Guard against some possible null pointer dereferences

Found by gcc 12 when compiling with "-O2 -Wnull-dereference"

bindings/guile/gnc-kvp-guile.cpp

@@ -121,7 +121,7 @@ gnc_kvp_value_ptr_to_scm(KvpValue* val)
     case KvpValue::Type::GUID:
     {
         auto tempguid = val->get<GncGUID*>();
-        return gnc_guid2scm(*tempguid);
+        return tempguid ? gnc_guid2scm(*tempguid) : SCM_BOOL_F;
     }
     break;
     case KvpValue::Type::FRAME:
@@ -133,7 +133,7 @@ gnc_kvp_value_ptr_to_scm(KvpValue* val)
             auto val_scm { gnc_kvp_value_ptr_to_scm (iter.second) };
             return scm_acons (key_scm, val_scm, rv);
         };
-        return scm_reverse (std::accumulate (frame->begin(), frame->end(), SCM_EOL, acc));
+        return frame ? scm_reverse (std::accumulate (frame->begin(), frame->end(), SCM_EOL, acc)) : SCM_BOOL_F;
     }
     break;
     case KvpValue::Type::GLIST:

gnucash/gnome-search/search-core-type.c

@@ -230,7 +230,9 @@ editable_enters (GNCSearchCoreType *fe)
 void
 gnc_search_core_register_type (const char *type_name, GNCSearchCoreNew fcn)
 {
-    g_return_if_fail (type_name || *type_name || fcn);
+    g_return_if_fail (type_name);
+    g_return_if_fail (*type_name);
+    g_return_if_fail (fcn);
     g_return_if_fail (typeTable);
 
     g_hash_table_insert (typeTable, (char *) type_name, (gpointer) fcn);

gnucash/gnome/gnc-plugin-page-owner-tree.c

@@ -932,7 +932,11 @@ static int build_owner_report (GncOwner *owner, Account *acc)
         args = scm_cons (SCM_BOOL_F, args);
     }
 
-    arg = SWIG_NewPointerObj(owner, SWIG_TypeQuery("_p__gncOwner"), 0);
+    swig_type_info * qtype = SWIG_TypeQuery("_p__gncOwner");
+    g_return_val_if_fail (qtype, -1);
+
+    arg = SWIG_NewPointerObj(owner, qtype, 0);
+
     g_return_val_if_fail (arg != SCM_UNDEFINED, -1);
     args = scm_cons (arg, args);
 

gnucash/report/gnc-report.cpp

@@ -411,6 +411,9 @@ gnc_get_optiondb_from_dispatcher(SCM dispatcher)
         else
             c_ptr = reinterpret_cast<void*>(SCM_CELL_WORD_1(smob));
     }
+    else
+        return nullptr;
+
     auto u_ptr{static_cast<std::unique_ptr<GncOptionDB>*>(c_ptr)};
     return u_ptr->get();
 }

libgnucash/app-utils/calculation/expression_parser.c

@@ -612,8 +612,11 @@ parse_string (var_store_ptr value, const char *string, parser_env_ptr pe)
             var_store_ptr val;
 
             val = pop (pe);
-            pe->negate_numeric (val->value);
-            push (val, pe);
+            if (val)
+            {
+                pe->negate_numeric (val->value);
+                push (val, pe);
+            }
         }
     }
 

libgnucash/engine/gnc-date.cpp

@@ -731,6 +731,8 @@ qof_scan_date_internal (const char *buff, int *day, int *month, int *year,
     /* today's date */
     gnc_time (&secs);
     now = gnc_localtime (&secs);
+    if (!now)
+        return FALSE;
     now_day = now->tm_mday;
     now_month = now->tm_mon + 1;
     now_year = now->tm_year + 1900;

libgnucash/engine/qofquery.cpp

@@ -1208,7 +1208,8 @@ qof_query_merge(QofQuery *q1, QofQuery *q2, QofQueryOp op)
         break;
     }
 
-    retval->search_for = search_for;
+    if (retval)
+        retval->search_for = search_for;
     return retval;
 }