analyzer: add allocation size checker [PR105900]

This patch adds an checker that warns about code paths in which a buffer
is assigned to a incompatible type, i.e. when the allocated buffer size
is not a multiple of the pointee's size.

Regression-tested on x86_64 Linux. Also compiled coreutils, curl, openssh and
httpd with the patch enabled.

2022-07-01  Tim Lange  <mail@tim-lange.me>

gcc/analyzer/ChangeLog:

	PR analyzer/105900
	* analyzer.opt: Added Wanalyzer-allocation-size.
	* checker-path.cc (region_creation_event::get_desc): Added call to new
	virtual function pending_diagnostic::describe_region_creation_event.
	* checker-path.h: Added region_creation_event::get_desc.
	* diagnostic-manager.cc (diagnostic_manager::add_event_on_final_node):
	New function.
	* diagnostic-manager.h:
	Added diagnostic_manager::add_event_on_final_node.
	* pending-diagnostic.h (struct region_creation): New event_desc struct.
	(pending_diagnostic::describe_region_creation_event): Added virtual
	function to overwrite description of a region creation.
	* region-model.cc (class dubious_allocation_size): New class.
	(capacity_compatible_with_type): New helper function.
	(class size_visitor): New class.
	(struct_or_union_with_inheritance_p): New helper function.
	(is_any_cast_p): New helper function.
	(region_model::check_region_size): New function.
	(region_model::set_value): Added call to
	region_model::check_region_size.
	* region-model.h (class region_model): New function check_region_size.
	* svalue.cc (region_svalue::accept): Changed to post-order traversal.
	(initial_svalue::accept): Likewise.
	(unaryop_svalue::accept): Likewise.
	(binop_svalue::accept): Likewise.
	(sub_svalue::accept): Likewise.
	(repeated_svalue::accept): Likewise.
	(bits_within_svalue::accept): Likewise.
	(widening_svalue::accept): Likewise.
	(unmergeable_svalue::accept): Likewise.
	(compound_svalue::accept): Likewise.
	(conjured_svalue::accept): Likewise.
	(asm_output_svalue::accept): Likewise.
	(const_fn_result_svalue::accept): Likewise.

gcc/ChangeLog:

	PR analyzer/105900
	* doc/invoke.texi: Added Wanalyzer-allocation-size.

gcc/testsuite/ChangeLog:

	PR analyzer/105900
	* gcc.dg/analyzer/pr96639.c: Changed buffer size to omit warning.
	* gcc.dg/analyzer/allocation-size-1.c: New test.
	* gcc.dg/analyzer/allocation-size-2.c: New test.
	* gcc.dg/analyzer/allocation-size-3.c: New test.
	* gcc.dg/analyzer/allocation-size-4.c: New test.
	* gcc.dg/analyzer/allocation-size-5.c: New test.

Signed-off-by: Tim Lange <mail@tim-lange.me>