[wasm] Fix silent failure with --dump-wasm-module

The previous behavior failed silently if the file could not be opened
in the first place, and only wrote to stderr if writing failed after
opening the file successfully.

Change-Id: I1d1058134efd9298b60b65191ed6334de24d3f52
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1972886Reviewed-by: Bill Budge <bbudge@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65875}

src/wasm/module-decoder.cc

@@ -291,14 +291,15 @@ class ModuleDecoderImpl : public Decoder {
     size_t hash = base::hash_range(module_bytes.begin(), module_bytes.end());
     EmbeddedVector<char, 32> buf;
     SNPrintF(buf, "%016zx.%s.wasm", hash, ok() ? "ok" : "failed");
-    std::string name(buf.begin());
-    if (FILE* wasm_file = base::OS::FOpen((path + name).c_str(), "wb")) {
-      if (fwrite(module_bytes.begin(), module_bytes.length(), 1, wasm_file) !=
-          1) {
-        OFStream os(stderr);
-        os << "Error while dumping wasm file" << std::endl;
-      }
-      fclose(wasm_file);
+    path += buf.begin();
+    size_t rv = 0;
+    if (FILE* file = base::OS::FOpen(path.c_str(), "wb")) {
+      rv = fwrite(module_bytes.begin(), module_bytes.length(), 1, file);
+      fclose(file);
+    }
+    if (rv != 1) {
+      OFStream os(stderr);
+      os << "Error while dumping wasm file to " << path << std::endl;
     }
   }