analyzer: reimplement -Wanalyzer-use-of-uninitialized-value [PR95006 et al]

The initial gcc 10 era commit of the analyzer (in
757bf1dff5e8cee34c0a75d06140ca972bfecfa7) had an implementation of
-Wanalyzer-use-of-uninitialized-value, but was sufficiently buggy
that I removed it in 78b9783774bfd3540f38f5b1e3c7fc9f719653d7 before
the release of gcc 10.1

This patch reintroduces the warning, heavily rewritten, with (I hope)
a less buggy implementation this time, for GCC 12.

gcc/analyzer/ChangeLog:
	PR analyzer/95006
	PR analyzer/94713
	PR analyzer/94714
	* analyzer.cc (maybe_reconstruct_from_def_stmt): Split out
	GIMPLE_ASSIGN case into...
	(get_diagnostic_tree_for_gassign_1): New.
	(get_diagnostic_tree_for_gassign): New.
	* analyzer.h (get_diagnostic_tree_for_gassign): New decl.
	* analyzer.opt (Wanalyzer-write-to-string-literal): New.
	* constraint-manager.cc (class svalue_purger): New.
	(constraint_manager::purge_state_involving): New.
	* constraint-manager.h
	(constraint_manager::purge_state_involving): New.
	* diagnostic-manager.cc (saved_diagnostic::supercedes_p): New.
	(dedupe_winners::handle_interactions): New.
	(diagnostic_manager::emit_saved_diagnostics): Call it.
	* diagnostic-manager.h (saved_diagnostic::supercedes_p): New decl.
	* engine.cc (impl_region_model_context::warn): Convert return type
	to bool.  Return false if the diagnostic isn't saved.
	(impl_region_model_context::purge_state_involving): New.
	(impl_sm_context::get_state): Use NULL ctxt when querying old
	rvalue.
	(impl_sm_context::set_next_state): Use new sval when querying old
	state.
	(class dump_path_diagnostic): Move to region-model.cc
	(exploded_node::on_stmt): Move to on_stmt_pre and on_stmt_post.
	Remove call to purge_state_involving.
	(exploded_node::on_stmt_pre): New, based on the above.  Move most
	of it to region_model::on_stmt_pre.
	(exploded_node::on_stmt_post): Likewise, moving to
	region_model::on_stmt_post.
	(class stale_jmp_buf): Fix parent class to use curiously recurring
	template pattern.
	(feasibility_state::maybe_update_for_edge): Call on_call_pre and
	on_call_post on gcalls.
	* exploded-graph.h (impl_region_model_context::warn): Return bool.
	(impl_region_model_context::purge_state_involving): New decl.
	(exploded_node::on_stmt_pre): New decl.
	(exploded_node::on_stmt_post): New decl.
	* pending-diagnostic.h (pending_diagnostic::use_of_uninit_p): New.
	(pending_diagnostic::supercedes_p): New.
	* program-state.cc (sm_state_map::get_state): Inherit state for
	conjured_svalue as well as initial_svalue.
	(sm_state_map::purge_state_involving): Also support SK_CONJURED.
	* region-model-impl-calls.cc (call_details::get_uncertainty):
	Handle m_ctxt being NULL.
	(call_details::get_or_create_conjured_svalue): New.
	(region_model::impl_call_fgets): New.
	(region_model::impl_call_fread): New.
	* region-model-manager.cc
	(region_model_manager::get_or_create_initial_value): Return an
	uninitialized poisoned value for regions that can't have initial
	values.
	* region-model-reachability.cc
	(reachable_regions::mark_escaped_clusters): Handle ctxt being
	NULL.
	* region-model.cc (region_to_value_map::purge_state_involving): New.
	(poisoned_value_diagnostic::use_of_uninit_p): New.
	(poisoned_value_diagnostic::emit): Handle POISON_KIND_UNINIT.
	(poisoned_value_diagnostic::describe_final_event): Likewise.
	(region_model::check_for_poison): New.
	(region_model::on_assignment): Call it.
	(class dump_path_diagnostic): Move here from engine.cc.
	(region_model::on_stmt_pre): New, based on exploded_node::on_stmt.
	(region_model::on_call_pre): Move the setting of the LHS to a
	conjured svalue to before the checks for specific functions.
	Handle "fgets", "fgets_unlocked", and "fread".
	(region_model::purge_state_involving): New.
	(region_model::handle_unrecognized_call): Handle ctxt being NULL.
	(region_model::get_rvalue): Call check_for_poison.
	(selftest::test_stack_frames): Use NULL for context when getting
	uninitialized rvalue.
	(selftest::test_alloca): Likewise.
	* region-model.h (region_to_value_map::purge_state_involving): New
	decl.
	(call_details::get_or_create_conjured_svalue): New decl.
	(region_model::on_stmt_pre): New decl.
	(region_model::purge_state_involving): New decl.
	(region_model::impl_call_fgets): New decl.
	(region_model::impl_call_fread): New decl.
	(region_model::check_for_poison): New decl.
	(region_model_context::warn): Return bool.
	(region_model_context::purge_state_involving): New.
	(noop_region_model_context::warn): Return bool.
	(noop_region_model_context::purge_state_involving): New.
	(test_region_model_context:: warn): Return bool.
	* region.cc (region::get_memory_space): New.
	(region::can_have_initial_svalue_p): New.
	(region::involves_p): New.
	* region.h (enum memory_space): New.
	(region::get_memory_space): New decl.
	(region::can_have_initial_svalue_p): New decl.
	(region::involves_p): New decl.
	* sm-malloc.cc (use_after_free::supercedes_p): New.
	* store.cc (binding_cluster::purge_state_involving): New.
	(store::purge_state_involving): New.
	* store.h (class symbolic_binding): New forward decl.
	(binding_key::dyn_cast_symbolic_binding): New.
	(symbolic_binding::dyn_cast_symbolic_binding): New.
	(binding_cluster::purge_state_involving): New.
	(store::purge_state_involving): New.
	* svalue.cc (svalue::can_merge_p): Reject attempts to merge
	poisoned svalues with other svalues, so that we identify
	paths in which a variable is conditionally uninitialized.
	(involvement_visitor::visit_conjured_svalue): New.
	(svalue::involves_p): Also handle SK_CONJURED.
	(poison_kind_to_str): Handle POISON_KIND_UNINIT.
	(poisoned_svalue::maybe_fold_bits_within): New.
	* svalue.h (enum poison_kind): Add POISON_KIND_UNINIT.
	(poisoned_svalue::maybe_fold_bits_within): New decl.

gcc/ChangeLog:
	PR analyzer/95006
	PR analyzer/94713
	PR analyzer/94714
	* doc/invoke.texi: Add -Wanalyzer-use-of-uninitialized-value.

gcc/testsuite/ChangeLog:
	PR analyzer/95006
	PR analyzer/94713
	PR analyzer/94714
	* g++.dg/analyzer/pr93212.C: Update location of warning.
	* g++.dg/analyzer/pr94011.C: Add
	-Wno-analyzer-use-of-uninitialized-value.
	* g++.dg/analyzer/pr94503.C: Likewise.
	* gcc.dg/analyzer/clobbers-1.c: Convert "f" from a local to a
	param to avoid uninitialized warning.
	* gcc.dg/analyzer/data-model-1.c (test_12): Add test for
	uninitialized value on result of alloca.
	(test_12a): Add expected warning.
	(test_12c): Likewise.
	(test_19): Likewise.
	(test_29b): Likewise.
	(test_29c): Likewise.
	(test_37): Remove xfail.
	(test_37a): Likewise.
	* gcc.dg/analyzer/data-model-20.c: Add warning about leak.
	* gcc.dg/analyzer/explode-2.c: Remove params; add
	-Wno-analyzer-too-complex, -Wno-analyzer-malloc-leak, and xfails.
	Initialize the locals.
	* gcc.dg/analyzer/explode-2a.c: Initialize the locals.  Add
	expected leak.
	* gcc.dg/analyzer/fgets-1.c: New test.
	* gcc.dg/analyzer/fread-1.c: New test.
	* gcc.dg/analyzer/malloc-1.c (test_16): Add expected warning.
	(test_40): Likewise.
	* gcc.dg/analyzer/memset-CVE-2017-18549-1.c: Check for
	uninitialized padding.
	* gcc.dg/analyzer/pr93355-localealias-feasibility.c (fread): New
	decl.
	(read_alias_file): Call it.
	* gcc.dg/analyzer/pr94047.c: Add expected warnings.
	* gcc.dg/analyzer/pr94851-2.c: Likewise.
	* gcc.dg/analyzer/pr96841.c: Convert local to a param.
	* gcc.dg/analyzer/pr98628.c: Likewise.
	* gcc.dg/analyzer/pr99042.c: Updated expected location of leak
	diagnostics.
	* gcc.dg/analyzer/symbolic-1.c: Add expected warnings.
	* gcc.dg/analyzer/symbolic-7.c: Likewise.
	* gcc.dg/analyzer/torture/pr93649.c: Add expected warning.  Skip
	with -fno-fat-lto-objects.
	* gcc.dg/analyzer/uninit-1.c: New test.
	* gcc.dg/analyzer/uninit-2.c: New test.
	* gcc.dg/analyzer/uninit-3.c: New test.
	* gcc.dg/analyzer/uninit-4.c: New test.
	* gcc.dg/analyzer/uninit-pr94713.c: New test.
	* gcc.dg/analyzer/uninit-pr94714.c: New test.
	* gcc.dg/analyzer/use-after-free-2.c: New test.
	* gcc.dg/analyzer/use-after-free-3.c: New test.
	* gcc.dg/analyzer/zlib-3.c: Add expected warning.
	* gcc.dg/analyzer/zlib-6.c: Convert locals to params to avoid
	uninitialized warnings.  Remove xfail.
	* gcc.dg/analyzer/zlib-6a.c: New test, based on the old version
	of the above.
	* gfortran.dg/analyzer/pr97668.f: Add
	-Wno-analyzer-use-of-uninitialized-value and
	-Wno-analyzer-too-complex.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/gcc/analyzer/svalue.h b/gcc/analyzer/svalue.h
index 5552fcf..54b97f8 100644
--- a/gcc/analyzer/svalue.h
+++ b/gcc/analyzer/svalue.h
@@ -324,6 +324,9 @@ public:
 
 enum poison_kind
 {
+  /* For use to describe uninitialized memory.  */
+  POISON_KIND_UNINIT,
+
   /* For use to describe freed memory.  */
   POISON_KIND_FREED,
 
@@ -378,6 +381,11 @@ public:
   void dump_to_pp (pretty_printer *pp, bool simple) const FINAL OVERRIDE;
   void accept (visitor *v) const FINAL OVERRIDE;
 
+  const svalue *
+  maybe_fold_bits_within (tree type,
+			  const bit_range &subrange,
+			  region_model_manager *mgr) const FINAL OVERRIDE;
+
   enum poison_kind get_poison_kind () const { return m_kind; }
 
  private: