g++1.35 evaluates expression twice when destructor is virtual

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2 total messages Started by Tom Vijlbrief Wed, 28 Jun 1989 10:23

#82

Author: Tom Vijlbrief
Date: Wed, 28 Jun 1989 10:23

56 lines
1963 bytes

G++ evaluates the expression b.delfunc(this) twice.
Discovered when porting ET++


g++ version 1.35.0
 /usr/local/lib/gcc-cpp -+ -v -undef -D__GNU__ -D__GNUG__ -D__cplusplus -Dmc68000 -Dsun -Dunix -D__mc68000__ -D__sun__ -D__unix__ -D__HAVE_68881__ -Dmc68020 doubledel.cc /tmp/cca04906.cpp
GNU CPP version 1.35
 /usr/local/lib/gcc-cc1plus /tmp/cca04906.cpp -quiet -dumpbase doubledel.cc -noreg -version -o /tmp/cca04906.s
GNU C++ version 1.35.0 (68k, MIT syntax) compiled by GNU C version 1.35.
 /usr/local/lib/gcc-as -mc68020 /tmp/cca04906.s -o doubledel.o
 /usr/local/lib/gcc-ld++ -C /usr/local/lib/crt0+.o /lib/Mcrt1.o doubledel.o -lg++ /usr/local/lib/gcc-gnulib -lc

tom@twilight:~/src/CC> a.out

called
called

=================================================
#include <stdio.h>

class del {
public:
  del() {};
  virtual ~del() {};
  virtual void bug();
  virtual del *delfunc(del*);
};

del b;

del *del::delfunc(del*)
{
  del *p= new del;
  fprintf(stderr, "called\n");
  return p;
}

void del::bug()
{
  delete b.delfunc(this);  // b.delfunc(this) is called twice !!!
}


main()
{
  del *a= new del;
  a->bug();
}
===============================================================================
Tom Vijlbrief
TNO Institute for Perception
P.O. Box 23				Phone: +31 34 63 562 11
3769 ZG  Soesterberg			E-mail: tnosoes!tom@mcvax.cwi.nl
The Netherlands				    or:	uunet!mcvax!tnosoes!tom
===============================================================================

g++1.35 evaluates expression twice when destructor is virtual

#313

Author: Michael Tiemann
Date: Tue, 01 Aug 1989 02:44

20 lines
994 bytes

    G++ evaluates the expression b.delfunc(this) twice.
    Discovered when porting ET++ [...]

Here is the fix (to function build_delete, near the top of the function):

*** cplus-init.c~	Fri Jul 28 14:56:18 1989
--- cplus-init.c	Mon Jul 31 19:39:05 1989
***************
*** 2704,2707 ****
--- 2704,2709 ----
  	  return expr;
  	}
+       if (TREE_VOLATILE (addr))
+ 	addr = save_expr (addr);
        ref = build_indirect_ref (addr, 0);
        ptr = 1;
yahi% 

Michael

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