From 1925a70f7e6472dc5df8f6f4e1d69227f5255859 Mon Sep 17 00:00:00 2001
From: "tree-sitter-ci-bot[bot]"
 <180118140+tree-sitter-ci-bot[bot]@users.noreply.github.com>
Date: Mon, 17 Feb 2025 18:52:32 -0800
Subject: [PATCH] Reset result_symbol field of lexer in wasm memory in between
 invocations (#4218) (#4220)

(cherry picked from commit 2bd400dcee06e5965e3c83c56b27ac8459c09860)

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
---
 lib/src/wasm_store.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/lib/src/wasm_store.c b/lib/src/wasm_store.c
index 3579fa6b..7a4320a0 100644
--- a/lib/src/wasm_store.c
+++ b/lib/src/wasm_store.c
@@ -1613,13 +1613,22 @@ static void ts_wasm_store__call(
   }
 }
 
+// The data fields of TSLexer, without the function pointers.
+//
+// This portion of the struct needs to be copied in and out
+// of wasm memory before and after calling a scan function.
+typedef struct {
+  int32_t lookahead;
+  TSSymbol result_symbol;
+} TSLexerDataPrefix;
+
 static bool ts_wasm_store__call_lex_function(TSWasmStore *self, unsigned function_index, TSStateId state) {
   wasmtime_context_t *context = wasmtime_store_context(self->store);
   uint8_t *memory_data = wasmtime_memory_data(context, &self->memory);
   memcpy(
     &memory_data[self->lexer_address],
-    &self->current_lexer->lookahead,
-    sizeof(self->current_lexer->lookahead)
+    self->current_lexer,
+    sizeof(TSLexerDataPrefix)
   );
 
   wasmtime_val_raw_t args[2] = {
@@ -1631,9 +1640,9 @@ static bool ts_wasm_store__call_lex_function(TSWasmStore *self, unsigned functio
   bool result = args[0].i32;
 
   memcpy(
-    &self->current_lexer->lookahead,
+    self->current_lexer,
     &memory_data[self->lexer_address],
-    sizeof(self->current_lexer->lookahead) + sizeof(self->current_lexer->result_symbol)
+    sizeof(TSLexerDataPrefix)
   );
   return result;
 }
@@ -1678,8 +1687,8 @@ bool ts_wasm_store_call_scanner_scan(
 
   memcpy(
     &memory_data[self->lexer_address],
-    &self->current_lexer->lookahead,
-    sizeof(self->current_lexer->lookahead)
+    self->current_lexer,
+    sizeof(TSLexerDataPrefix)
   );
 
   uint32_t valid_tokens_address =
@@ -1694,9 +1703,9 @@ bool ts_wasm_store_call_scanner_scan(
   if (self->has_error) return false;
 
   memcpy(
-    &self->current_lexer->lookahead,
+    self->current_lexer,
     &memory_data[self->lexer_address],
-    sizeof(self->current_lexer->lookahead) + sizeof(self->current_lexer->result_symbol)
+    sizeof(TSLexerDataPrefix)
   );
   return args[0].i32;
 }