Make M-x shell work in emacs.

ports/nacl-spawn/nacl_spawn.cc

Index: ports/nacl-spawn/nacl_spawn.cc
diff --git a/ports/nacl-spawn/nacl_spawn.cc b/ports/nacl-spawn/nacl_spawn.cc
index 59cd9a955dc0b8af195414c7a093b9e8601cf245..77a99fe03c9ef77fb3804335a1ab58e9c1c16e2c 100644
--- a/ports/nacl-spawn/nacl_spawn.cc
+++ b/ports/nacl-spawn/nacl_spawn.cc
@@ -354,7 +354,8 @@ static int CloneFileDescriptors(struct PP_Var envs_var) {
       char entry[100];
       snprintf(entry, sizeof entry,
           "NACL_SPAWN_FD_SETUP_%d=pipe:%d:%d:%d", count++, fd,
-          static_cast<int>(st.st_ino), st.st_rdev == O_WRONLY);
+          static_cast<int>(st.st_ino),
+          (st.st_rdev & O_WRONLY) == O_WRONLY);
       nspawn_array_appendstring(envs_var, entry);
     } else if (S_ISLNK(st.st_mode)) {
       // Unsupported.
@@ -689,6 +690,11 @@ void jseval(const char* cmd, char** data, size_t* len) {
 // Create a javascript pipe. pipefd[0] will be the read end of the pipe
 // and pipefd[1] the write end of the pipe.
 int nacl_spawn_pipe(int pipefd[2]) {
+  return nacl_spawn_pipe_flags(0, pipefd);
+}
+
+// Same as above with flags.
+int nacl_spawn_pipe_flags(int flags, int pipefd[2]) {
   if (pipefd == NULL) {
     errno = EFAULT;
     return -1;
@@ -705,8 +711,8 @@ int nacl_spawn_pipe(int pipefd[2]) {
   int write_fd;
   char path[100];
   sprintf(path, "/apipe/%d", id);
-  read_fd = open(path, O_RDONLY);
-  write_fd = open(path, O_WRONLY);
+  read_fd = open(path, O_RDONLY | flags);

[Pete Williamson, 2016/02/29 20:53:47]

What would happen here if flags had O_WRONLY set?  Did we mean instead to clear
the low bit?  IIRC, O_RDONLY is 0 and O_WRONLY is 1.

Maybe instead we should have (flags & ~O_WRONLY).

[bradnelson, 2016/03/03 18:04:03]

Nothing good :-)
Filtering out those two.

+  write_fd = open(path, O_WRONLY | flags);
   if (read_fd < 0 || write_fd < 0) {
     if (read_fd >= 0) {
       close(read_fd);