On Thu, May 01, 2014 at 10:54:18PM +0000, Joseph S. Myers wrote: > I think the comment on this function should be updated to explain the > interface contract when an incomplete (or function) type is passed (i.e. > return size_one_node, caller is responsible for any diagnostics). Done.
> The test should I think also cover incomplete union types, and pointer > subtraction for all the different cases of incomplete types, and the += > and -= operators (i.e. cover invalid arithmetic on pointers to incomplete > types more thoroughly, even if not actually affected by this patch). Done. Another change is that I used COMPLETE_TYPE_P instead of COMPLETE_OR_VOID_TYPE_P, that would be a bug and before it didn't make much sense: we checked VOID_TYPE before. Tested x86_64-linux, ok now? 2014-05-02 Marek Polacek <pola...@redhat.com> PR c/25801 * c-typeck.c (c_size_in_bytes): Update comment. Don't call error. Return size_one_node when the type is not complete. (pointer_diff): Remove comment. (build_unary_op): Improve error messages. * gcc.dg/pr25801.c: New test. diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c index 98567b4..41770bc 100644 --- gcc/c/c-typeck.c +++ gcc/c/c-typeck.c @@ -1754,22 +1754,20 @@ type_lists_compatible_p (const_tree args1, const_tree args2, } } -/* Compute the size to increment a pointer by. */ +/* Compute the size to increment a pointer by. When a function type or void + type or incomplete type is passed, size_one_node is returned. + This function does not emit any diagnostics; the caller is responsible + for that. */ static tree c_size_in_bytes (const_tree type) { enum tree_code code = TREE_CODE (type); - if (code == FUNCTION_TYPE || code == VOID_TYPE || code == ERROR_MARK) + if (code == FUNCTION_TYPE || code == VOID_TYPE || code == ERROR_MARK + || !COMPLETE_TYPE_P (type)) return size_one_node; - if (!COMPLETE_OR_VOID_TYPE_P (type)) - { - error ("arithmetic on pointer to an incomplete type"); - return size_one_node; - } - /* Convert in case a char is more than one unit. */ return size_binop_loc (input_location, CEIL_DIV_EXPR, TYPE_SIZE_UNIT (type), size_int (TYPE_PRECISION (char_type_node) @@ -3530,7 +3528,6 @@ pointer_diff (location_t loc, tree op0, tree op1) if (!COMPLETE_OR_VOID_TYPE_P (TREE_TYPE (TREE_TYPE (orig_op1)))) error_at (loc, "arithmetic on pointer to an incomplete type"); - /* This generates an error if op0 is pointer to incomplete type. */ op1 = c_size_in_bytes (target_type); if (pointer_to_zero_sized_aggr_p (TREE_TYPE (orig_op1))) @@ -4004,16 +4001,18 @@ build_unary_op (location_t location, if (typecode == POINTER_TYPE) { - /* If pointer target is an undefined struct, + /* If pointer target is an incomplete type, we just cannot know how to do the arithmetic. */ if (!COMPLETE_OR_VOID_TYPE_P (TREE_TYPE (argtype))) { if (code == PREINCREMENT_EXPR || code == POSTINCREMENT_EXPR) error_at (location, - "increment of pointer to unknown structure"); + "increment of pointer to an incomplete type %qT", + TREE_TYPE (argtype)); else error_at (location, - "decrement of pointer to unknown structure"); + "decrement of pointer to an incomplete type %qT", + TREE_TYPE (argtype)); } else if (TREE_CODE (TREE_TYPE (argtype)) == FUNCTION_TYPE || TREE_CODE (TREE_TYPE (argtype)) == VOID_TYPE) diff --git gcc/testsuite/gcc.dg/pr25801.c gcc/testsuite/gcc.dg/pr25801.c index e69de29..10b53d3 100644 --- gcc/testsuite/gcc.dg/pr25801.c +++ gcc/testsuite/gcc.dg/pr25801.c @@ -0,0 +1,44 @@ +/* PR c/25801 */ +/* { dg-do compile } */ +/* { dg-options "-std=c99" } */ + +int (*a)[]; +struct S *s; +union U *u; +enum E *e; + +void +f (void) +{ + a++; /* { dg-error "increment of pointer to an incomplete type" } */ + ++a; /* { dg-error "increment of pointer to an incomplete type" } */ + a--; /* { dg-error "decrement of pointer to an incomplete type" } */ + --a; /* { dg-error "decrement of pointer to an incomplete type" } */ + a += 1; /* { dg-error "invalid use of array with unspecified bounds" } */ + a -= 1; /* { dg-error "invalid use of array with unspecified bounds" } */ + a - a; /* { dg-error "arithmetic on pointer to an incomplete type" } */ + + s++; /* { dg-error "increment of pointer to an incomplete type" } */ + ++s; /* { dg-error "increment of pointer to an incomplete type" } */ + s--; /* { dg-error "decrement of pointer to an incomplete type" } */ + --s; /* { dg-error "decrement of pointer to an incomplete type" } */ + s += 1; /* { dg-error "invalid use of undefined type" } */ + s -= 1; /* { dg-error "invalid use of undefined type" } */ + s - s; /* { dg-error "arithmetic on pointer to an incomplete type" } */ + + u++; /* { dg-error "increment of pointer to an incomplete type" } */ + ++u; /* { dg-error "increment of pointer to an incomplete type" } */ + u--; /* { dg-error "decrement of pointer to an incomplete type" } */ + --u; /* { dg-error "decrement of pointer to an incomplete type" } */ + u += 1; /* { dg-error "invalid use of undefined type" } */ + u -= 1; /* { dg-error "invalid use of undefined type" } */ + u - u; /* { dg-error "arithmetic on pointer to an incomplete type" } */ + + e++; /* { dg-error "increment of pointer to an incomplete type" } */ + ++e; /* { dg-error "increment of pointer to an incomplete type" } */ + e--; /* { dg-error "decrement of pointer to an incomplete type" } */ + --e; /* { dg-error "decrement of pointer to an incomplete type" } */ + e += 1; /* { dg-error "invalid use of undefined type" } */ + e -= 1; /* { dg-error "invalid use of undefined type" } */ + e - e; /* { dg-error "arithmetic on pointer to an incomplete type" } */ +} Marek