https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77425
--- Comment #7 from CVS Commits ---
The master branch has been updated by David Malcolm :
https://gcc.gnu.org/g:5c6546ca7d8cab1f1c129f5b55f709e2ceee0f94
commit r13-3884-g5c6546ca7d8cab1f1c129f5b55f709e2ceee0f94
Author: David Malcolm
Date: Thu Nov 10 13:23:56 2022 -0500
analyzer: new warning: -Wanalyzer-deref-before-check [PR99671]
This patch implements a new -Wanalyzer-deref-before-check within
-fanalyzer. It complains about code paths in which a pointer is checked
for NULL after it has already been dereferenced.
For example, for the testcase in PR 77432 the diagnostic emits:
deref-before-check-1.c: In function 'test_from_pr77432':
deref-before-check-1.c:6:8: warning: check of 'a' for NULL after already
dereferencing it [-Wanalyzer-deref-before-check]
6 | if (a)
|^
'test_from_pr77432': events 1-2
|
|5 | int b = *a;
| | ^
| | |
| | (1) pointer 'a' is dereferenced here
|6 | if (a)
| |~
| ||
| |(2) pointer 'a' is checked for NULL here but it was
already dereferenced at (1)
|
and in PR 77425 we had an instance of this hidden behind a
macro, which the diagnostic complains about as follows:
deref-before-check-pr77425.c: In function 'get_odr_type':
deref-before-check-pr77425.c:35:10: warning: check of 'odr_types_ptr' for
NULL after already dereferencing it [-Wanalyzer-deref-before-check]
35 | if (odr_types_ptr)
| ^
'get_odr_type': events 1-3
|
| 27 | if (cond)
| | ^
| | |
| | (1) following 'false' branch...
|..
| 31 | else if (other_cond)
| | ~~~
| | ||
| | |(2) ...to here
| | (3) following 'true' branch...
|
'get_odr_type': event 4
|
| 11 | #define odr_types (*odr_types_ptr)
| | ~^~~
| ||
| |(4) ...to here
deref-before-check-pr77425.c:33:7: note: in expansion of macro 'odr_types'
| 33 | odr_types[val->id] = 0;
| | ^
|
'get_odr_type': event 5
|
| 11 | #define odr_types (*odr_types_ptr)
| | ~^~~
| ||
| |(5) pointer 'odr_types_ptr' is dereferenced
here
deref-before-check-pr77425.c:33:7: note: in expansion of macro 'odr_types'
| 33 | odr_types[val->id] = 0;
| | ^
|
'get_odr_type': event 6
|
| 35 | if (odr_types_ptr)
| | ^
| | |
| | (6) pointer 'odr_types_ptr' is checked for NULL here
but it was already dereferenced at (5)
|
gcc/analyzer/ChangeLog:
PR analyzer/99671
* analyzer.opt (Wanalyzer-deref-before-check): New warning.
* diagnostic-manager.cc
(null_assignment_sm_context::set_next_state): Only add state
change events for transition to "null" state.
(null_assignment_sm_context::is_transition_to_null): New.
* engine.cc (impl_region_model_context::on_pop_frame): New.
* exploded-graph.h (impl_region_model_context::on_pop_frame): New
decl.
* program-state.cc (sm_state_map::clear_any_state): New.
(sm_state_map::can_merge_with_p): New.
(program_state::can_merge_with_p): Replace requirement that
sm-states be equal in favor of an attempt to merge them.
* program-state.h (sm_state_map::clear_any_state): New decl.
(sm_state_map::can_merge_with_p): New decl.
* region-model.cc (region_model::eval_condition): Make const.
(region_model::pop_frame): Call ctxt->on_pop_frame.
* region-model.h (region_model::eval_condition): Make const.
(region_model_context::on_pop_frame): New vfunc.
(noop_region_model_context::on_pop_frame): New.
(region_model_context_decorator::on_pop_frame): New.
* sm-malloc.cc (enum resource_state): Add RS_ASSUMED_NON_NULL.
(allocation_state::dump_to_pp): Drop "final".
(struct assumed_non_null_state): New subclass.
(malloc_state_machine::m_assumed_non_null): New.
(assumed_non_null_p): New.
(class deref_before_check): New.
(assumed_non_null_state::dump_to_pp): New.
(malloc_state_machine::get_or_create_assumed_non_null_state_for_frame):
