From 691679a7905933a5677c3aa66cd87efe33d86c49 Mon Sep 17 00:00:00 2001
From: Will Holen <willholen@fb.com>
Date: Tue, 23 Jul 2019 17:39:49 -0700
Subject: [PATCH] Improve error message when registering empty bundles

Summary:
This change lets `registerBundle(bundleId, file)` throw an exception
when the file is empty, improving on the current behavior of an
eventual SIGABRT saying "MAP_FAILED: Invalid argument"

Reviewed By: ridiculousfish

Differential Revision: D16451938

fbshipit-source-id: b8b2d0bfed476319c379122fad59a5bf0a8c813b
---
 ReactCommon/cxxreact/JSBigString.cpp             | 3 +++
 ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/ReactCommon/cxxreact/JSBigString.cpp b/ReactCommon/cxxreact/JSBigString.cpp
index 325ac35325..57baa28339 100644
--- a/ReactCommon/cxxreact/JSBigString.cpp
+++ b/ReactCommon/cxxreact/JSBigString.cpp
@@ -110,6 +110,9 @@ static off_t maybeRemap(char *data, size_t size, int fd) {
 #endif // WITH_FBREMAP
 
 const char *JSBigFileString::c_str() const {
+  if (m_size == 0) {
+    return "";
+  }
   if (!m_data) {
     m_data =
       (const char *) mmap(0, m_size, PROT_READ, MAP_PRIVATE, m_fd, m_mapOff);
diff --git a/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp b/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
index 351d26fe06..e261dc574b 100644
--- a/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
+++ b/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
@@ -161,6 +161,10 @@ void JSIExecutor::registerBundle(
     bundleRegistry_->registerBundle(bundleId, bundlePath);
   } else {
     auto script = JSBigFileString::fromPath(bundlePath);
+    if (script->size() == 0) {
+      throw std::invalid_argument(
+          "Empty bundle registered with ID " + tag + " from " + bundlePath);
+    }
     runtime_->evaluateJavaScript(
         std::make_unique<BigStringBuffer>(std::move(script)),
         JSExecutor::getSyntheticBundlePath(bundleId, bundlePath));