More misc ASAN fixes (#1882)

* fix buffer overflow in simple_ast.h printing.
* check wasm binary format reading of function export indexes for errors.
* check if s-expr format imports have a non-empty module and base.

Fixes #1876
Fixes #1877
Fixes #1879

2 files changed, 5 insertions, 0 deletions

diff --git a/src/emscripten-optimizer/istring.h b/src/emscripten-optimizer/istring.h
index 5a7d05162..5c3b094c3 100644
--- a/src/emscripten-optimizer/istring.h
+++ b/src/emscripten-optimizer/istring.h
@@ -149,6 +149,10 @@ struct IString {
   bool startsWith(const char *prefix) const {
     return stripPrefix(prefix) != nullptr;
   }
+
+  size_t size() const {
+    return str ? strlen(str) : 0;
+  }
 };
 
 } // namespace cashew
diff --git a/src/emscripten-optimizer/simple_ast.h b/src/emscripten-optimizer/simple_ast.h
index de8122ba1..f38377e70 100644
--- a/src/emscripten-optimizer/simple_ast.h
+++ b/src/emscripten-optimizer/simple_ast.h
@@ -561,6 +561,7 @@ struct JSPrinter {
 
   void printAst() {
     print(ast);
+    ensure(1);
     buffer[used] = 0;
   }