1 /* Array bounds checking.
2 Copyright (C) 2005-2021 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
11 GCC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
22 #include "coretypes.h"
27 #include "gimple-array-bounds.h"
28 #include "gimple-iterator.h"
29 #include "gimple-walk.h"
31 #include "fold-const.h"
32 #include "diagnostic-core.h"
35 #include "alloc-pool.h"
36 #include "vr-values.h"
42 // This purposely returns a value_range, not a value_range_equiv, to
43 // break the dependency on equivalences for this pass.
46 array_bounds_checker::get_value_range (const_tree op
)
48 return ranges
->get_value_range (op
);
51 /* Try to determine the DECL that REF refers to. Return the DECL or
52 the expression closest to it. Used in informational notes pointing
53 to referenced objects or function parameters. */
56 get_base_decl (tree ref
)
58 tree base
= get_base_address (ref
);
62 if (TREE_CODE (base
) == MEM_REF
)
63 base
= TREE_OPERAND (base
, 0);
65 if (TREE_CODE (base
) != SSA_NAME
)
70 gimple
*def
= SSA_NAME_DEF_STMT (base
);
71 if (gimple_assign_single_p (def
))
73 base
= gimple_assign_rhs1 (def
);
74 if (TREE_CODE (base
) != ASSERT_EXPR
)
77 base
= TREE_OPERAND (base
, 0);
78 if (TREE_CODE (base
) != SSA_NAME
)
84 if (!gimple_nop_p (def
))
90 tree var
= SSA_NAME_VAR (base
);
91 if (TREE_CODE (var
) != PARM_DECL
)
97 /* Return the constant byte size of the object or type referenced by
98 the MEM_REF ARG. On success, set *PREF to the DECL or expression
99 ARG refers to. Otherwise return null. */
102 get_ref_size (tree arg
, tree
*pref
)
104 if (TREE_CODE (arg
) != MEM_REF
)
107 arg
= TREE_OPERAND (arg
, 0);
108 tree type
= TREE_TYPE (arg
);
109 if (!POINTER_TYPE_P (type
))
112 type
= TREE_TYPE (type
);
113 if (TREE_CODE (type
) != ARRAY_TYPE
)
116 tree nbytes
= TYPE_SIZE_UNIT (type
);
117 if (!nbytes
|| TREE_CODE (nbytes
) != INTEGER_CST
)
120 *pref
= get_base_decl (arg
);
124 /* Return true if REF is (likely) an ARRAY_REF to a trailing array member
125 of a struct. It refines array_at_struct_end_p by detecting a pointer
126 to an array and an array parameter declared using the [N] syntax (as
127 opposed to a pointer) and returning false. Set *PREF to the decl or
128 expression REF refers to. */
131 trailing_array (tree arg
, tree
*pref
)
134 tree base
= get_base_decl (arg
);
135 while (TREE_CODE (ref
) == ARRAY_REF
|| TREE_CODE (ref
) == MEM_REF
)
136 ref
= TREE_OPERAND (ref
, 0);
138 if (TREE_CODE (ref
) == COMPONENT_REF
)
140 *pref
= TREE_OPERAND (ref
, 1);
141 tree type
= TREE_TYPE (*pref
);
142 if (TREE_CODE (type
) == ARRAY_TYPE
)
144 /* A multidimensional trailing array is not considered special
145 no matter what its major bound is. */
146 type
= TREE_TYPE (type
);
147 if (TREE_CODE (type
) == ARRAY_TYPE
)
154 tree basetype
= TREE_TYPE (base
);
155 if (TREE_CODE (base
) == PARM_DECL
156 && POINTER_TYPE_P (basetype
))
158 tree ptype
= TREE_TYPE (basetype
);
159 if (TREE_CODE (ptype
) == ARRAY_TYPE
)
163 return array_at_struct_end_p (arg
);
166 /* Checks one ARRAY_REF in REF, located at LOCUS. Ignores flexible
167 arrays and "struct" hacks. If VRP can determine that the array
168 subscript is a constant, check if it is outside valid range. If
169 the array subscript is a RANGE, warn if it is non-overlapping with
170 valid range. IGNORE_OFF_BY_ONE is true if the ARRAY_REF is inside
171 a ADDR_EXPR. Return true if a warning has been issued or if
172 no-warning is set. */
175 array_bounds_checker::check_array_ref (location_t location
, tree ref
,
176 bool ignore_off_by_one
)
178 if (TREE_NO_WARNING (ref
))
179 /* Return true to have the caller prevent warnings for enclosing
183 tree low_sub
= TREE_OPERAND (ref
, 1);
184 tree up_sub
= low_sub
;
185 tree up_bound
= array_ref_up_bound (ref
);
187 /* Referenced decl if one can be determined. */
188 tree decl
= NULL_TREE
;
190 /* Set for accesses to interior zero-length arrays. */
191 special_array_member sam
{ };
196 || TREE_CODE (up_bound
) != INTEGER_CST
197 || (warn_array_bounds
< 2 && trailing_array (ref
, &decl
)))
199 /* Accesses to trailing arrays via pointers may access storage
200 beyond the types array bounds. For such arrays, or for flexible
201 array members, as well as for other arrays of an unknown size,
202 replace the upper bound with a more permissive one that assumes
203 the size of the largest object is PTRDIFF_MAX. */
204 tree eltsize
= array_ref_element_size (ref
);
206 if (TREE_CODE (eltsize
) != INTEGER_CST
207 || integer_zerop (eltsize
))
209 up_bound
= NULL_TREE
;
210 up_bound_p1
= NULL_TREE
;
214 tree ptrdiff_max
= TYPE_MAX_VALUE (ptrdiff_type_node
);
215 tree maxbound
= ptrdiff_max
;
216 tree arg
= TREE_OPERAND (ref
, 0);
218 const bool compref
= TREE_CODE (arg
) == COMPONENT_REF
;
221 /* Try to determine the size of the trailing array from
222 its initializer (if it has one). */
223 if (tree refsize
= component_ref_size (arg
, &sam
))
224 if (TREE_CODE (refsize
) == INTEGER_CST
)
228 if (maxbound
== ptrdiff_max
)
230 /* Try to determine the size of the base object. Avoid
231 COMPONENT_REF already tried above. Using its DECL_SIZE
232 size wouldn't necessarily be correct if the reference is
233 to its flexible array member initialized in a different
236 if (tree base
= get_addr_base_and_unit_offset (arg
, &off
))
238 if (TREE_CODE (base
) == MEM_REF
)
240 /* Try to determine the size from a pointer to
241 an array if BASE is one. */
242 if (tree size
= get_ref_size (base
, &decl
))
245 else if (!compref
&& DECL_P (base
))
246 if (tree basesize
= DECL_SIZE_UNIT (base
))
247 if (TREE_CODE (basesize
) == INTEGER_CST
)
253 if (known_gt (off
, 0))
254 maxbound
= wide_int_to_tree (sizetype
,
255 wi::sub (wi::to_wide (maxbound
),
260 maxbound
= fold_convert (sizetype
, maxbound
);
262 up_bound_p1
= int_const_binop (TRUNC_DIV_EXPR
, maxbound
, eltsize
);
264 if (up_bound_p1
!= NULL_TREE
)
265 up_bound
= int_const_binop (MINUS_EXPR
, up_bound_p1
,
266 build_int_cst (ptrdiff_type_node
, 1));
268 up_bound
= NULL_TREE
;
272 up_bound_p1
= int_const_binop (PLUS_EXPR
, up_bound
,
273 build_int_cst (TREE_TYPE (up_bound
), 1));
275 tree low_bound
= array_ref_low_bound (ref
);
277 tree artype
= TREE_TYPE (TREE_OPERAND (ref
, 0));
282 if (up_bound
&& tree_int_cst_equal (low_bound
, up_bound_p1
))
283 warned
= warning_at (location
, OPT_Warray_bounds
,
284 "array subscript %E is outside array bounds of %qT",
287 const value_range
*vr
= NULL
;
288 if (TREE_CODE (low_sub
) == SSA_NAME
)
290 vr
= get_value_range (low_sub
);
291 if (!vr
->undefined_p () && !vr
->varying_p ())
293 low_sub
= vr
->kind () == VR_RANGE
? vr
->max () : vr
->min ();
294 up_sub
= vr
->kind () == VR_RANGE
? vr
->min () : vr
->max ();
300 else if (vr
&& vr
->kind () == VR_ANTI_RANGE
)
303 && TREE_CODE (up_sub
) == INTEGER_CST
304 && (ignore_off_by_one
305 ? tree_int_cst_lt (up_bound
, up_sub
)
306 : tree_int_cst_le (up_bound
, up_sub
))
307 && TREE_CODE (low_sub
) == INTEGER_CST
308 && tree_int_cst_le (low_sub
, low_bound
))
309 warned
= warning_at (location
, OPT_Warray_bounds
,
310 "array subscript [%E, %E] is outside "
311 "array bounds of %qT",
312 low_sub
, up_sub
, artype
);
315 && TREE_CODE (up_sub
) == INTEGER_CST
316 && (ignore_off_by_one
317 ? !tree_int_cst_le (up_sub
, up_bound_p1
)
318 : !tree_int_cst_le (up_sub
, up_bound
)))
319 warned
= warning_at (location
, OPT_Warray_bounds
,
320 "array subscript %E is above array bounds of %qT",
322 else if (TREE_CODE (low_sub
) == INTEGER_CST
323 && tree_int_cst_lt (low_sub
, low_bound
))
324 warned
= warning_at (location
, OPT_Warray_bounds
,
325 "array subscript %E is below array bounds of %qT",
328 if (!warned
&& sam
== special_array_member::int_0
)
329 warned
= warning_at (location
, OPT_Wzero_length_bounds
,
330 (TREE_CODE (low_sub
) == INTEGER_CST
331 ? G_("array subscript %E is outside the bounds "
332 "of an interior zero-length array %qT")
333 : G_("array subscript %qE is outside the bounds "
334 "of an interior zero-length array %qT")),
339 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
341 fprintf (dump_file
, "Array bound warning for ");
342 dump_generic_expr (MSG_NOTE
, TDF_SLIM
, ref
);
343 fprintf (dump_file
, "\n");
346 /* Avoid more warnings when checking more significant subscripts
347 of the same expression. */
348 ref
= TREE_OPERAND (ref
, 0);
349 TREE_NO_WARNING (ref
) = 1;
354 tree rec
= NULL_TREE
;
355 if (TREE_CODE (ref
) == COMPONENT_REF
)
357 /* For a reference to a member of a struct object also mention
358 the object if it's known. It may be defined in a different
359 function than the out-of-bounds access. */
360 rec
= TREE_OPERAND (ref
, 0);
363 ref
= TREE_OPERAND (ref
, 1);
367 inform (DECL_SOURCE_LOCATION (ref
), "while referencing %qD", ref
);
368 if (rec
&& DECL_P (rec
))
369 inform (DECL_SOURCE_LOCATION (rec
), "defined here %qD", rec
);
375 /* Wrapper around build_array_type_nelts that makes sure the array
376 can be created at all and handles zero sized arrays specially. */
379 build_printable_array_type (tree eltype
, unsigned HOST_WIDE_INT nelts
)
381 if (TYPE_SIZE_UNIT (eltype
)
382 && TREE_CODE (TYPE_SIZE_UNIT (eltype
)) == INTEGER_CST
383 && !integer_zerop (TYPE_SIZE_UNIT (eltype
))
384 && TYPE_ALIGN_UNIT (eltype
) > 1
385 && wi::zext (wi::to_wide (TYPE_SIZE_UNIT (eltype
)),
386 ffs_hwi (TYPE_ALIGN_UNIT (eltype
)) - 1) != 0)
387 eltype
= TYPE_MAIN_VARIANT (eltype
);
390 return build_array_type_nelts (eltype
, nelts
);
392 tree idxtype
= build_range_type (sizetype
, size_zero_node
, NULL_TREE
);
393 tree arrtype
= build_array_type (eltype
, idxtype
);
394 arrtype
= build_distinct_type_copy (TYPE_MAIN_VARIANT (arrtype
));
395 TYPE_SIZE (arrtype
) = bitsize_zero_node
;
396 TYPE_SIZE_UNIT (arrtype
) = size_zero_node
;
400 /* Checks one MEM_REF in REF, located at LOCATION, for out-of-bounds
401 references to string constants. If VRP can determine that the array
402 subscript is a constant, check if it is outside valid range.
403 If the array subscript is a RANGE, warn if it is non-overlapping
405 IGNORE_OFF_BY_ONE is true if the MEM_REF is inside an ADDR_EXPR
406 (used to allow one-past-the-end indices for code that takes
407 the address of the just-past-the-end element of an array).
408 Returns true if a warning has been issued. */
411 array_bounds_checker::check_mem_ref (location_t location
, tree ref
,
412 bool ignore_off_by_one
)
414 if (TREE_NO_WARNING (ref
))
417 tree arg
= TREE_OPERAND (ref
, 0);
418 /* The constant and variable offset of the reference. */
419 tree cstoff
= TREE_OPERAND (ref
, 1);
420 tree varoff
= NULL_TREE
;
422 const offset_int maxobjsize
= tree_to_shwi (max_object_size ());
424 /* The zero-based array or string constant bounds in bytes. Initially
425 set to [-MAXOBJSIZE - 1, MAXOBJSIZE] until a tighter bound is
427 offset_int arrbounds
[2] = { -maxobjsize
- 1, maxobjsize
};
429 /* The minimum and maximum intermediate offset. For a reference
430 to be valid, not only does the final offset/subscript must be
431 in bounds but all intermediate offsets should be as well.
432 GCC may be able to deal gracefully with such out-of-bounds
433 offsets so the checking is only enabled at -Warray-bounds=2
434 where it may help detect bugs in uses of the intermediate
435 offsets that could otherwise not be detectable. */
436 offset_int ioff
= wi::to_offset (fold_convert (ptrdiff_type_node
, cstoff
));
437 offset_int extrema
[2] = { 0, wi::abs (ioff
) };
439 /* The range of the byte offset into the reference. */
440 offset_int offrange
[2] = { 0, 0 };
442 /* The statement used to allocate the array or null. */
443 gimple
*alloc_stmt
= NULL
;
444 /* For an allocation statement, the low bound of the size range. */
445 offset_int minbound
= 0;
447 /* Determine the offsets and increment OFFRANGE for the bounds of each.
448 The loop computes the range of the final offset for expressions such
449 as (A + i0 + ... + iN)[CSTOFF] where i0 through iN are SSA_NAMEs in
451 const unsigned limit
= param_ssa_name_def_chain_limit
;
452 for (unsigned n
= 0; TREE_CODE (arg
) == SSA_NAME
&& n
< limit
; ++n
)
454 gimple
*def
= SSA_NAME_DEF_STMT (arg
);
455 if (is_gimple_call (def
))
457 /* Determine the byte size of the array from an allocation call. */
459 if (gimple_call_alloc_size (def
, sizrng
))
462 arrbounds
[1] = offset_int::from (sizrng
[1], UNSIGNED
);
463 minbound
= offset_int::from (sizrng
[0], UNSIGNED
);
469 if (gimple_nop_p (def
))
471 /* For a function argument try to determine the byte size
472 of the array from the current function declaratation
473 (e.g., attribute access or related). */
475 tree ref
= gimple_parm_array_size (arg
, wr
);
478 arrbounds
[0] = offset_int::from (wr
[0], UNSIGNED
);
479 arrbounds
[1] = offset_int::from (wr
[1], UNSIGNED
);
484 if (!is_gimple_assign (def
))
487 tree_code code
= gimple_assign_rhs_code (def
);
488 if (code
== POINTER_PLUS_EXPR
)
490 arg
= gimple_assign_rhs1 (def
);
491 varoff
= gimple_assign_rhs2 (def
);
493 else if (code
== ASSERT_EXPR
)
495 arg
= TREE_OPERAND (gimple_assign_rhs1 (def
), 0);
501 /* VAROFF should always be a SSA_NAME here (and not even
502 INTEGER_CST) but there's no point in taking chances. */
503 if (TREE_CODE (varoff
) != SSA_NAME
)
506 const value_range
* const vr
= get_value_range (varoff
);
507 if (!vr
|| vr
->undefined_p () || vr
->varying_p ())
510 if (!vr
->constant_p ())
513 if (vr
->kind () == VR_RANGE
)
516 = wi::to_offset (fold_convert (ptrdiff_type_node
, vr
->min ()));
518 = wi::to_offset (fold_convert (ptrdiff_type_node
, vr
->max ()));
526 /* When MIN >= MAX, the offset is effectively in a union
527 of two ranges: [-MAXOBJSIZE -1, MAX] and [MIN, MAXOBJSIZE].
528 Since there is no way to represent such a range across
529 additions, conservatively add [-MAXOBJSIZE -1, MAXOBJSIZE]
531 offrange
[0] += arrbounds
[0];
532 offrange
[1] += arrbounds
[1];
537 /* For an anti-range, analogously to the above, conservatively
538 add [-MAXOBJSIZE -1, MAXOBJSIZE] to OFFRANGE. */
539 offrange
[0] += arrbounds
[0];
540 offrange
[1] += arrbounds
[1];
543 /* Keep track of the minimum and maximum offset. */
544 if (offrange
[1] < 0 && offrange
[1] < extrema
[0])
545 extrema
[0] = offrange
[1];
546 if (offrange
[0] > 0 && offrange
[0] > extrema
[1])
547 extrema
[1] = offrange
[0];
549 if (offrange
[0] < arrbounds
[0])
550 offrange
[0] = arrbounds
[0];
552 if (offrange
[1] > arrbounds
[1])
553 offrange
[1] = arrbounds
[1];
556 tree reftype
= NULL_TREE
;
557 offset_int eltsize
= -1;
558 if (arrbounds
[0] >= 0)
560 /* The byte size of the array has already been determined above
561 based on a pointer ARG. Set ELTSIZE to the size of the type
562 it points to and REFTYPE to the array with the size, rounded
563 down as necessary. */
564 reftype
= TREE_TYPE (TREE_TYPE (arg
));
565 if (TREE_CODE (reftype
) == ARRAY_TYPE
)
566 reftype
= TREE_TYPE (reftype
);
567 if (tree refsize
= TYPE_SIZE_UNIT (reftype
))
568 if (TREE_CODE (refsize
) == INTEGER_CST
)
569 eltsize
= wi::to_offset (refsize
);
574 offset_int nelts
= arrbounds
[1] / eltsize
;
575 reftype
= build_printable_array_type (reftype
, nelts
.to_uhwi ());
577 else if (TREE_CODE (arg
) == ADDR_EXPR
)
579 arg
= TREE_OPERAND (arg
, 0);
580 if (TREE_CODE (arg
) != STRING_CST
581 && TREE_CODE (arg
) != PARM_DECL
582 && TREE_CODE (arg
) != VAR_DECL
)
585 /* The type of the object being referred to. It can be an array,
586 string literal, or a non-array type when the MEM_REF represents
587 a reference/subscript via a pointer to an object that is not
588 an element of an array. Incomplete types are excluded as well
589 because their size is not known. */
590 reftype
= TREE_TYPE (arg
);
591 if (POINTER_TYPE_P (reftype
)
592 || !COMPLETE_TYPE_P (reftype
)
593 || TREE_CODE (TYPE_SIZE_UNIT (reftype
)) != INTEGER_CST
)
596 /* Except in declared objects, references to trailing array members
597 of structs and union objects are excluded because MEM_REF doesn't
598 make it possible to identify the member where the reference
600 if (RECORD_OR_UNION_TYPE_P (reftype
)
602 || (DECL_EXTERNAL (arg
) && array_at_struct_end_p (ref
))))
605 /* FIXME: Should this be 1 for Fortran? */
608 if (TREE_CODE (reftype
) == ARRAY_TYPE
)
610 /* Set to the size of the array element (and adjust below). */
611 eltsize
= wi::to_offset (TYPE_SIZE_UNIT (TREE_TYPE (reftype
)));
612 /* Use log2 of size to convert the array byte size in to its
613 upper bound in elements. */
614 const offset_int eltsizelog2
= wi::floor_log2 (eltsize
);
615 if (tree dom
= TYPE_DOMAIN (reftype
))
617 tree bnds
[] = { TYPE_MIN_VALUE (dom
), TYPE_MAX_VALUE (dom
) };
618 if (TREE_CODE (arg
) == COMPONENT_REF
)
620 offset_int size
= maxobjsize
;
621 if (tree fldsize
= component_ref_size (arg
))
622 size
= wi::to_offset (fldsize
);
623 arrbounds
[1] = wi::lrshift (size
, eltsizelog2
);
625 else if (array_at_struct_end_p (arg
) || !bnds
[0] || !bnds
[1])
626 arrbounds
[1] = wi::lrshift (maxobjsize
, eltsizelog2
);
628 arrbounds
[1] = (wi::to_offset (bnds
[1]) - wi::to_offset (bnds
[0])
632 arrbounds
[1] = wi::lrshift (maxobjsize
, eltsizelog2
);
634 /* Determine a tighter bound of the non-array element type. */
635 tree eltype
= TREE_TYPE (reftype
);
636 while (TREE_CODE (eltype
) == ARRAY_TYPE
)
637 eltype
= TREE_TYPE (eltype
);
638 eltsize
= wi::to_offset (TYPE_SIZE_UNIT (eltype
));
643 tree size
= TYPE_SIZE_UNIT (reftype
);
645 if (tree initsize
= DECL_SIZE_UNIT (arg
))
646 if (tree_int_cst_lt (size
, initsize
))
649 arrbounds
[1] = wi::to_offset (size
);
658 /* Compute the more permissive upper bound when IGNORE_OFF_BY_ONE
659 is set (when taking the address of the one-past-last element
660 of an array) but always use the stricter bound in diagnostics. */
661 offset_int ubound
= arrbounds
[1];
662 if (ignore_off_by_one
)
666 /* Set if the lower bound of the subscript is out of bounds. */
667 const bool lboob
= (arrbounds
[0] == arrbounds
[1]
668 || offrange
[0] >= ubound
669 || offrange
[1] < arrbounds
[0]);
670 /* Set if only the upper bound of the subscript is out of bounds.
671 This can happen when using a bigger type to index into an array
672 of a smaller type, as is common with unsigned char. */
673 tree axstype
= TREE_TYPE (ref
);
674 offset_int axssize
= 0;
675 if (TREE_CODE (axstype
) != UNION_TYPE
)
676 if (tree access_size
= TYPE_SIZE_UNIT (axstype
))
677 if (TREE_CODE (access_size
) == INTEGER_CST
)
678 axssize
= wi::to_offset (access_size
);
680 const bool uboob
= !lboob
&& offrange
[0] + axssize
> ubound
;
683 /* Treat a reference to a non-array object as one to an array
684 of a single element. */
685 if (TREE_CODE (reftype
) != ARRAY_TYPE
)
686 reftype
= build_printable_array_type (reftype
, 1);
688 /* Extract the element type out of MEM_REF and use its size
689 to compute the index to print in the diagnostic; arrays
690 in MEM_REF don't mean anything. A type with no size like
691 void is as good as having a size of 1. */
692 tree type
= TREE_TYPE (ref
);
693 while (TREE_CODE (type
) == ARRAY_TYPE
)
694 type
= TREE_TYPE (type
);
695 if (tree size
= TYPE_SIZE_UNIT (type
))
697 offrange
[0] = offrange
[0] / wi::to_offset (size
);
698 offrange
[1] = offrange
[1] / wi::to_offset (size
);
704 if (offrange
[0] == offrange
[1])
705 warned
= warning_at (location
, OPT_Warray_bounds
,
706 "array subscript %wi is outside array bounds "
708 offrange
[0].to_shwi (), reftype
);
710 warned
= warning_at (location
, OPT_Warray_bounds
,
711 "array subscript [%wi, %wi] is outside "
712 "array bounds of %qT",
713 offrange
[0].to_shwi (),
714 offrange
[1].to_shwi (), reftype
);
716 else if (uboob
&& !ignore_off_by_one
)
718 tree backtype
= reftype
;
720 /* If the memory was dynamically allocated refer to it as if
721 it were an untyped array of bytes. */
722 backtype
= build_array_type_nelts (unsigned_char_type_node
,
723 arrbounds
[1].to_uhwi ());
725 warned
= warning_at (location
, OPT_Warray_bounds
,
726 "array subscript %<%T[%wi]%> is partly "
727 "outside array bounds of %qT",
728 axstype
, offrange
[0].to_shwi (), backtype
);
734 inform (DECL_SOURCE_LOCATION (arg
), "while referencing %qD", arg
);
737 location_t loc
= gimple_location (alloc_stmt
);
738 if (gimple_call_builtin_p (alloc_stmt
, BUILT_IN_ALLOCA_WITH_ALIGN
))
740 if (minbound
== arrbounds
[1])
741 inform (loc
, "referencing a variable length array "
742 "of size %wu", minbound
.to_uhwi ());
744 inform (loc
, "referencing a variable length array "
745 "of size between %wu and %wu",
746 minbound
.to_uhwi (), arrbounds
[1].to_uhwi ());
748 else if (tree fndecl
= gimple_call_fndecl (alloc_stmt
))
750 if (minbound
== arrbounds
[1])
751 inform (loc
, "referencing an object of size %wu "
753 minbound
.to_uhwi (), fndecl
);
755 inform (loc
, "referencing an object of size between "
756 "%wu and %wu allocated by %qD",
757 minbound
.to_uhwi (), arrbounds
[1].to_uhwi (), fndecl
);
761 tree fntype
= gimple_call_fntype (alloc_stmt
);
762 if (minbound
== arrbounds
[1])
763 inform (loc
, "referencing an object of size %wu "
765 minbound
.to_uhwi (), fntype
);
767 inform (loc
, "referencing an object of size between "
768 "%wu and %wu allocated by %qT",
769 minbound
.to_uhwi (), arrbounds
[1].to_uhwi (), fntype
);
773 TREE_NO_WARNING (ref
) = 1;
777 if (warn_array_bounds
< 2)
780 /* At level 2 check also intermediate offsets. */
782 if (extrema
[i
] < -arrbounds
[1] || extrema
[i
= 1] > ubound
)
784 HOST_WIDE_INT tmpidx
= extrema
[i
].to_shwi () / eltsize
.to_shwi ();
786 if (warning_at (location
, OPT_Warray_bounds
,
787 "intermediate array offset %wi is outside array bounds "
788 "of %qT", tmpidx
, reftype
))
790 TREE_NO_WARNING (ref
) = 1;
798 /* Searches if the expr T, located at LOCATION computes
799 address of an ARRAY_REF, and call check_array_ref on it. */
802 array_bounds_checker::check_addr_expr (location_t location
, tree t
)
804 /* For the most significant subscript only, accept taking the address
805 of the just-past-the-end element. */
806 bool ignore_off_by_one
= true;
808 /* Check each ARRAY_REF and MEM_REF in the reference chain. */
812 if (TREE_CODE (t
) == ARRAY_REF
)
814 warned
= check_array_ref (location
, t
, ignore_off_by_one
);
815 ignore_off_by_one
= false;
817 else if (TREE_CODE (t
) == MEM_REF
)
818 warned
= check_mem_ref (location
, t
, ignore_off_by_one
);
821 TREE_NO_WARNING (t
) = true;
823 t
= TREE_OPERAND (t
, 0);
825 while (handled_component_p (t
) || TREE_CODE (t
) == MEM_REF
);
827 if (TREE_CODE (t
) != MEM_REF
828 || TREE_CODE (TREE_OPERAND (t
, 0)) != ADDR_EXPR
829 || TREE_NO_WARNING (t
))
832 tree tem
= TREE_OPERAND (TREE_OPERAND (t
, 0), 0);
833 tree low_bound
, up_bound
, el_sz
;
834 if (TREE_CODE (TREE_TYPE (tem
)) != ARRAY_TYPE
835 || TREE_CODE (TREE_TYPE (TREE_TYPE (tem
))) == ARRAY_TYPE
836 || !TYPE_DOMAIN (TREE_TYPE (tem
)))
839 low_bound
= TYPE_MIN_VALUE (TYPE_DOMAIN (TREE_TYPE (tem
)));
840 up_bound
= TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (tem
)));
841 el_sz
= TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (tem
)));
843 || TREE_CODE (low_bound
) != INTEGER_CST
845 || TREE_CODE (up_bound
) != INTEGER_CST
847 || TREE_CODE (el_sz
) != INTEGER_CST
)
851 if (!mem_ref_offset (t
).is_constant (&idx
))
855 idx
= wi::sdiv_trunc (idx
, wi::to_offset (el_sz
));
858 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
860 fprintf (dump_file
, "Array bound warning for ");
861 dump_generic_expr (MSG_NOTE
, TDF_SLIM
, t
);
862 fprintf (dump_file
, "\n");
864 warned
= warning_at (location
, OPT_Warray_bounds
,
865 "array subscript %wi is below "
866 "array bounds of %qT",
867 idx
.to_shwi (), TREE_TYPE (tem
));
869 else if (idx
> (wi::to_offset (up_bound
)
870 - wi::to_offset (low_bound
) + 1))
872 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
874 fprintf (dump_file
, "Array bound warning for ");
875 dump_generic_expr (MSG_NOTE
, TDF_SLIM
, t
);
876 fprintf (dump_file
, "\n");
878 warned
= warning_at (location
, OPT_Warray_bounds
,
879 "array subscript %wu is above "
880 "array bounds of %qT",
881 idx
.to_uhwi (), TREE_TYPE (tem
));
887 inform (DECL_SOURCE_LOCATION (t
), "while referencing %qD", t
);
889 TREE_NO_WARNING (t
) = 1;
893 /* Return true if T is a reference to a member of a base class that's within
894 the bounds of the enclosing complete object. The function "hacks" around
895 problems discussed in pr98266 and pr97595. */
898 inbounds_memaccess_p (tree t
)
900 if (TREE_CODE (t
) != COMPONENT_REF
)
903 tree mref
= TREE_OPERAND (t
, 0);
904 if (TREE_CODE (mref
) != MEM_REF
)
907 /* Consider the access if its type is a derived class. */
908 tree mreftype
= TREE_TYPE (mref
);
909 if (!RECORD_OR_UNION_TYPE_P (mreftype
)
910 || !TYPE_BINFO (mreftype
))
913 /* Compute the size of the referenced object (it could be dynamically
915 access_ref aref
; // unused
916 tree refop
= TREE_OPERAND (mref
, 0);
917 tree refsize
= compute_objsize (refop
, 1, &aref
);
918 if (!refsize
|| TREE_CODE (refsize
) != INTEGER_CST
)
921 /* Compute the byte offset of the member within its enclosing class. */
922 tree fld
= TREE_OPERAND (t
, 1);
923 tree fldpos
= byte_position (fld
);
924 if (TREE_CODE (fldpos
) != INTEGER_CST
)
927 /* Compute the byte offset of the member with the outermost complete
928 object by adding its offset computed above to the MEM_REF offset. */
929 tree refoff
= TREE_OPERAND (mref
, 1);
930 tree fldoff
= int_const_binop (PLUS_EXPR
, fldpos
, refoff
);
931 /* Return false if the member offset is greater or equal to the size
932 of the complete object. */
933 if (!tree_int_cst_lt (fldoff
, refsize
))
936 tree fldsiz
= DECL_SIZE_UNIT (fld
);
937 if (!fldsiz
|| TREE_CODE (fldsiz
) != INTEGER_CST
)
940 /* Return true if the offset just past the end of the member is less
941 than or equal to the size of the complete object. */
942 tree fldend
= int_const_binop (PLUS_EXPR
, fldoff
, fldsiz
);
943 return tree_int_cst_le (fldend
, refsize
);
946 /* Callback for walk_tree to check a tree for out of bounds array
947 accesses. The array_bounds_checker class is passed in DATA. */
950 array_bounds_checker::check_array_bounds (tree
*tp
, int *walk_subtree
,
954 struct walk_stmt_info
*wi
= (struct walk_stmt_info
*) data
;
957 if (EXPR_HAS_LOCATION (t
))
958 location
= EXPR_LOCATION (t
);
960 location
= gimple_location (wi
->stmt
);
962 *walk_subtree
= TRUE
;
965 array_bounds_checker
*checker
= (array_bounds_checker
*) wi
->info
;
966 if (TREE_CODE (t
) == ARRAY_REF
)
967 warned
= checker
->check_array_ref (location
, t
,
968 false/*ignore_off_by_one*/);
969 else if (TREE_CODE (t
) == MEM_REF
)
970 warned
= checker
->check_mem_ref (location
, t
,
971 false /*ignore_off_by_one*/);
972 else if (TREE_CODE (t
) == ADDR_EXPR
)
974 checker
->check_addr_expr (location
, t
);
975 *walk_subtree
= false;
977 else if (inbounds_memaccess_p (t
))
978 /* Hack: Skip MEM_REF checks in accesses to a member of a base class
979 at an offset that's within the bounds of the enclosing object.
980 See pr98266 and pr97595. */
981 *walk_subtree
= false;
983 /* Propagate the no-warning bit to the outer expression. */
985 TREE_NO_WARNING (t
) = true;
990 /* A dom_walker subclass for use by check_all_array_refs, to walk over
991 all statements of all reachable BBs and call check_array_bounds on
994 class check_array_bounds_dom_walker
: public dom_walker
997 check_array_bounds_dom_walker (array_bounds_checker
*checker
)
998 : dom_walker (CDI_DOMINATORS
,
999 /* Discover non-executable edges, preserving EDGE_EXECUTABLE
1000 flags, so that we can merge in information on
1001 non-executable edges from vrp_folder . */
1002 REACHABLE_BLOCKS_PRESERVING_FLAGS
),
1003 checker (checker
) { }
1004 ~check_array_bounds_dom_walker () {}
1006 edge
before_dom_children (basic_block
) FINAL OVERRIDE
;
1009 array_bounds_checker
*checker
;
1012 /* Implementation of dom_walker::before_dom_children.
1014 Walk over all statements of BB and call check_array_bounds on them,
1015 and determine if there's a unique successor edge. */
1018 check_array_bounds_dom_walker::before_dom_children (basic_block bb
)
1020 gimple_stmt_iterator si
;
1021 for (si
= gsi_start_bb (bb
); !gsi_end_p (si
); gsi_next (&si
))
1023 gimple
*stmt
= gsi_stmt (si
);
1024 struct walk_stmt_info wi
;
1025 if (!gimple_has_location (stmt
)
1026 || is_gimple_debug (stmt
))
1029 memset (&wi
, 0, sizeof (wi
));
1033 walk_gimple_op (stmt
, array_bounds_checker::check_array_bounds
, &wi
);
1036 /* Determine if there's a unique successor edge, and if so, return
1037 that back to dom_walker, ensuring that we don't visit blocks that
1038 became unreachable during the VRP propagation
1039 (PR tree-optimization/83312). */
1040 return find_taken_edge (bb
, NULL_TREE
);
1044 array_bounds_checker::check ()
1046 check_array_bounds_dom_walker
w (this);
1047 w
.walk (ENTRY_BLOCK_PTR_FOR_FN (fun
));