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Fixed a couple of bugs, updated many comments, and am including a comprehensive test for when there are only 3 types in place. I need to do something similar for 4 and maybe more types, but I'm not sure how comprehensive I can make the test at 4 and above types. 

llvm-svn: 148038
This commit is contained in:
Howard Hinnant 2012-01-12 19:48:14 +00:00
parent b02c5e9356
commit af07bfdb67
2 changed files with 2565 additions and 47 deletions
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159
libcxxabi/src/private_typeinfo.cpp
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@ -62,6 +62,11 @@ __class_type_info::~__class_type_info()
// __dynamic_cast notes:
// Up or above refers to base classes and base objects.
// Down or below refers to derived classes/objects.
// There are two search algorithms, search1 and search2.
// search1 is nothing but an optimization of search2 for a special case.
// Take it away and things should still work correctly.
// Both algorithms return 1 if the search should continue below the current node
// and 0 if the search should be aborted (because the answer is now known).
// search1 is a search algorithm used by __dynamic_cast.
// If a static_type is found
@ -73,9 +78,34 @@ __class_type_info::~__class_type_info()
// Else
// Continue search above and below this node.
// search2 is a search algorithm used by __dynamic_cast.
// if this is a dst_type
// if this node has already been classified then
// If the path to get here is public, overwrite existing path_dynamic_ptr_to_dst_ptr.
// else we haven't been to this (ptr, dst_type) before.
// Record the path to get here in path_dynamic_ptr_to_dst_ptr.
// For each base is (static_ptr, static_type) above this dst_type?
// Yes:
// Record it as dst_ptr_leading_to_static_ptr and increment the
// number of such recordings.
// If this is not the first of such recordings, then stop searching.
// Otherwise continue searching both above and below this node.
// No:
// record it as dst_ptr_not_leading_to_static_ptr and increment
// the number of such recordings.
// Continue searching both above and below this node.
// else if this is a static_type
// if this is *our* static_type
// if we found it above a dst_type, record the path from the dst_type
// else record the path from the dynamic_type being careful not to overwrite a
// previous public path in this latter case.
// Record that we found our static_type.
// Continue searching only below this node
// else
// Continue searching above and below this node.
// __class_type_info::search1
// There are no nodes to search above this node
// Returns: 1 if search should be continued, otherwise 0
int
__class_type_info::search1(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
@ -95,30 +125,8 @@ __class_type_info::search1(__dynamic_cast_info* info, const void* dynamic_ptr,
return 1;
}
// search2 is a search algorithm used by __dynamic_cast.
// if this is a dst_type
// if this has already been classified then
// If the path to get here is public, overwrite existing path_dynamic_ptr_to_dst_ptr.
// else we haven't been to this dst_type before.
// Record the path to get here in path_dynamic_ptr_to_dst_ptr.
// Is (static_ptr, static_type) above this dst_type?
// Yes:
// Record it as dst_ptr_leading_to_static_ptr and increment the
// number of such recordings.
// If this is not the first of such recordings, then stop searching.
// Otherwise continue searching both above and below this node.
// No:
// record it as dst_ptr_not_leading_to_static_ptr and increment
// the number of such recordings.
// else if this is a static_type
// if this is *our* static_type
// if we found it above a dst_type, record the path from the dst_type
// else record the path from the dynamic_type being careful not to overwrite a
// previous public path in this latter case.
// Record that we found our static_type.
// Continue searching only below this node
// else
// Continue searching above and below this node.
// __class_type_info::search2
// There are no nodes to search above this node
int
__class_type_info::search2(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
@ -160,6 +168,9 @@ __si_class_type_info::~__si_class_type_info()
{
}
// __si_class_type_info::search1
// There is one node to search above this node. The path to it is public
// and dynamic_ptr needs no adjustment in moving to that node.
int
__si_class_type_info::search1(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
@ -179,6 +190,9 @@ __si_class_type_info::search1(__dynamic_cast_info* info, const void* dynamic_ptr
return __base_type->search1(info, dynamic_ptr, path_below);
}
// __si_class_type_info::search2
// There is one node to search above this node. The path to it is public
// and dynamic_ptr needs no adjustment in moving to that node.
int
__si_class_type_info::search2(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
@ -237,6 +251,11 @@ __vmi_class_type_info::~__vmi_class_type_info()
{
}
// __vmi_class_type_info::search1
// There are one or more nodes to search above this node. The path to it
// may be public or not and the dynamic_ptr may need to be adjusted. Both
// of these details are handled by a pseudo-node in __base_class_type_info
// which has no type associated with it.
int
__vmi_class_type_info::search1(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
@ -263,21 +282,11 @@ __vmi_class_type_info::search1(__dynamic_cast_info* info, const void* dynamic_pt
return 1;
}
int
__base_class_type_info::search1(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
{
ptrdiff_t offset_to_base = __offset_flags >> __offset_shift;
if (__offset_flags & __virtual_mask)
{
char* vtable = *(char**)dynamic_ptr;
offset_to_base = (ptrdiff_t)vtable[offset_to_base];
}
return __base_type->search1(info, (char*)dynamic_ptr + offset_to_base,
(__offset_flags & __public_mask) ? path_below :
not_public_path);
}
// __vmi_class_type_info::search2
// There are one or more nodes to search above this node. The path to it
// may be public or not and the dynamic_ptr may need to be adjusted. Both
// of these details are handled by a pseudo-node in __base_class_type_info
// which has no type associated with it.
int
__vmi_class_type_info::search2(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
@ -297,10 +306,10 @@ __vmi_class_type_info::search2(__dynamic_cast_info* info, const void* dynamic_pt
for (Iter p = __base_info, e = __base_info + __base_count; p < e; ++p)
{
info->above_dst_ptr = true;
int r = p->search2(info, dynamic_ptr, public_path);
// Only a dst_type can abort the search, and one can't be
// above here. So it is safe to ignore return.
(void)p->search2(info, dynamic_ptr, public_path);
info->above_dst_ptr = false;
if (r == 0)
return 0;
if (info->found_static_ptr)
{
info->found_static_ptr = false;
@ -339,6 +348,35 @@ __vmi_class_type_info::search2(__dynamic_cast_info* info, const void* dynamic_pt
return 1;
}
// __base_class_type_info::search1
// This is a psuedo-node which does nothing but adjust the path access and
// dynamic_ptr prior to calling the base node above.
// The dynamic_ptr adjustment depends upon whether or not this node is marked
// virtual.
// If the path up is public, no change is made to the path (it may already be
// marked private from below). If the path up is private, it is forced so.
int
__base_class_type_info::search1(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
{
ptrdiff_t offset_to_base = __offset_flags >> __offset_shift;
if (__offset_flags & __virtual_mask)
{
char* vtable = *(char**)dynamic_ptr;
offset_to_base = *(ptrdiff_t*)(vtable + offset_to_base);
}
return __base_type->search1(info, (char*)dynamic_ptr + offset_to_base,
(__offset_flags & __public_mask) ? path_below :
not_public_path);
}
// __base_class_type_info::search2
// This is a psuedo-node which does nothing but adjust the path access and
// dynamic_ptr prior to calling the base node above.
// The dynamic_ptr adjustment depends upon whether or not this node is marked
// virtual.
// If the path up is public, no change is made to the path (it may already be
// marked private from below). If the path up is private, it is forced so.
int
__base_class_type_info::search2(__dynamic_cast_info* info, const void* dynamic_ptr,
int path_below) const
@ -347,7 +385,7 @@ __base_class_type_info::search2(__dynamic_cast_info* info, const void* dynamic_p
if (__offset_flags & __virtual_mask)
{
char* vtable = *(char**)dynamic_ptr;
offset_to_base = (ptrdiff_t)vtable[offset_to_base];
offset_to_base = *(ptrdiff_t*)(vtable + offset_to_base);
}
return __base_type->search2(info, (char*)dynamic_ptr + offset_to_base,
(__offset_flags & __public_mask) ? path_below :
@ -378,7 +416,7 @@ __base_class_type_info::display(const void* obj) const
if (__offset_flags & __virtual_mask)
{
char* vtable = *(char**)obj;
offset_to_base = (ptrdiff_t)vtable[offset_to_base];
offset_to_base = *(ptrdiff_t*)(vtable + offset_to_base);
}
__base_type->display((char*)obj + offset_to_base);
}
@ -426,7 +464,7 @@ __pointer_to_member_type_info::~__pointer_to_member_type_info()
// ambiguity, or
// 3. nullptr
// Knowns:
// (dynamic_ptr, dynamic_type) can be derived from static_ptr.
// (dynamic_ptr, dynamic_type) can be extracted from static_ptr.
// dynamic_ptr is a pointer to the complete run time object.
// dynamic_type is the type of the complete run time object.
// The type hierarchy is a DAG rooted at (dynamic_ptr, dynamic_type) and
@ -448,6 +486,27 @@ __pointer_to_member_type_info::~__pointer_to_member_type_info()
// (dynamic_ptr, dynamic_type) to (static_ptr, static_type),
// else returns nullptr.
// This check is purely an optimization and does not impact correctness.
// Algorithm:
// Extract (dynamic_ptr, dynamic_type) from static_ptr.
// If dynamic_type == dst_type
// If there is a public path from (dynamic_ptr, dynamic_type) to
// (static_ptr, static_type), return dynamic_ptr else return nullptr.
// Else dynamic_type != dst_type
// If there is a single dst_type derived (below) (static_ptr, static_type)
// If the path from that unique dst_type to (static_ptr, static_type)
// is public, return a pointer to that dst_type else return nullptr.
// Else if there are no dst_type's which don't point to (static_ptr, static_type)
// and if there is a pubic path from (dynamic_ptr, dynamic_type) to
// (static_ptr, static_type) and a public path from (dynamic_ptr, dynamic_type)
// to the single dst_type, then return a pointer to that dst_type,
// Else return nullptr.
// Else if there are no dst_type derived (below) (static_ptr, static_type)
// And if there is a single dst_type base of (above)
// (dynamic_ptr, dynamic_type), and if that single dst_type has a
// public path to it. And if there is a public path
// from (dynamic_ptr, dynamic_type) to (static_ptr, static_type)
// then return a pointer to that single dst_type, else return nullptr.
// Else return nullptr.
extern "C"
void*
__dynamic_cast(const void* static_ptr,
@ -487,7 +546,13 @@ dynamic_type->display(dynamic_ptr);
dst_ptr = info.dst_ptr_not_leading_to_static_ptr;
break;
case 1:
if (info.path_dst_ptr_to_static_ptr == public_path)
if (info.path_dst_ptr_to_static_ptr == public_path ||
(
info.number_to_dst_ptr == 0 &&
info.path_dynamic_ptr_to_static_ptr == public_path &&
info.path_dynamic_ptr_to_dst_ptr == public_path
)
)
dst_ptr = info.dst_ptr_leading_to_static_ptr;
break;
}

2453
libcxxabi/test/dynamic_cast3.cpp Normal file
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