector<int> getColumnRange(ArraySlicer const&) const;
    void getColumnCells(RefRows const&, Vector<int>&, bool) const;
    Vector<int> getColumnCells(RefRows const&) const;
  private:
    ROScalarColumn<int> & operator=(ROScalarColumn<int> const&);
    void reference(ROTableColumn const&);
    void checkDataType() const;
}

(gdb) p antennac(0)
Segmentation fault (core dumped)

This is with gcc 3.2 on sparc-sun-solaris2.7, which still uses stabs
debugging info.

I tracked it down to some code in valops.c:find_overload_match(),
where SYMBOL_CPLUS_DEMANGLED_NAME is returning a null pointer which we
pass to cp_func_name() and that function can't deal with that.  As a
stopgap, I applied the attached patch, and now I get:

(gdb) p antennac(0)
Invalid data type for function to be called.

which isn't quite what I want, but at least keeps my gdb alive.

What I really want of course is for the above to invoke
antennac.operator()(0).  Is that supposed to work at all?  I know
stabs support for C++ has issues, but reading the code I don't see how
this would work for DWARF2 either.

Regardless of properly invoking operator(), we should do something
about this crash.  Can we do something better than the attached patch?

Mark

Index: valops.c
===================================================================
RCS file: /cvs/src/src/gdb/valops.c,v
retrieving revision 1.161
diff -u -p -r1.161 valops.c
--- valops.c	27 May 2005 04:39:32 -0000	1.161
+++ valops.c	15 Nov 2005 09:52:56 -0000
@@ -1847,7 +1847,8 @@ find_overload_match (struct type **arg_t
   else
     {
       const char *qualified_name = SYMBOL_CPLUS_DEMANGLED_NAME (fsym);
-      func_name	= cp_func_name (qualified_name);
+      if (qualified_name)
+	func_name = cp_func_name (qualified_name);
 
       /* If the name is NULL this must be a C-style function.
          Just return the same symbol. */