diff --git a/src/library.js b/src/library.js
index 4702f1f5c1d1b..f7aff0cfd95b4 100644
--- a/src/library.js
+++ b/src/library.js
@@ -1899,7 +1899,7 @@ mergeInto(LibraryManager.library, {
       {{{ makeSetValue('ai', C_STRUCTS.addrinfo.ai_family, 'family', 'i32') }}};
       {{{ makeSetValue('ai', C_STRUCTS.addrinfo.ai_socktype, 'type', 'i32') }}};
       {{{ makeSetValue('ai', C_STRUCTS.addrinfo.ai_protocol, 'proto', 'i32') }}};
-      {{{ makeSetValue('ai', C_STRUCTS.addrinfo.ai_canonname, 'canon', 'i32') }}};
+      {{{ makeSetValue('ai', C_STRUCTS.addrinfo.ai_canonname, 'canon', '*') }}};
       {{{ makeSetValue('ai', C_STRUCTS.addrinfo.ai_addr, 'sa', '*') }}};
       if (family === {{{ cDefs.AF_INET6 }}}) {
         {{{ makeSetValue('ai', C_STRUCTS.addrinfo.ai_addrlen, C_STRUCTS.sockaddr_in6.__size__, 'i32') }}};
diff --git a/src/parseTools.js b/src/parseTools.js
index 299c7b40facd2..a3d951edba9ed 100644
--- a/src/parseTools.js
+++ b/src/parseTools.js
@@ -205,13 +205,13 @@ function makeInlineCalculation(expression, value, tempVar) {
 
 // Splits a number (an integer in a double, possibly > 32 bits) into an i64
 // value, represented by a low and high i32 pair.
-// Will suffer from rounding.
+// Will suffer from rounding and truncation.
 function splitI64(value) {
   // general idea:
   //
   //  $1$0 = ~~$d >>> 0;
   //  $1$1 = Math.abs($d) >= 1 ? (
-  //     $d > 0 ? Math.floor(($d)/ 4294967296.0) >>> 0,
+  //     $d > 0 ? Math.floor(($d)/ 4294967296.0) >>> 0
   //            : Math.ceil(Math.min(-4294967296.0, $d - $1$0)/ 4294967296.0)
   //  ) : 0;
   //
@@ -357,12 +357,22 @@ function makeGetValue(ptr, pos, type, noNeedFirst, unsigned, ignore, align) {
  * @return {string} JS code for performing the memory set operation
  */
 function makeSetValue(ptr, pos, value, type) {
+  var rtn = makeSetValueImpl(ptr, pos, value, type);
+  if (ASSERTIONS == 2 && (type.startsWith('i') || type.startsWith('u'))) {
+    const width = getBitWidth(type);
+    const assertion = `checkInt${width}(${value})`;
+    rtn += ';' + assertion
+  }
+  return rtn;
+}
+
+function makeSetValueImpl(ptr, pos, value, type) {
   if (type == 'i64' && !WASM_BIGINT) {
     // If we lack BigInt support we must fall back to an reading a pair of I32
     // values.
     return '(tempI64 = [' + splitI64(value) + '], ' +
-            makeSetValue(ptr, pos, 'tempI64[0]', 'i32') + ',' +
-            makeSetValue(ptr, getFastValue(pos, '+', getNativeTypeSize('i32')), 'tempI64[1]', 'i32') + ')';
+            makeSetValueImpl(ptr, pos, 'tempI64[0]', 'i32') + ',' +
+            makeSetValueImpl(ptr, getFastValue(pos, '+', getNativeTypeSize('i32')), 'tempI64[1]', 'i32') + ')';
   }
 
   const offset = calcFastOffset(ptr, pos);
@@ -442,6 +452,12 @@ function calcFastOffset(ptr, pos) {
   return getFastValue(ptr, '+', pos);
 }
 
+function getBitWidth(type) {
+  if (type == 'i53' || type == 'u53')
+    return 53;
+  return getNativeTypeSize(type) * 8;
+}
+
 function getHeapForType(type) {
   assert(type);
   if (isPointerType(type)) {
diff --git a/src/runtime_debug.js b/src/runtime_debug.js
index 5a627a2634561..c062e1c70ada6 100644
--- a/src/runtime_debug.js
+++ b/src/runtime_debug.js
@@ -95,7 +95,37 @@ function unexportedRuntimeSymbol(sym) {
     });
   }
 }
-#endif
+
+#if ASSERTIONS == 2
+
+var MAX_UINT8  = (2 **  8) - 1;
+var MAX_UINT16 = (2 ** 16) - 1;
+var MAX_UINT32 = (2 ** 32) - 1;
+var MAX_UINT53 = (2 ** 53) - 1;
+var MAX_UINT64 = (2 ** 64) - 1;
+
+var MIN_INT8  = - (2 ** ( 8 - 1)) + 1;
+var MIN_INT16 = - (2 ** (16 - 1)) + 1;
+var MIN_INT32 = - (2 ** (32 - 1)) + 1;
+var MIN_INT53 = - (2 ** (53 - 1)) + 1;
+var MIN_INT64 = - (2 ** (64 - 1)) + 1;
+
+function checkInt(value, bits, min, max) {
+  assert(Number.isInteger(Number(value)), "attempt to write non-integer (" + value + ") into integer heap");
+  assert(value <= max, "value (" + value + ") too large to write as " + bits +"-bit value");
+  assert(value >= min, "value (" + value + ") too small to write as " + bits +"-bit value");
+}
+
+var checkInt1 = (value) => checkInt(value, 1, 1);
+var checkInt8 = (value) => checkInt(value, 8, MIN_INT8, MAX_UINT8);
+var checkInt16 = (value) => checkInt(value, 16, MIN_INT16, MAX_UINT16);
+var checkInt32 = (value) => checkInt(value, 32, MIN_INT32, MAX_UINT32);
+var checkInt53 = (value) => checkInt(value, 53, MIN_INT53, MAX_UINT53);
+var checkInt64 = (value) => checkInt(value, 64, MIN_INT64, MAX_UINT64);
+
+#endif // ASSERTIONS == 2
+
+#endif // ASSERTIONS
 
 #if RUNTIME_DEBUG
 var runtimeDebug = true; // Switch to false at runtime to disable logging at the right times
diff --git a/test/test_other.py b/test/test_other.py
index f3128024aad5b..d8e1916d2e203 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -12892,7 +12892,13 @@ def test_no_cfi(self):
 
   @also_with_wasm_bigint
   def test_parseTools(self):
-    self.do_other_test('test_parseTools.c', emcc_args=['--js-library', test_file('other/test_parseTools.js')])
+    self.emcc_args += ['--js-library', test_file('other/test_parseTools.js')]
+    self.do_other_test('test_parseTools.c')
+
+    # If we run ths same test with -sASSERTIONS=2 we expect it to fail because it
+    # involves writing numbers that are exceed the side of the type.
+    expected = 'Aborted(Assertion failed: value (316059037807746200000) too large to write as 64-bit value)'
+    self.do_runf(test_file('other/test_parseTools.c'), expected, emcc_args=['-sASSERTIONS=2'], assert_returncode=NON_ZERO)
 
   def test_lto_atexit(self):
     self.emcc_args.append('-flto')
@@ -13200,8 +13206,8 @@ def test_parseTools_legacy(self):
     create_file('lib.js', '''
       mergeInto(LibraryManager.library, {
         foo: function() {
-            return {{{ Runtime.POINTER_SIZE }}};
-          }
+          return {{{ Runtime.POINTER_SIZE }}};
+        }
       });
     ''')
     self.set_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE', 'foo')