analyzer: Fix regression bug after r14-1632-g9589a46ddadc8b [PR110198]

g++.dg/analyzer/PR100244.C was failing after a patch of PR109439.
The reason was a spurious preemptive return of get_store_value upon
out-of-bounds read that was preventing further checks. Now instead,
a boolean value check_poisoned goes to false when a OOB is detected,
and is later on given to get_or_create_initial_value.

gcc/analyzer/ChangeLog:
	PR analyzer/110198
	* region-model-manager.cc
	(region_model_manager::get_or_create_initial_value): Take an
	optional boolean value to bypass poisoning checks
	* region-model-manager.h: Update declaration of the above function.
	* region-model.cc (region_model::get_store_value): No longer returns
	on OOB, but rather gives a boolean to get_or_create_initial_value.
	(region_model::check_region_access): Update docstring.
	(region_model::check_region_for_write): Update docstring.

Signed-off-by: benjamin priour <priour.be@gmail.com>

3 files changed, 13 insertions, 10 deletions

diff --git a/gcc/analyzer/region-model-manager.cc b/gcc/analyzer/region-model-manager.cc
index 1453acf..4f11ef4 100644
--- a/gcc/analyzer/region-model-manager.cc
+++ b/gcc/analyzer/region-model-manager.cc
@@ -293,9 +293,10 @@ region_model_manager::create_unique_svalue (tree type)
    necessary.  */
 
 const svalue *
-region_model_manager::get_or_create_initial_value (const region *reg)
+region_model_manager::get_or_create_initial_value (const region *reg,
+						   bool check_poisoned)
 {
-  if (!reg->can_have_initial_svalue_p ())
+  if (!reg->can_have_initial_svalue_p () && check_poisoned)
     return get_or_create_poisoned_svalue (POISON_KIND_UNINIT,
 					  reg->get_type ());
 
diff --git a/gcc/analyzer/region-model-manager.h b/gcc/analyzer/region-model-manager.h
index 3340c3e..ff5333b 100644
--- a/gcc/analyzer/region-model-manager.h
+++ b/gcc/analyzer/region-model-manager.h
@@ -49,7 +49,8 @@ public:
 					     tree type);
   const svalue *get_or_create_poisoned_svalue (enum poison_kind kind,
 					       tree type);
-  const svalue *get_or_create_initial_value (const region *reg);
+  const svalue *get_or_create_initial_value (const region *reg,
+					     bool check_poisoned = true);
   const svalue *get_ptr_svalue (tree ptr_type, const region *pointee);
   const svalue *get_or_create_unaryop (tree type, enum tree_code op,
 				       const svalue *arg);
diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index 6bc60f8..187013a 100644
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -2373,8 +2373,9 @@ region_model::get_store_value (const region *reg,
   if (reg->empty_p ())
     return m_mgr->get_or_create_unknown_svalue (reg->get_type ());
 
+  bool check_poisoned = true;
   if (check_region_for_read (reg, ctxt))
-    return m_mgr->get_or_create_unknown_svalue(reg->get_type());
+    check_poisoned = false;
 
   /* Special-case: handle var_decls in the constant pool.  */
   if (const decl_region *decl_reg = reg->dyn_cast_decl_region ())
@@ -2427,7 +2428,7 @@ region_model::get_store_value (const region *reg,
       == RK_GLOBALS)
     return get_initial_value_for_global (reg);
 
-  return m_mgr->get_or_create_initial_value (reg);
+  return m_mgr->get_or_create_initial_value (reg, check_poisoned);
 }
 
 /* Return false if REG does not exist, true if it may do.
@@ -2790,7 +2791,7 @@ region_model::get_string_size (const region *reg) const
 
 /* If CTXT is non-NULL, use it to warn about any problems accessing REG,
    using DIR to determine if this access is a read or write.
-   Return TRUE if an UNKNOWN_SVALUE needs be created.
+   Return TRUE if an OOB access was detected.
    If SVAL_HINT is non-NULL, use it as a hint in diagnostics
    about the value that would be written to REG.  */
 
@@ -2804,10 +2805,10 @@ region_model::check_region_access (const region *reg,
   if (!ctxt)
     return false;
 
-  bool need_unknown_sval = false;
+  bool oob_access_detected = false;
   check_region_for_taint (reg, dir, ctxt);
   if (!check_region_bounds (reg, dir, sval_hint, ctxt))
-    need_unknown_sval = true;
+    oob_access_detected = true;
 
   switch (dir)
     {
@@ -2820,7 +2821,7 @@ region_model::check_region_access (const region *reg,
       check_for_writable_region (reg, ctxt);
       break;
     }
-  return need_unknown_sval;
+  return oob_access_detected;
 }
 
 /* If CTXT is non-NULL, use it to warn about any problems writing to REG.  */
@@ -2834,7 +2835,7 @@ region_model::check_region_for_write (const region *dest_reg,
 }
 
 /* If CTXT is non-NULL, use it to warn about any problems reading from REG.
-  Returns TRUE if an unknown svalue needs be created.  */
+  Returns TRUE if an OOB read was detected.  */
 
 bool
 region_model::check_region_for_read (const region *src_reg,