Merge branch 'metsw24-max-mmap-map-failed-guard'

httplib.h

@@ -5576,6 +5576,14 @@ inline bool mmap::open(const char *path) {
     is_open_empty_file = true;
     return false;
   }
+
+  if (addr_ == MAP_FAILED) {
+    // Clear the sentinel before `close()`, since `is_open()` only checks
+    // `addr_` against nullptr and `munmap()` must not be called with it.
+    addr_ = nullptr;
+    close();
+    return false;
+  }
 #endif
 
   return true;

test/test.cc

@@ -9346,6 +9346,23 @@ TEST(MmapTest, OpenWhileFileHeldForWriting) {
 }
 #endif
 
+#ifndef _WIN32
+// A failed ::mmap() must not be reported as an open mapping, otherwise data()
+// hands the caller the MAP_FAILED sentinel. A directory is the easiest way to
+// reach it, since ::open() and fstat() succeed for one but ::mmap() doesn't.
+TEST(MmapTest, FailedMappingIsNotOpen) {
+  const char *path = "./mmap_failed_mapping_test_dir";
+  ASSERT_EQ(0, ::mkdir(path, 0755));
+  auto dir_cleanup = detail::scope_exit([&] { ::rmdir(path); });
+
+  detail::mmap m(path);
+  EXPECT_FALSE(m.is_open());
+  EXPECT_EQ(0U, m.size());
+  EXPECT_NE(static_cast<const void *>(m.data()),
+            static_cast<const void *>(MAP_FAILED));
+}
+#endif
+
 TEST(KeepAliveTest, ReadTimeout) {
   Server svr;