[Bug libstdc++/29286] [4.0/4.1/4.2/4.3 Regression] placement new does not change the dynamic type as it should

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #62 from rguenth at gcc dot gnu dot org  2007-05-14 16:20 -------
We ICE with

template <class T, class T2, int D>
class Vector
{
public:
   Vector()
   {
     for (int i = 0; i < D; ++i)
        new (&x_m[i]) T2();
   }
   T2& operator[](int i) { return *reinterpret_cast<T2*>(&x_m[i]); }

private:
   T x_m[D];
};

void foo(Vector<double, long, 3> *m)
{
  Vector<double, long, 3> v;
  v[0] = 1;
  v[1] = 2;
  v[2] = 3;
  *m = v;
}

(adjust the storage type to be of same size for double/long):

Program received signal SIGSEGV, Segmentation fault.
0x0000000000b11a5e in unmodifiable_var_p (var=0x0)
    at /space/rguenther/src/svn/trunk/gcc/tree-flow-inline.h:1598
1598      if (TREE_CODE (var) == SSA_NAME)

#0  0x0000000000b11a5e in unmodifiable_var_p (var=0x0)
    at /space/rguenther/src/svn/trunk/gcc/tree-flow-inline.h:1598
#1  0x0000000000b194c3 in may_alias_p (ptr=0x2b537d358210, mem_alias_set=2, 
    var=0x2b537d359e00, var_alias_set=3, alias_set_only=0 '\0')
    at /space/rguenther/src/svn/trunk/gcc/tree-ssa-alias.c:2685
#2  0x0000000000b17f2b in add_flow_insensitive_var_aliases (ai=0x14d7890, 
    pvar=0x2b537d358210, set=2, tag=0x2b537d356ba0)
    at /space/rguenther/src/svn/trunk/gcc/tree-ssa-alias.c:2190
#3  0x0000000000b184d3 in compute_change_dynamic_type_aliasing (
    vcdt=0x2b537d357a00, vai=0x14d7890)
    at /space/rguenther/src/svn/trunk/gcc/tree-ssa-alias.c:2242
#4  0x000000000098a387 in pointer_set_traverse (pset=0x14e4e10, 
    fn=0xb17f84 <compute_change_dynamic_type_aliasing>, data=0x14d7890)
    at /space/rguenther/src/svn/trunk/gcc/pointer-set.c:181
#5  0x0000000000b18719 in compute_flow_insensitive_aliasing (ai=0x14d7890)
    at /space/rguenther/src/svn/trunk/gcc/tree-ssa-alias.c:2295
#6  0x0000000000b15b17 in compute_may_aliases ()

where in may_alias_p the ptr we passed does not have a symbol memory tag
associated.  (but var is SFT.3)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29286