Open fstream files in O_CLOEXEC mode when possible.

Reviewers: EricWF, mclow.lists, ldionne

Reviewed By: ldionne

Subscribers: smeenai, dexonsmith, christof, ldionne, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D59839

llvm-svn: 372027
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: a7e9059967c4bff83ae6c3b595828bbbc8aaf82e
diff --git a/include/fstream b/include/fstream
index 7db9017..e913899 100644
--- a/include/fstream
+++ b/include/fstream
@@ -508,34 +508,34 @@
   switch (__mode & ~ios_base::ate) {
   case ios_base::out:
   case ios_base::out | ios_base::trunc:
-    return "w";
+    return "w" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::out | ios_base::app:
   case ios_base::app:
-    return "a";
+    return "a" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in:
-    return "r";
+    return "r" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out:
-    return "r+";
+    return "r+" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::trunc:
-    return "w+";
+    return "w+" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::app:
   case ios_base::in | ios_base::app:
-    return "a+";
+    return "a+" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::out | ios_base::binary:
   case ios_base::out | ios_base::trunc | ios_base::binary:
-    return "wb";
+    return "wb" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::out | ios_base::app | ios_base::binary:
   case ios_base::app | ios_base::binary:
-    return "ab";
+    return "ab" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::binary:
-    return "rb";
+    return "rb" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::binary:
-    return "r+b";
+    return "r+b" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::trunc | ios_base::binary:
-    return "w+b";
+    return "w+b" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::app | ios_base::binary:
   case ios_base::in | ios_base::app | ios_base::binary:
-    return "a+b";
+    return "a+b" _LIBCPP_FOPEN_CLOEXEC_MODE;
   default:
     return nullptr;
   }