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c-typeck.c (convert_for_assignment): Bring back conversion to union without a cast... 

* c-typeck.c (convert_for_assignment):
Bring back conversion to union without a cast,
undoing the Jan 16 change, but with the following differences:

* The union must have the transparent_union attribute.
* The conversion must be for a function argument.
* Warn consistently about such conversions if pedantic.
* Do not warn about an assignment incompatibility for one union member
  if another union member is compatible with no warning.

From-SVN: r11290
This commit is contained in:
Paul Eggert 1996-02-16 20:13:23 +00:00
parent 0afeb08a70
commit 7e842ef8c5
1 changed files with 105 additions and 0 deletions
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105
gcc/c-typeck.c
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@ -3996,6 +3996,111 @@ convert_for_assignment (type, rhs, errtype, fundecl, funname, parmnum)
|| coder == COMPLEX_TYPE))
return convert_and_check (type, rhs);
/* Conversion to a transparent union from its member types.
This applies only to function arguments. */
else if (codel == UNION_TYPE && TYPE_TRANSPARENT_UNION (type) && ! errtype)
{
tree memb_types;
tree marginal_memb_type = 0;
for (memb_types = TYPE_FIELDS (type); memb_types;
memb_types = TREE_CHAIN (memb_types))
{
tree memb_type = TREE_TYPE (memb_types);
if (comptypes (TYPE_MAIN_VARIANT (memb_type),
TYPE_MAIN_VARIANT (rhstype)))
break;
if (TREE_CODE (memb_type) != POINTER_TYPE)
continue;
if (coder == POINTER_TYPE)
{
register tree ttl = TREE_TYPE (memb_type);
register tree ttr = TREE_TYPE (rhstype);
/* Any non-function converts to a [const][volatile] void *
and vice versa; otherwise, targets must be the same.
Meanwhile, the lhs target must have all the qualifiers of
the rhs. */
if (TYPE_MAIN_VARIANT (ttl) == void_type_node
|| TYPE_MAIN_VARIANT (ttr) == void_type_node
|| comp_target_types (memb_type, rhstype))
{
/* If this type won't generate any warnings, use it. */
if ((TREE_CODE (ttr) == FUNCTION_TYPE
&& TREE_CODE (ttl) == FUNCTION_TYPE)
? ((! TYPE_READONLY (ttl) | TYPE_READONLY (ttr))
& (! TYPE_VOLATILE (ttl) | TYPE_VOLATILE (ttr)))
: ((TYPE_READONLY (ttl) | ! TYPE_READONLY (ttr))
& (TYPE_VOLATILE (ttl) | ! TYPE_VOLATILE (ttr))))
break;
/* Keep looking for a better type, but remember this one. */
if (! marginal_memb_type)
marginal_memb_type = memb_type;
}
}
/* Can convert integer zero to any pointer type. */
if (integer_zerop (rhs)
|| (TREE_CODE (rhs) == NOP_EXPR
&& integer_zerop (TREE_OPERAND (rhs, 0))))
{
rhs = null_pointer_node;
break;
}
}
if (memb_types || marginal_memb_type)
{
if (! memb_types)
{
/* We have only a marginally acceptable member type;
it needs a warning. */
register tree ttl = TREE_TYPE (marginal_memb_type);
register tree ttr = TREE_TYPE (rhstype);
/* Const and volatile mean something different for function
types, so the usual warnings are not appropriate. */
if (TREE_CODE (ttr) == FUNCTION_TYPE
&& TREE_CODE (ttl) == FUNCTION_TYPE)
{
/* Because const and volatile on functions are
restrictions that say the function will not do
certain things, it is okay to use a const or volatile
function where an ordinary one is wanted, but not
vice-versa. */
if (TYPE_READONLY (ttl) && ! TYPE_READONLY (ttr))
warn_for_assignment ("%s makes `const *' function pointer from non-const",
get_spelling (errtype), funname,
parmnum);
if (TYPE_VOLATILE (ttl) && ! TYPE_VOLATILE (ttr))
warn_for_assignment ("%s makes `volatile *' function pointer from non-volatile",
get_spelling (errtype), funname,
parmnum);
}
else
{
if (! TYPE_READONLY (ttl) && TYPE_READONLY (ttr))
warn_for_assignment ("%s discards `const' from pointer target type",
get_spelling (errtype), funname,
parmnum);
if (! TYPE_VOLATILE (ttl) && TYPE_VOLATILE (ttr))
warn_for_assignment ("%s discards `volatile' from pointer target type",
get_spelling (errtype), funname,
parmnum);
}
}
if (pedantic && ! DECL_IN_SYSTEM_HEADER (fundecl))
pedwarn ("ANSI C prohibits argument conversion to union type");
return build1 (NOP_EXPR, type, rhs);
}
}
/* Conversions among pointers */
else if (codel == POINTER_TYPE && coder == POINTER_TYPE)
{