problem with uncomplete type

[Ulrich Lauther <ulrich dot lauther at mchp dot siemens dot de>]

The program below exposes two problems:
1. at the marked line, one would expect a compiler message, because an uncomplete
   type is used for template instantiation
2. If the method funny() is "commented in", the program gives a wrong result
   (I guess due to a wrong cast, which is caused by the incomplete type info).

I append the full source and a typescript of compilation.
The typescript is made with 2.95.1, but 2.95.2 has the same problem.

Kind regards

	-ulrich lauther

********************** source ***********************************

#include <stdio.h>
#include <stdlib.h>

struct dlink0 {
  dlink0* next;
  dlink0* last;
  inline dlink0() : next(0), last(0) {}
  inline dlink0* get_last() const  { return last;}
  inline dlink0* set_last(dlink0* p) { return last = p;}
};

template <class L>
class list_base {
  L* tail; 
public:
  inline list_base() : tail(0) {
  }
  inline void append(L* a) {
    if (tail) {
      a->next = tail->next;
      a->set_last(tail);
      a->next->set_last(tail->next = a);
    }
    else tail = a->next = a->set_last(a);
    tail = a;
  }
  inline L* first() const { return tail ? tail->next : (L*) 0; }
}; // list_base

template <class T, class L>
class ilist : private list_base<L> {
  int elements;
public:
  inline ilist() : elements(0) { // constructor
  }
  inline void append(const T* a) {
    list_base<L>::append((T*)a);
    elements++;
  }
  inline T* first() {return (T*) list_base<L>::first();}
}; // ilist

class MessLink;

struct space {
  int x[2];
};

class Fudge {
  public:
  ilist<MessLink,dlink0> mess_links; // would expect compiler complait here!!!

  /* without the (unused) method funny() everything runs o.k.
     with funny(), the program prints two different values, which is wrong
  */
  MessLink* funny() {
    return mess_links.first();
  }
};

class MessLink : public space, 
                 public dlink0 {
}; // MessLink

int main() {

  Fudge f;
  MessLink* tp = new MessLink;
  printf("append %p\n",tp);
  f.mess_links.append(tp);
  printf("first: %p\n",f.mess_links.first());
}

************************** compilation **********************************
Script started on Fri Sep 22 09:41:13 2000
bash$ g++ -v bug.C
Reading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/specs
gcc version 2.95.1 19990816 (release)
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/cpp -lang-c++ -v -D__GNUC__=2 -D__GNUG__=2 -D__GNUC_MINOR__=95 -D__cplusplus -D__ELF__ -Dunix -D__i386__ -Dlinux -D__ELF__ -D__unix__ -D__i386__ -D__linux__ -D__unix -D__linux -Asystem(posix) -D__EXCEPTIONS -Acpu(i386) -Amachine(i386) -Di386 -D__i386 -D__i386__ -Di686 -Dpentiumpro -D__i686 -D__i686__ -D__pentiumpro -D__pentiumpro__ bug.C /tmp/ccArL954.ii
GNU CPP version 2.95.1 19990816 (release) (i386 Linux/ELF)
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/../../../../include/g++-3
 /usr/local/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/../../../../i686-pc-linux-gnulibc1/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/include
 /usr/include
End of search list.
The following default directories have been omitted from the search path:
End of omitted list.
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/cc1plus /tmp/ccArL954.ii -quiet -dumpbase bug.cc -version -o /tmp/ccq4ssvc.s
GNU C++ version 2.95.1 19990816 (release) (i686-pc-linux-gnulibc1) compiled by GNU C version 2.95.1 19990816 (release).
 as -V -Qy -o /tmp/ccvjz7jS.o /tmp/ccq4ssvc.s
GNU assembler version 2.9.1 (i386-pc-linux-gnulibc1), using BFD version 2.9.1.0.19
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/collect2 -m elf_i386 -dynamic-linker /lib/ld-linux.so.1 /usr/lib/crt1.o /usr/lib/crti.o /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/crtbegin.o -L/usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1 -L/usr/local/i686-pc-linux-gnulibc1/lib -L/usr/local/lib /tmp/ccvjz7jS.o -lstdc++ -lm -lgcc -lc -lgcc /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/2.95.1/crtend.o /usr/lib/crtn.o
bash$ a.out
append 0x8049c00
first: 0x8049c08
bash$ exit
exit

Script done on Fri Sep 22 09:41:48 2000
-- 
	-lauther

----------------------------------------------------------------------------
Ulrich Lauther          ph: +49 89 636 48834 fx: ... 636 42284
Siemens ZT SE 4         Internet: Ulrich.Lauther@mchp.siemens.de