| /* Array bounds checking. |
| Copyright (C) 2005-2021 Free Software Foundation, Inc. |
| |
| This file is part of GCC. |
| |
| GCC is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3, or (at your option) |
| any later version. |
| |
| GCC is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GCC; see the file COPYING3. If not see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "backend.h" |
| #include "tree.h" |
| #include "gimple.h" |
| #include "ssa.h" |
| #include "gimple-array-bounds.h" |
| #include "gimple-iterator.h" |
| #include "gimple-walk.h" |
| #include "tree-dfa.h" |
| #include "fold-const.h" |
| #include "diagnostic-core.h" |
| #include "intl.h" |
| #include "tree-vrp.h" |
| #include "alloc-pool.h" |
| #include "vr-values.h" |
| #include "domwalk.h" |
| #include "tree-cfg.h" |
| #include "attribs.h" |
| #include "pointer-query.h" |
| |
| // This purposely returns a value_range, not a value_range_equiv, to |
| // break the dependency on equivalences for this pass. |
| |
| const value_range * |
| array_bounds_checker::get_value_range (const_tree op, gimple *stmt) |
| { |
| return ranges->get_value_range (op, stmt); |
| } |
| |
| /* Try to determine the DECL that REF refers to. Return the DECL or |
| the expression closest to it. Used in informational notes pointing |
| to referenced objects or function parameters. */ |
| |
| static tree |
| get_base_decl (tree ref) |
| { |
| tree base = get_base_address (ref); |
| if (DECL_P (base)) |
| return base; |
| |
| if (TREE_CODE (base) == MEM_REF) |
| base = TREE_OPERAND (base, 0); |
| |
| if (TREE_CODE (base) != SSA_NAME) |
| return base; |
| |
| do |
| { |
| gimple *def = SSA_NAME_DEF_STMT (base); |
| if (gimple_assign_single_p (def)) |
| { |
| base = gimple_assign_rhs1 (def); |
| if (TREE_CODE (base) != ASSERT_EXPR) |
| return base; |
| |
| base = TREE_OPERAND (base, 0); |
| if (TREE_CODE (base) != SSA_NAME) |
| return base; |
| |
| continue; |
| } |
| |
| if (!gimple_nop_p (def)) |
| return base; |
| |
| break; |
| } while (true); |
| |
| tree var = SSA_NAME_VAR (base); |
| if (TREE_CODE (var) != PARM_DECL) |
| return base; |
| |
| return var; |
| } |
| |
| /* Return the constant byte size of the object or type referenced by |
| the MEM_REF ARG. On success, set *PREF to the DECL or expression |
| ARG refers to. Otherwise return null. */ |
| |
| static tree |
| get_ref_size (tree arg, tree *pref) |
| { |
| if (TREE_CODE (arg) != MEM_REF) |
| return NULL_TREE; |
| |
| arg = TREE_OPERAND (arg, 0); |
| tree type = TREE_TYPE (arg); |
| if (!POINTER_TYPE_P (type)) |
| return NULL_TREE; |
| |
| type = TREE_TYPE (type); |
| if (TREE_CODE (type) != ARRAY_TYPE) |
| return NULL_TREE; |
| |
| tree nbytes = TYPE_SIZE_UNIT (type); |
| if (!nbytes || TREE_CODE (nbytes) != INTEGER_CST) |
| return NULL_TREE; |
| |
| *pref = get_base_decl (arg); |
| return nbytes; |
| } |
| |
| /* Return true if REF is (likely) an ARRAY_REF to a trailing array member |
| of a struct. It refines array_at_struct_end_p by detecting a pointer |
| to an array and an array parameter declared using the [N] syntax (as |
| opposed to a pointer) and returning false. Set *PREF to the decl or |
| expression REF refers to. */ |
| |
| static bool |
| trailing_array (tree arg, tree *pref) |
| { |
| tree ref = arg; |
| tree base = get_base_decl (arg); |
| while (TREE_CODE (ref) == ARRAY_REF || TREE_CODE (ref) == MEM_REF) |
| ref = TREE_OPERAND (ref, 0); |
| |
| if (TREE_CODE (ref) == COMPONENT_REF) |
| { |
| *pref = TREE_OPERAND (ref, 1); |
| tree type = TREE_TYPE (*pref); |
| if (TREE_CODE (type) == ARRAY_TYPE) |
| { |
| /* A multidimensional trailing array is not considered special |
| no matter what its major bound is. */ |
| type = TREE_TYPE (type); |
| if (TREE_CODE (type) == ARRAY_TYPE) |
| return false; |
| } |
| } |
| else |
| *pref = base; |
| |
| tree basetype = TREE_TYPE (base); |
| if (TREE_CODE (base) == PARM_DECL |
| && POINTER_TYPE_P (basetype)) |
| { |
| tree ptype = TREE_TYPE (basetype); |
| if (TREE_CODE (ptype) == ARRAY_TYPE) |
| return false; |
| } |
| |
| return array_at_struct_end_p (arg); |
| } |
| |
| /* Checks one ARRAY_REF in REF, located at LOCUS. Ignores flexible |
| arrays and "struct" hacks. If VRP can determine that the array |
| subscript is a constant, check if it is outside valid range. If |
| the array subscript is a RANGE, warn if it is non-overlapping with |
| valid range. IGNORE_OFF_BY_ONE is true if the ARRAY_REF is inside |
| a ADDR_EXPR. Return true if a warning has been issued or if |
| no-warning is set. */ |
| |
| bool |
| array_bounds_checker::check_array_ref (location_t location, tree ref, |
| gimple *stmt, bool ignore_off_by_one) |
| { |
| if (warning_suppressed_p (ref, OPT_Warray_bounds)) |
| /* Return true to have the caller prevent warnings for enclosing |
| refs. */ |
| return true; |
| |
| tree low_sub = TREE_OPERAND (ref, 1); |
| tree up_sub = low_sub; |
| tree up_bound = array_ref_up_bound (ref); |
| |
| /* Referenced decl if one can be determined. */ |
| tree decl = NULL_TREE; |
| |
| /* Set for accesses to interior zero-length arrays. */ |
| special_array_member sam{ }; |
| |
| tree up_bound_p1; |
| |
| if (!up_bound |
| || TREE_CODE (up_bound) != INTEGER_CST |
| || (warn_array_bounds < 2 && trailing_array (ref, &decl))) |
| { |
| /* Accesses to trailing arrays via pointers may access storage |
| beyond the types array bounds. For such arrays, or for flexible |
| array members, as well as for other arrays of an unknown size, |
| replace the upper bound with a more permissive one that assumes |
| the size of the largest object is PTRDIFF_MAX. */ |
| tree eltsize = array_ref_element_size (ref); |
| |
| if (TREE_CODE (eltsize) != INTEGER_CST |
| || integer_zerop (eltsize)) |
| { |
| up_bound = NULL_TREE; |
| up_bound_p1 = NULL_TREE; |
| } |
| else |
| { |
| tree ptrdiff_max = TYPE_MAX_VALUE (ptrdiff_type_node); |
| tree maxbound = ptrdiff_max; |
| tree arg = TREE_OPERAND (ref, 0); |
| |
| const bool compref = TREE_CODE (arg) == COMPONENT_REF; |
| if (compref) |
| { |
| /* Try to determine the size of the trailing array from |
| its initializer (if it has one). */ |
| if (tree refsize = component_ref_size (arg, &sam)) |
| if (TREE_CODE (refsize) == INTEGER_CST) |
| maxbound = refsize; |
| } |
| |
| if (maxbound == ptrdiff_max) |
| { |
| /* Try to determine the size of the base object. Avoid |
| COMPONENT_REF already tried above. Using its DECL_SIZE |
| size wouldn't necessarily be correct if the reference is |
| to its flexible array member initialized in a different |
| translation unit. */ |
| poly_int64 off; |
| if (tree base = get_addr_base_and_unit_offset (arg, &off)) |
| { |
| if (TREE_CODE (base) == MEM_REF) |
| { |
| /* Try to determine the size from a pointer to |
| an array if BASE is one. */ |
| if (tree size = get_ref_size (base, &decl)) |
| maxbound = size; |
| } |
| else if (!compref && DECL_P (base)) |
| if (tree basesize = DECL_SIZE_UNIT (base)) |
| if (TREE_CODE (basesize) == INTEGER_CST) |
| { |
| maxbound = basesize; |
| decl = base; |
| } |
| |
| if (known_gt (off, 0)) |
| maxbound = wide_int_to_tree (sizetype, |
| wi::sub (wi::to_wide (maxbound), |
| off)); |
| } |
| } |
| else |
| maxbound = fold_convert (sizetype, maxbound); |
| |
| up_bound_p1 = int_const_binop (TRUNC_DIV_EXPR, maxbound, eltsize); |
| |
| if (up_bound_p1 != NULL_TREE) |
| up_bound = int_const_binop (MINUS_EXPR, up_bound_p1, |
| build_int_cst (ptrdiff_type_node, 1)); |
| else |
| up_bound = NULL_TREE; |
| } |
| } |
| else |
| up_bound_p1 = int_const_binop (PLUS_EXPR, up_bound, |
| build_int_cst (TREE_TYPE (up_bound), 1)); |
| |
| tree low_bound = array_ref_low_bound (ref); |
| |
| tree artype = TREE_TYPE (TREE_OPERAND (ref, 0)); |
| |
| bool warned = false; |
| |
| /* Empty array. */ |
| if (up_bound && tree_int_cst_equal (low_bound, up_bound_p1)) |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript %E is outside array bounds of %qT", |
| low_sub, artype); |
| |
| const value_range *vr = NULL; |
| if (TREE_CODE (low_sub) == SSA_NAME) |
| { |
| vr = get_value_range (low_sub, stmt); |
| if (!vr->undefined_p () && !vr->varying_p ()) |
| { |
| low_sub = vr->kind () == VR_RANGE ? vr->max () : vr->min (); |
| up_sub = vr->kind () == VR_RANGE ? vr->min () : vr->max (); |
| } |
| } |
| |
| if (warned) |
| ; /* Do nothing. */ |
| else if (vr && vr->kind () == VR_ANTI_RANGE) |
| { |
| if (up_bound |
| && TREE_CODE (up_sub) == INTEGER_CST |
| && (ignore_off_by_one |
| ? tree_int_cst_lt (up_bound, up_sub) |
| : tree_int_cst_le (up_bound, up_sub)) |
| && TREE_CODE (low_sub) == INTEGER_CST |
| && tree_int_cst_le (low_sub, low_bound)) |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript [%E, %E] is outside " |
| "array bounds of %qT", |
| low_sub, up_sub, artype); |
| } |
| else if (up_bound |
| && TREE_CODE (up_sub) == INTEGER_CST |
| && (ignore_off_by_one |
| ? !tree_int_cst_le (up_sub, up_bound_p1) |
| : !tree_int_cst_le (up_sub, up_bound))) |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript %E is above array bounds of %qT", |
| up_sub, artype); |
| else if (TREE_CODE (low_sub) == INTEGER_CST |
| && tree_int_cst_lt (low_sub, low_bound)) |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript %E is below array bounds of %qT", |
| low_sub, artype); |
| |
| if (!warned && sam == special_array_member::int_0) |
| warned = warning_at (location, OPT_Wzero_length_bounds, |
| (TREE_CODE (low_sub) == INTEGER_CST |
| ? G_("array subscript %E is outside the bounds " |
| "of an interior zero-length array %qT") |
| : G_("array subscript %qE is outside the bounds " |
| "of an interior zero-length array %qT")), |
| low_sub, artype); |
| |
| if (warned) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "Array bound warning for "); |
| dump_generic_expr (MSG_NOTE, TDF_SLIM, ref); |
| fprintf (dump_file, "\n"); |
| } |
| |
| /* Avoid more warnings when checking more significant subscripts |
| of the same expression. */ |
| ref = TREE_OPERAND (ref, 0); |
| suppress_warning (ref, OPT_Warray_bounds); |
| |
| if (decl) |
| ref = decl; |
| |
| tree rec = NULL_TREE; |
| if (TREE_CODE (ref) == COMPONENT_REF) |
| { |
| /* For a reference to a member of a struct object also mention |
| the object if it's known. It may be defined in a different |
| function than the out-of-bounds access. */ |
| rec = TREE_OPERAND (ref, 0); |
| if (!VAR_P (rec)) |
| rec = NULL_TREE; |
| ref = TREE_OPERAND (ref, 1); |
| } |
| |
| if (DECL_P (ref)) |
| inform (DECL_SOURCE_LOCATION (ref), "while referencing %qD", ref); |
| if (rec && DECL_P (rec)) |
| inform (DECL_SOURCE_LOCATION (rec), "defined here %qD", rec); |
| } |
| |
| return warned; |
| } |
| |
| /* Wrapper around build_array_type_nelts that makes sure the array |
| can be created at all and handles zero sized arrays specially. */ |
| |
| static tree |
| build_printable_array_type (tree eltype, unsigned HOST_WIDE_INT nelts) |
| { |
| if (TYPE_SIZE_UNIT (eltype) |
| && TREE_CODE (TYPE_SIZE_UNIT (eltype)) == INTEGER_CST |
| && !integer_zerop (TYPE_SIZE_UNIT (eltype)) |
| && TYPE_ALIGN_UNIT (eltype) > 1 |
| && wi::zext (wi::to_wide (TYPE_SIZE_UNIT (eltype)), |
| ffs_hwi (TYPE_ALIGN_UNIT (eltype)) - 1) != 0) |
| eltype = TYPE_MAIN_VARIANT (eltype); |
| |
| if (nelts) |
| return build_array_type_nelts (eltype, nelts); |
| |
| tree idxtype = build_range_type (sizetype, size_zero_node, NULL_TREE); |
| tree arrtype = build_array_type (eltype, idxtype); |
| arrtype = build_distinct_type_copy (TYPE_MAIN_VARIANT (arrtype)); |
| TYPE_SIZE (arrtype) = bitsize_zero_node; |
| TYPE_SIZE_UNIT (arrtype) = size_zero_node; |
| return arrtype; |
| } |
| |
| /* Checks one MEM_REF in REF, located at LOCATION, for out-of-bounds |
| references to string constants. If VRP can determine that the array |
| subscript is a constant, check if it is outside valid range. |
| If the array subscript is a RANGE, warn if it is non-overlapping |
| with valid range. |
| IGNORE_OFF_BY_ONE is true if the MEM_REF is inside an ADDR_EXPR |
| (used to allow one-past-the-end indices for code that takes |
| the address of the just-past-the-end element of an array). |
| Returns true if a warning has been issued. */ |
| |
| bool |
| array_bounds_checker::check_mem_ref (location_t location, tree ref, |
| bool ignore_off_by_one) |
| { |
| if (warning_suppressed_p (ref, OPT_Warray_bounds)) |
| return false; |
| |
| /* The statement used to allocate the array or null. */ |
| gimple *alloc_stmt = NULL; |
| /* For an allocation statement, the low bound of the size range. */ |
| offset_int minbound = 0; |
| /* The type and size of the access. */ |
| tree axstype = TREE_TYPE (ref); |
| offset_int axssize = 0; |
| if (tree access_size = TYPE_SIZE_UNIT (axstype)) |
| if (TREE_CODE (access_size) == INTEGER_CST) |
| axssize = wi::to_offset (access_size); |
| |
| access_ref aref; |
| if (!compute_objsize (ref, m_stmt, 0, &aref, ranges)) |
| return false; |
| |
| if (aref.offset_in_range (axssize)) |
| return false; |
| |
| if (TREE_CODE (aref.ref) == SSA_NAME) |
| { |
| gimple *def = SSA_NAME_DEF_STMT (aref.ref); |
| if (is_gimple_call (def)) |
| { |
| /* Save the allocation call and the low bound on the size. */ |
| alloc_stmt = def; |
| minbound = aref.sizrng[0]; |
| } |
| } |
| |
| /* The range of the byte offset into the reference. Adjusted below. */ |
| offset_int offrange[2] = { aref.offrng[0], aref.offrng[1] }; |
| |
| /* The type of the referenced object. */ |
| tree reftype = TREE_TYPE (aref.ref); |
| /* The size of the referenced array element. */ |
| offset_int eltsize = 1; |
| if (POINTER_TYPE_P (reftype)) |
| reftype = TREE_TYPE (reftype); |
| |
| if (TREE_CODE (reftype) == FUNCTION_TYPE) |
| /* Restore the original (pointer) type and avoid trying to create |
| an array of functions (done below). */ |
| reftype = TREE_TYPE (aref.ref); |
| else |
| { |
| /* The byte size of the array has already been determined above |
| based on a pointer ARG. Set ELTSIZE to the size of the type |
| it points to and REFTYPE to the array with the size, rounded |
| down as necessary. */ |
| if (TREE_CODE (reftype) == ARRAY_TYPE) |
| reftype = TREE_TYPE (reftype); |
| if (tree refsize = TYPE_SIZE_UNIT (reftype)) |
| if (TREE_CODE (refsize) == INTEGER_CST) |
| eltsize = wi::to_offset (refsize); |
| |
| const offset_int nelts = aref.sizrng[1] / eltsize; |
| reftype = build_printable_array_type (reftype, nelts.to_uhwi ()); |
| } |
| |
| /* Compute the more permissive upper bound when IGNORE_OFF_BY_ONE |
| is set (when taking the address of the one-past-last element |
| of an array) but always use the stricter bound in diagnostics. */ |
| offset_int ubound = aref.sizrng[1]; |
| if (ignore_off_by_one) |
| ubound += eltsize; |
| |
| /* Set if the lower bound of the subscript is out of bounds. */ |
| const bool lboob = (aref.sizrng[1] == 0 |
| || offrange[0] >= ubound |
| || offrange[1] < 0); |
| /* Set if only the upper bound of the subscript is out of bounds. |
| This can happen when using a bigger type to index into an array |
| of a smaller type, as is common with unsigned char. */ |
| const bool uboob = !lboob && offrange[0] + axssize > ubound; |
| if (lboob || uboob) |
| { |
| /* Treat a reference to a non-array object as one to an array |
| of a single element. */ |
| if (TREE_CODE (reftype) != ARRAY_TYPE) |
| reftype = build_printable_array_type (reftype, 1); |
| |
| /* Extract the element type out of MEM_REF and use its size |
| to compute the index to print in the diagnostic; arrays |
| in MEM_REF don't mean anything. A type with no size like |
| void is as good as having a size of 1. */ |
| tree type = strip_array_types (TREE_TYPE (ref)); |
| if (tree size = TYPE_SIZE_UNIT (type)) |
| { |
| offrange[0] = offrange[0] / wi::to_offset (size); |
| offrange[1] = offrange[1] / wi::to_offset (size); |
| } |
| } |
| |
| bool warned = false; |
| if (lboob) |
| { |
| if (offrange[0] == offrange[1]) |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript %wi is outside array bounds " |
| "of %qT", |
| offrange[0].to_shwi (), reftype); |
| else |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript [%wi, %wi] is outside " |
| "array bounds of %qT", |
| offrange[0].to_shwi (), |
| offrange[1].to_shwi (), reftype); |
| } |
| else if (uboob && !ignore_off_by_one) |
| { |
| tree backtype = reftype; |
| if (alloc_stmt) |
| /* If the memory was dynamically allocated refer to it as if |
| it were an untyped array of bytes. */ |
| backtype = build_array_type_nelts (unsigned_char_type_node, |
| aref.sizrng[1].to_uhwi ()); |
| |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript %<%T[%wi]%> is partly " |
| "outside array bounds of %qT", |
| axstype, offrange[0].to_shwi (), backtype); |
| } |
| |
| if (warned) |
| { |
| /* TODO: Determine the access from the statement and use it. */ |
| aref.inform_access (access_none); |
| suppress_warning (ref, OPT_Warray_bounds); |
| return true; |
| } |
| |
| if (warn_array_bounds < 2) |
| return false; |
| |
| /* At level 2 check also intermediate offsets. */ |
| int i = 0; |
| if (aref.offmax[i] < -aref.sizrng[1] || aref.offmax[i = 1] > ubound) |
| { |
| HOST_WIDE_INT tmpidx = aref.offmax[i].to_shwi () / eltsize.to_shwi (); |
| |
| if (warning_at (location, OPT_Warray_bounds, |
| "intermediate array offset %wi is outside array bounds " |
| "of %qT", tmpidx, reftype)) |
| { |
| suppress_warning (ref, OPT_Warray_bounds); |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /* Searches if the expr T, located at LOCATION computes |
| address of an ARRAY_REF, and call check_array_ref on it. */ |
| |
| void |
| array_bounds_checker::check_addr_expr (location_t location, tree t, |
| gimple *stmt) |
| { |
| /* For the most significant subscript only, accept taking the address |
| of the just-past-the-end element. */ |
| bool ignore_off_by_one = true; |
| |
| /* Check each ARRAY_REF and MEM_REF in the reference chain. */ |
| do |
| { |
| bool warned = false; |
| if (TREE_CODE (t) == ARRAY_REF) |
| { |
| warned = check_array_ref (location, t, stmt, ignore_off_by_one); |
| ignore_off_by_one = false; |
| } |
| else if (TREE_CODE (t) == MEM_REF) |
| warned = check_mem_ref (location, t, ignore_off_by_one); |
| |
| if (warned) |
| suppress_warning (t, OPT_Warray_bounds); |
| |
| t = TREE_OPERAND (t, 0); |
| } |
| while (handled_component_p (t) || TREE_CODE (t) == MEM_REF); |
| |
| if (TREE_CODE (t) != MEM_REF |
| || TREE_CODE (TREE_OPERAND (t, 0)) != ADDR_EXPR |
| || warning_suppressed_p (t, OPT_Warray_bounds)) |
| return; |
| |
| tree tem = TREE_OPERAND (TREE_OPERAND (t, 0), 0); |
| tree low_bound, up_bound, el_sz; |
| if (TREE_CODE (TREE_TYPE (tem)) != ARRAY_TYPE |
| || TREE_CODE (TREE_TYPE (TREE_TYPE (tem))) == ARRAY_TYPE |
| || !TYPE_DOMAIN (TREE_TYPE (tem))) |
| return; |
| |
| low_bound = TYPE_MIN_VALUE (TYPE_DOMAIN (TREE_TYPE (tem))); |
| up_bound = TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (tem))); |
| el_sz = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (tem))); |
| if (!low_bound |
| || TREE_CODE (low_bound) != INTEGER_CST |
| || !up_bound |
| || TREE_CODE (up_bound) != INTEGER_CST |
| || !el_sz |
| || TREE_CODE (el_sz) != INTEGER_CST) |
| return; |
| |
| offset_int idx; |
| if (!mem_ref_offset (t).is_constant (&idx)) |
| return; |
| |
| bool warned = false; |
| idx = wi::sdiv_trunc (idx, wi::to_offset (el_sz)); |
| if (idx < 0) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "Array bound warning for "); |
| dump_generic_expr (MSG_NOTE, TDF_SLIM, t); |
| fprintf (dump_file, "\n"); |
| } |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript %wi is below " |
| "array bounds of %qT", |
| idx.to_shwi (), TREE_TYPE (tem)); |
| } |
| else if (idx > (wi::to_offset (up_bound) |
| - wi::to_offset (low_bound) + 1)) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "Array bound warning for "); |
| dump_generic_expr (MSG_NOTE, TDF_SLIM, t); |
| fprintf (dump_file, "\n"); |
| } |
| warned = warning_at (location, OPT_Warray_bounds, |
| "array subscript %wu is above " |
| "array bounds of %qT", |
| idx.to_uhwi (), TREE_TYPE (tem)); |
| } |
| |
| if (warned) |
| { |
| if (DECL_P (t)) |
| inform (DECL_SOURCE_LOCATION (t), "while referencing %qD", t); |
| |
| suppress_warning (t, OPT_Warray_bounds); |
| } |
| } |
| |
| /* Return true if T is a reference to a member of a base class that's within |
| the bounds of the enclosing complete object. The function "hacks" around |
| problems discussed in pr98266 and pr97595. */ |
| |
| static bool |
| inbounds_memaccess_p (tree t, gimple *stmt) |
| { |
| if (TREE_CODE (t) != COMPONENT_REF) |
| return false; |
| |
| tree mref = TREE_OPERAND (t, 0); |
| if (TREE_CODE (mref) != MEM_REF) |
| return false; |
| |
| /* Consider the access if its type is a derived class. */ |
| tree mreftype = TREE_TYPE (mref); |
| if (!RECORD_OR_UNION_TYPE_P (mreftype) |
| || !TYPE_BINFO (mreftype)) |
| return false; |
| |
| /* Compute the size of the referenced object (it could be dynamically |
| allocated). */ |
| access_ref aref; // unused |
| tree refop = TREE_OPERAND (mref, 0); |
| tree refsize = compute_objsize (refop, stmt, 1, &aref); |
| if (!refsize || TREE_CODE (refsize) != INTEGER_CST) |
| return false; |
| |
| /* Compute the byte offset of the member within its enclosing class. */ |
| tree fld = TREE_OPERAND (t, 1); |
| tree fldpos = byte_position (fld); |
| if (TREE_CODE (fldpos) != INTEGER_CST) |
| return false; |
| |
| /* Compute the byte offset of the member with the outermost complete |
| object by adding its offset computed above to the MEM_REF offset. */ |
| tree refoff = TREE_OPERAND (mref, 1); |
| tree fldoff = int_const_binop (PLUS_EXPR, fldpos, refoff); |
| /* Return false if the member offset is greater or equal to the size |
| of the complete object. */ |
| if (!tree_int_cst_lt (fldoff, refsize)) |
| return false; |
| |
| tree fldsiz = DECL_SIZE_UNIT (fld); |
| if (!fldsiz || TREE_CODE (fldsiz) != INTEGER_CST) |
| return false; |
| |
| /* Return true if the offset just past the end of the member is less |
| than or equal to the size of the complete object. */ |
| tree fldend = int_const_binop (PLUS_EXPR, fldoff, fldsiz); |
| return tree_int_cst_le (fldend, refsize); |
| } |
| |
| /* Callback for walk_tree to check a tree for out of bounds array |
| accesses. The array_bounds_checker class is passed in DATA. */ |
| |
| tree |
| array_bounds_checker::check_array_bounds (tree *tp, int *walk_subtree, |
| void *data) |
| { |
| tree t = *tp; |
| struct walk_stmt_info *wi = (struct walk_stmt_info *) data; |
| |
| location_t location; |
| |
| if (EXPR_HAS_LOCATION (t)) |
| location = EXPR_LOCATION (t); |
| else |
| location = gimple_location (wi->stmt); |
| |
| *walk_subtree = TRUE; |
| |
| bool warned = false; |
| array_bounds_checker *checker = (array_bounds_checker *) wi->info; |
| gcc_assert (checker->m_stmt == wi->stmt); |
| |
| if (TREE_CODE (t) == ARRAY_REF) |
| warned = checker->check_array_ref (location, t, wi->stmt, |
| false/*ignore_off_by_one*/); |
| else if (TREE_CODE (t) == MEM_REF) |
| warned = checker->check_mem_ref (location, t, |
| false /*ignore_off_by_one*/); |
| else if (TREE_CODE (t) == ADDR_EXPR) |
| { |
| checker->check_addr_expr (location, t, wi->stmt); |
| *walk_subtree = false; |
| } |
| else if (inbounds_memaccess_p (t, wi->stmt)) |
| /* Hack: Skip MEM_REF checks in accesses to a member of a base class |
| at an offset that's within the bounds of the enclosing object. |
| See pr98266 and pr97595. */ |
| *walk_subtree = false; |
| |
| /* Propagate the no-warning bit to the outer statement to avoid also |
| issuing -Wstringop-overflow/-overread for the out-of-bounds accesses. */ |
| if (warned) |
| suppress_warning (wi->stmt, OPT_Warray_bounds); |
| |
| return NULL_TREE; |
| } |
| |
| /* A dom_walker subclass for use by check_all_array_refs, to walk over |
| all statements of all reachable BBs and call check_array_bounds on |
| them. */ |
| |
| class check_array_bounds_dom_walker : public dom_walker |
| { |
| public: |
| check_array_bounds_dom_walker (array_bounds_checker *checker) |
| : dom_walker (CDI_DOMINATORS, |
| /* Discover non-executable edges, preserving EDGE_EXECUTABLE |
| flags, so that we can merge in information on |
| non-executable edges from vrp_folder . */ |
| REACHABLE_BLOCKS_PRESERVING_FLAGS), |
| checker (checker) { } |
| ~check_array_bounds_dom_walker () {} |
| |
| edge before_dom_children (basic_block) FINAL OVERRIDE; |
| |
| private: |
| array_bounds_checker *checker; |
| }; |
| |
| /* Implementation of dom_walker::before_dom_children. |
| |
| Walk over all statements of BB and call check_array_bounds on them, |
| and determine if there's a unique successor edge. */ |
| |
| edge |
| check_array_bounds_dom_walker::before_dom_children (basic_block bb) |
| { |
| gimple_stmt_iterator si; |
| for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si)) |
| { |
| gimple *stmt = gsi_stmt (si); |
| if (!gimple_has_location (stmt) |
| || is_gimple_debug (stmt)) |
| continue; |
| |
| struct walk_stmt_info wi{ }; |
| wi.info = checker; |
| checker->m_stmt = stmt; |
| |
| walk_gimple_op (stmt, array_bounds_checker::check_array_bounds, &wi); |
| } |
| |
| /* Determine if there's a unique successor edge, and if so, return |
| that back to dom_walker, ensuring that we don't visit blocks that |
| became unreachable during the VRP propagation |
| (PR tree-optimization/83312). */ |
| return find_taken_edge (bb, NULL_TREE); |
| } |
| |
| void |
| array_bounds_checker::check () |
| { |
| check_array_bounds_dom_walker w (this); |
| w.walk (ENTRY_BLOCK_PTR_FOR_FN (fun)); |
| } |