second attempt at correcting fopen (hangs when trying to read from a dir)

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index 83f6c8112edf0732e4de957779e393d13d2deda3..7082589298398e1b9eff864acdef3120bf591c77 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -37,6 +37,7 @@
 #include <sys/resource.h>
 #include <sys/time.h>
 #include <sys/types.h>
+#include <sys/stat.h>
 
 #include <arpa/inet.h>
 #include <netinet/in.h>
@@ -130,7 +131,14 @@ int OS::GetLastError() {
 //
 
 FILE* OS::FOpen(const char* path, const char* mode) {
-  return fopen(path, mode);
+  FILE* file = fopen(path, mode);
+  if (file == NULL) return NULL;
+  struct stat file_stat;
+  if (fstat(fileno(file), &file_stat) != 0) return NULL;
+  bool is_regular_file = ((file_stat.st_mode & S_IFREG) != 0);
+  if (is_regular_file) return file;
+  fclose(file);
+  return NULL;
 }