Add ASAN poisoning to the arena

src/arena.hpp

@@ -1,6 +1,9 @@
 #pragma once
 
+#include <sanitizer/asan_interface.h>
+
 #include <concepts>
+#include <cstring>
 #include <iostream>
 
 #include "error.hpp"
@@ -81,15 +84,24 @@ class GcRootList {
 class ArenaHeap {
  public:
   ArenaHeap(uint8_t* buf, uint64_t bufsize)
-      : buf(buf), bufsize(bufsize), boundary(0) {}
+      : buf(buf), bufsize(bufsize), boundary(0) {
+    memset(buf, 0, bufsize);
+    ASAN_POISON_MEMORY_REGION(buf, bufsize);
+  }
 
   Result<void*> alloc(uint64_t size) {
     // Always align to 64 bits
     if (size % 8 != 0) size += 8 - size % 8;
 
-    if (boundary + size >= bufsize) return ErrorCode::OutOfMemory;
+    // padding for guard value
+    uint64_t boundary_size = 8;
+
+    if (boundary + size + boundary_size >= bufsize)
+      return ErrorCode::OutOfMemory;
     void* res = buf + boundary;
     boundary += size;
+    ASAN_UNPOISON_MEMORY_REGION(res, size);
+    boundary += boundary_size;
     return res;
   }
 
@@ -139,7 +151,7 @@ class StaticArenaHeap : public ArenaHeap {
 
  private:
   static const uint64_t heapsize = size - sizeof(ArenaHeap);
-  uint8_t _buf[heapsize]{0};
+  uint8_t _buf[heapsize];
 };
 
 template <uint64_t size>

src/vli.cpp

@@ -30,7 +30,7 @@ int main() {
   std::cout << "root count: " << arena.root_count() << "\n";
   */
 
-  auto s = DIEIF(String::create(arena, "(1 2 3 \"foo\")"));
+  auto s = DIEIF(String::create(arena, "(1 2 3 \"foo\" (xyz))"));
   auto reader = Reader(arena, s);
 
   auto r = DIEIF(reader.read_one());