Merge pull request CleverRaven#49906 from kevingranade/mm-stop-UB

Return an invalid mm_submap if the map_memory is not prepared

src/map_memory.cpp

@@ -45,6 +45,7 @@ struct reg_coord_pair {
 };
 
 mm_submap::mm_submap() = default;
+mm_submap::mm_submap( bool make_valid ) : valid( make_valid ) {}
 
 mm_region::mm_region() : submaps {{ nullptr }} {}
 
@@ -82,6 +83,9 @@ void map_memory::memorize_tile( const tripoint &pos, const std::string &ter,
 {
     coord_pair p( pos );
     mm_submap &sm = get_submap( p.sm );
+    if( !sm.is_valid() ) {
+        return;
+    }
     sm.set_tile( p.loc, memorized_terrain_tile{ ter, subtile, rotation } );
 }
 
@@ -96,13 +100,19 @@ void map_memory::memorize_symbol( const tripoint &pos, const int symbol )
 {
     coord_pair p( pos );
     mm_submap &sm = get_submap( p.sm );
+    if( !sm.is_valid() ) {
+        return;
+    }
     sm.set_symbol( p.loc, symbol );
 }
 
 void map_memory::clear_memorized_tile( const tripoint &pos )
 {
     coord_pair p( pos );
     mm_submap &sm = get_submap( p.sm );
+    if( !sm.is_valid() ) {
+        return;
+    }
     sm.set_symbol( p.loc, mm_submap::default_symbol );
     sm.set_tile( p.loc, mm_submap::default_tile );
 }
@@ -235,10 +245,15 @@ shared_ptr_fast<mm_submap> map_memory::load_submap( const tripoint &sm_pos )
 }
 
 static mm_submap null_mz_submap;
+static mm_submap invalid_mz_submap{ false };
 
 const mm_submap &map_memory::get_submap( const tripoint &sm_pos ) const
 {
-    point idx = ( sm_pos - cache_pos ).xy();
+    if( cache_pos == tripoint_min ) {
+        debugmsg( "Called map_memory with an " );
+        return invalid_mz_submap;
+    }
+    const point idx = ( sm_pos - cache_pos ).xy();
     if( idx.x > 0 && idx.y > 0 && idx.x < cache_size.x && idx.y < cache_size.y ) {
         return *cached[idx.y * cache_size.x + idx.x];
     } else {
@@ -248,7 +263,10 @@ const mm_submap &map_memory::get_submap( const tripoint &sm_pos ) const
 
 mm_submap &map_memory::get_submap( const tripoint &sm_pos )
 {
-    point idx = ( sm_pos - cache_pos ).xy();
+    if( cache_pos == tripoint_min ) {
+        return invalid_mz_submap;
+    }
+    const point idx = ( sm_pos - cache_pos ).xy();
     if( idx.x > 0 && idx.y > 0 && idx.x < cache_size.x && idx.y < cache_size.y ) {
         return *cached[idx.y * cache_size.x + idx.x];
     } else {

src/map_memory.h

@@ -34,12 +34,18 @@ struct mm_submap {
         static const int default_symbol;
 
         mm_submap();
+        explicit mm_submap( bool make_valid );
 
         /** Whether this mm_submap is empty. Empty submaps are skipped during saving. */
         bool is_empty() const {
             return tiles.empty() && symbols.empty();
         }
 
+        // Whether this mm_submap is invalid, i.e. returned from an uninitialized region.
+        bool is_valid() const {
+            return valid;
+        }
+
         inline const memorized_terrain_tile &tile( const point &p ) const {
             if( tiles.empty() ) {
                 return default_tile;
@@ -80,6 +86,7 @@ struct mm_submap {
     private:
         std::vector<memorized_terrain_tile> tiles; // holds either 0 or SEEX*SEEY elements
         std::vector<int> symbols; // holds either 0 or SEEX*SEEY elements
+        bool valid = true;
 };
 
 /**

tests/map_memory_test.cpp

@@ -66,6 +66,13 @@ TEST_CASE( "map_memory_overwrites", "[map_memory]" )
     CHECK( memory.get_symbol( p2 ) == 3 );
 }
 
+TEST_CASE( "map_memory_forgets", "[map_memory]" )
+{
+    map_memory memory;
+    memory.memorize_symbol( tripoint_zero, 1 );
+    memory.memorize_symbol( p3, 1 );
+}
+
 // TODO: map memory save / load
 
 #include <chrono>