https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94355
--- Comment #16 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Benjamin Priour <vultk...@gcc.gnu.org>: https://gcc.gnu.org/g:e7b267444045c507654a2a3f758efee5d5b550df commit r14-3632-ge7b267444045c507654a2a3f758efee5d5b550df Author: benjamin priour <priour...@gmail.com> Date: Fri Sep 1 00:01:29 2023 +0200 analyzer: Add support of placement new and improved operator new [PR105948,PR94355] Fixed spurious possibly-NULL warning always tagging along throwing operator new despite it never returning NULL. Now operator new is correctly recognized as possibly returning NULL if and only if it is non-throwing or exceptions have been disabled. Different standard signatures of operator new are now properly recognized. Added support of placement new, so that it is now properly recognized, and a 'heap_allocated' region is no longer created for it. Placement new size is also checked and a 'Wanalyzer-allocation-size' is emitted when relevant, as well as always a 'Wanalyzer-out-of-bounds'. 'operator new' non-throwing variants are detected y checking the types of the parameters. Indeed, in a call to new (std::nothrow) () the chosen overload has signature 'operator new (void*, std::nothrow_t&)', where the second parameter is a reference. In a placement new, the second parameter will always be a void pointer. Prior to this patch, some buffers first allocated with 'new', then deleted an thereafter used would result in a 'Wanalyzer-user-after-free' warning. However the wording was "use after 'free'" instead of the expected "use after 'delete'". This patch fixes this by introducing a new kind of poisoned value, namely POISON_KIND_DELETED. Due to how the analyzer sees calls to non-throwing variants of operator new, dereferencing a pointer freshly allocated in this fashion caused both a 'Wanalyzer-use-of-uninitialized-value' and a 'Wanalyzer-null-dereference' to be emitted, while only the latter was relevant. As a result, 'null-dereference' now supersedes 'use-of-uninitialized'. Signed-off-by: benjamin priour <vultk...@gcc.gnu.org> gcc/analyzer/ChangeLog: PR analyzer/105948 PR analyzer/94355 * analyzer.h (is_placement_new_p): New declaration. * call-details.cc (call_details::deref_ptr_arg): New function. Dereference the argument at given index if possible. * call-details.h: Declaration of the above function. * kf-lang-cp.cc (is_placement_new_p): Returns true if the gcall is recognized as a placement new. (kf_operator_delete::impl_call_post): Unbinding a region and its descendents now poisons with POISON_KIND_DELETED. (register_known_functions_lang_cp): Known function "operator delete" is now registered only once independently of its number of arguments. * region-model.cc (region_model::eval_condition): Now recursively calls itself if any of the operand is wrapped in a cast. * sm-malloc.cc (malloc_state_machine::on_stmt): Add placement new recognition. * svalue.cc (poison_kind_to_str): Wording for the new PK. * svalue.h (enum poison_kind): Add value POISON_KIND_DELETED. gcc/testsuite/ChangeLog: PR analyzer/105948 PR analyzer/94355 * g++.dg/analyzer/out-of-bounds-placement-new.C: Added a directive. * g++.dg/analyzer/placement-new.C: Added tests. * g++.dg/analyzer/new-2.C: New test. * g++.dg/analyzer/noexcept-new.C: New test. * g++.dg/analyzer/placement-new-size.C: New test.
