analyzer: fix ICEs due to sloppy types in bounds-checking [PR110902,PR110928,PR111305,PR111441]
Various analyzer ICEs in our bugzilla relate to sloppy use of types
within bounds-checking.
The bounds-checking code works by comparing symbolic *bit* offsets, and
we don't have a good user-facing type that can represent such an offset
(ptrdiff_type_node is for *byte* offsets).
ana::svalue doesn't enforce valid combinations of types for things like
binary operations. When I added the access diagrams for GCC 14, this
could lead to attempts to generate trees for such svalues, leading to
trees with invalid combinations of types (e.g. PLUS_EXPR or MULT_EXPR of
incompatible types), leading to ICEs inside the tree folding logic.
I tried two approaches to fixing this.
My first approach was to fix the type-handling throughout the
bounds-checking code to use correct types, using size_type_node for
sizes, ptrdiff_type_node for byte offsets, and trying ptrdiff_type_node
for bit offsets. I implemented this, and it fixed the crashes, but
unfortunately it led to:
(a) numerous false negatives from the bounds-checking code, due to it
becoming unable to be sure that the accessed offset was beyond the valid
bounds, due to the expressions involved gaining complicated sets of
nested casts.
(b) ugly access diagrams full of nested casts (for capacities, gap
measurements, etc)
So my second approach, implemented in this patch, is to accept that we
don't have a tree type for representing bit offsets. The patch
represents bit offsets using "typeless" symbolic values i.e. ones for
which get_type () is NULL_TREE, and implements enough support for basic
arithemetic as if these are mathematical integers (albeit ones for which
concrete values within an expression must fit within a signed wide int).
Such values can't be converted to tree, so the patch avoids such
conversions, instead implementing a new svalue::maybe_print_for_user for
printing them to a pretty_printer. The patch uses ptrdiff_type_node for
byte offsets.
Doing so fixes the crashes, whilst appearing to preserve the behavior of
-Wanalyzer-out-of-bounds in my testing.
gcc/analyzer/ChangeLog:
PR analyzer/110902
PR analyzer/110928
PR analyzer/111305
PR analyzer/111441
* access-diagram.cc: Include "analyzer/analyzer-selftests.h".
(get_access_size_str): Reimplement for conversion of
implmementation of bit_size_expr from tree to const svalue &. Use
svalue::maybe_print_for_user rather than tree printing routines.
(remove_ssa_names): Make non-static.
(bit_size_expr::get_formatted_str): Rename to...
(bit_size_expr::maybe_get_formatted_str): ...this, adding "model"
param and converting return type to a unique_ptr. Update for
conversion of implementation of bit_size_expr from tree to
const svalue &. Use svalue::maybe_print_for_user rather than tree
printing routines.
(bit_size_expr::print): Rename to...
(bit_size_expr::maybe_print_for_user): ...this, adding "model"
param and converting return type to bool. Update for
conversion of implementation of bit_size_expr from tree to
const svalue &. Use svalue::maybe_print_for_user rather than tree
printing routines.
(bit_size_expr::maybe_get_as_bytes): Add "mgr" param and convert
return type from tree to const svalue *; reimplement.
(access_range::access_range): Call strip_types when on region_offset
intializations.
(access_range::get_size): Update for conversion of implementation
of bit_size_expr from tree to const svalue &.
(access_operation::get_valid_bits): Pass manager to access_range
ctor.
(access_operation::maybe_get_invalid_before_bits): Likewise.
(access_operation::maybe_get_invalid_after_bits): Likewise.
(boundaries::add): Likewise.
(bit_to_table_map::populate): Add "mgr" param and pass it to
access_range ctor.
(access_diagram_impl::access_diagram_impl): Pass manager to
bit_to_table_map::populate.
(access_diagram_impl::maybe_add_gap): Use svalue rather than tree
for symbolic bit offsets. Port to new bit_size_expr
representation.
(access_diagram_impl::add_valid_vs_invalid_ruler): Port to new
bit_size_expr representation.
(selftest::assert_eq_typeless_integer): New.
(ASSERT_EQ_TYPELESS_INTEGER): New.
(selftest::test_bit_size_expr_to_bytes): New.
(selftest::analyzer_access_diagram_cc_tests): New.
* access-diagram.h (class bit_size_expr): Reimplement, converting
implementation from tree to const svalue &.
(access_range::access_range): Add "mgr" param. Call strip_types
on region_offset initializations.
(access_range::get_size): Update decl for reimplementation.
* analyzer-selftests.cc (selftest::run_analyzer_selftests): Call
selftest::analyzer_access_diagram_cc_tests.
* analyzer-selftests.h
(selftest::analyzer_checker_script_cc_tests): Delete this stray
typo.
(selftest::analyzer_access_diagram_cc_tests): New decl.
* analyzer.h (print_expr_for_user): New decl.
(calc_symbolic_bit_offset): Update decl for reimplementation.
(strip_types): New decls.
(remove_ssa_names): New decl.
* bounds-checking.cc (strip_types): New.
(region_model::check_symbolic_bounds): Use typeless svalues.
* region-model-manager.cc
(region_model_manager::get_or_create_constant_svalue): Add "type"
param. Add overload with old signature.
(region_model_manager::get_or_create_int_cst): Support type being
NULL_TREE.
(region_model_manager::maybe_fold_unaryop): Gracefully reject folding
of casts to NULL_TREE type.
(get_code_for_cast): Use NOP_EXPR for "casting" svalues to
NULL_TREE type.
(region_model_manager::get_or_create_cast): Support "casting"
svalues to NULL_TREE type.
(region_model_manager::maybe_fold_binop): Don't crash on inputs
with NULL_TREE type. Handle folding of binops on constants with
NULL_TREE type. Add missing cast from PR analyzer/110902.
Support enough folding of other ops on NULL_TREE type to support
bounds checking.
(region_model_manager::get_or_create_const_fn_result_svalue):
Remove assertion that type is nonnull.
* region-model-manager.h
(region_model_manager::get_or_create_constant_svalue): Add
overloaded decl taking a type.
(region_model_manager::maybe_fold_binop): Make public.
(region_model_manager::constants_map_t): Use
constant_svalue::key_t for the key, rather than just tree.
* region-model.cc (print_expr_for_user): New.
(selftest::test_array_2): Handle casts.
* region.cc (region_offset::calc_symbolic_bit_offset): Return
const svalue & rather than tree, and reimplement accordingly.
(region::calc_offset): Use ptrdiff_type_node for types of byte
offsets.
(region::maybe_print_for_user): New.
(element_region::get_relative_symbolic_offset): Use NULL_TREE for
types of bit offsets.
(offset_region::get_bit_offset): Likewise.
(sized_region::get_bit_size_sval): Likewise for bit sizes.
* region.h (region::maybe_print_for_user): New decl.
* svalue.cc (class auto_add_parens): New.
(svalue::maybe_print_for_user): New.
(svalue::cmp_ptr): Support typeless constant svalues.
(tristate_from_boolean_tree_node): New, taken from...
(constant_svalue::eval_condition): ...here. Handle comparison of
typeless integer svalue constants.
* svalue.h (svalue::maybe_print_for_user): New decl.
(class constant_svalue): Support the type of the svalue being
NULL_TREE.
(struct default_hash_traits<constant_svalue::key_t>): New.
git://gcc.gnu.org / gcc.git / commit