[Bug analyzer/94378] -Wanalyzer-malloc-leak false positive when returning a struct by value holding a heap-allocated pointer

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94378

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:a96f1c38a787fbc847cb014d4b094e2787d539a7

commit r10-7502-ga96f1c38a787fbc847cb014d4b094e2787d539a7
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Mon Mar 30 17:02:59 2020 -0400

    analyzer: handle compound assignments [PR94378]

    PR analyzer/94378 reports a false -Wanalyzer-malloc-leak
    when returning a struct containing a malloc-ed pointer.

    The issue is that the assignment code was not handling
    compound copies, only copying top-level values from region to region,
    and not copying child values.

    This patch introduces a region_model::copy_region function, using
    it for assignments and when analyzing function return values.
    It recursively copies nested values within structs, unions, and
    arrays, fixing the bug.

    gcc/analyzer/ChangeLog:
            PR analyzer/94378
            * checker-path.cc: Include "bitmap.h".
            * constraint-manager.cc: Likewise.
            * diagnostic-manager.cc: Likewise.
            * engine.cc: Likewise.
            (exploded_node::detect_leaks): Pass null region_id to pop_frame.
            * program-point.cc: Include "bitmap.h".
            * program-state.cc: Likewise.
            * region-model.cc (id_set<region_id>::id_set): Convert to...
            (region_id_set::region_id_set): ...this.
            (svalue_id_set::svalue_id_set): New ctor.
            (region_model::copy_region): New function.
            (region_model::copy_struct_region): New function.
            (region_model::copy_union_region): New function.
            (region_model::copy_array_region): New function.
            (stack_region::pop_frame): Drop return value.  Add
            "result_dst_rid" param; if it is non-null, use copy_region to copy
            the result to it.  Rather than capture and pass a single "known
            used" return value to be used by purge_unused_values, instead
            gather and pass a set of known used return values.
            (root_region::pop_frame): Drop return value.  Add "result_dst_rid"
            param.
            (region_model::on_assignment): Use copy_region.
            (region_model::on_return): Likewise for the result.
            (region_model::on_longjmp): Pass null for pop_frame's
            result_dst_rid.
            (region_model::update_for_return_superedge): Pass the region for
the
            return value of the call, if any, to pop_frame, rather than setting
            the lvalue for the lhs of the result.
            (region_model::pop_frame): Drop return value.  Add
            "result_dst_rid" param.
            (region_model::purge_unused_svalues): Convert third param from an
            svalue_id * to an svalue_id_set *, updating the initial populating
            of the "used" bitmap accordingly.  Don't remap it when done.
            (struct selftest::coord_test): New selftest fixture, extracted
from...
            (selftest::test_dump_2): ...here.
            (selftest::test_compound_assignment): New selftest.
            (selftest::test_stack_frames): Pass null to new param of pop_frame.
            (selftest::analyzer_region_model_cc_tests): Call the new selftest.
            * region-model.h (class id_set): Delete template.
            (class region_id_set): Reimplement, using old id_set
implementation.
            (class svalue_id_set): Likewise.  Convert from auto_sbitmap to
            auto_bitmap.
            (region::get_active_view): New accessor.
            (stack_region::pop_frame): Drop return value.  Add
            "result_dst_rid" param.
            (root_region::pop_frame): Likewise.
            (region_model::pop_frame): Likewise.
            (region_model::copy_region): New decl.
            (region_model::purge_unused_svalues): Convert third param from an
            svalue_id * to an svalue_id_set *.
            (region_model::copy_struct_region): New decl.
            (region_model::copy_union_region): New decl.
            (region_model::copy_array_region): New decl.

    gcc/testsuite/ChangeLog:
            PR analyzer/94378
            * gcc.dg/analyzer/compound-assignment-1.c: New test.
            * gcc.dg/analyzer/compound-assignment-2.c: New test.
            * gcc.dg/analyzer/compound-assignment-3.c: New test.