fix(lib): address strict aliasing violations in TreeCursor type

.github/workflows/build.yml

@@ -211,7 +211,7 @@ jobs:
         make -j CFLAGS="$CFLAGS" CC=$CC AR=$AR
       env:
         PLATFORM: ${{ matrix.platform }}
-        CFLAGS: -g -Werror -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types
+        CFLAGS: -g -Werror -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types -Werror=strict-aliasing -Wstrict-aliasing=2
 
     - name: Build C library (CMake)
       if: "!matrix.cross && !matrix.vm"

.github/workflows/wasm_exports.yml

@@ -31,7 +31,7 @@ jobs:
       - name: Build C library (make)
         run: make -j CFLAGS="$CFLAGS"
         env:
-          CFLAGS: -g -Werror -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types
+          CFLAGS: -g -Werror -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types -Werror=strict-aliasing -Wstrict-aliasing=2
 
       - name: Build Wasm Library
         working-directory: lib/binding_web

CMakeLists.txt

@@ -33,7 +33,8 @@ if(MSVC)
 else()
   target_compile_options(tree-sitter PRIVATE
                          -Wall -Wextra -Wshadow -Wpedantic
-                         -Werror=incompatible-pointer-types)
+                         -Werror=incompatible-pointer-types
+                         -Werror=strict-aliasing -Wstrict-aliasing=2)
 endif()
 
 if(TREE_SITTER_FEATURE_WASM)

Makefile

@@ -22,7 +22,7 @@ OBJ := $(SRC:.c=.o)
 
 # define default flags, and override to append mandatory flags
 ARFLAGS := rcs
-CFLAGS ?= -O3 -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types
+CFLAGS ?= -O3 -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types -Werror=strict-aliasing -Wstrict-aliasing=2
 override CFLAGS += -std=c11 -fPIC -fvisibility=hidden
 override CFLAGS += -D_POSIX_C_SOURCE=200112L -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_DARWIN_C_SOURCE
 override CFLAGS += -Ilib/src -Ilib/src/wasm -Ilib/include

lib/src/tree_cursor.c

@@ -3,6 +3,11 @@
 #include "./language.h"
 #include "./tree.h"
 
+_Static_assert(
+  sizeof(TreeCursor) <= sizeof(TSTreeCursor),
+  "TreeCursor must fit within TSTreeCursor"
+);
+
 typedef struct {
   Subtree parent;
   const TSTree *tree;
@@ -153,8 +158,10 @@ static inline bool ts_tree_cursor_child_iterator_previous(
 // TSTreeCursor - lifecycle
 
 TSTreeCursor ts_tree_cursor_new(TSNode node) {
-  TSTreeCursor self = {NULL, NULL, {0, 0, 0}};
-  ts_tree_cursor_init((TreeCursor *)&self, node);
+  TreeCursor cursor = {0};
+  ts_tree_cursor_init(&cursor, node);
+  TSTreeCursor self = {0};
+  memcpy(&self, &cursor, sizeof(cursor));
   return self;
 }
 
@@ -697,12 +704,13 @@ const char *ts_tree_cursor_current_field_name(const TSTreeCursor *_self) {
 
 TSTreeCursor ts_tree_cursor_copy(const TSTreeCursor *_cursor) {
   const TreeCursor *cursor = (const TreeCursor *)_cursor;
-  TSTreeCursor res = {NULL, NULL, {0, 0}};
-  TreeCursor *copy = (TreeCursor *)&res;
-  copy->tree = cursor->tree;
-  copy->root_alias_symbol = cursor->root_alias_symbol;
-  array_init(&copy->stack);
-  array_push_all(&copy->stack, &cursor->stack);
+  TreeCursor copy = {0};
+  copy.tree = cursor->tree;
+  copy.root_alias_symbol = cursor->root_alias_symbol;
+  array_init(&copy.stack);
+  array_push_all(&copy.stack, &cursor->stack);
+  TSTreeCursor res = {0};
+  memcpy(&res, &copy, sizeof(copy));
   return res;
 }