also redirect JL_STDERR etc. when redirecting to devnull

Author: IanButterworth

base/stream.jl

@@ -1244,6 +1244,14 @@ function _redirect_io_libc(stream, unix_fd::Int)
     dup(posix_fd, RawFD(unix_fd))
     nothing
 end
+function _set_cglobal_stdio(f::RedirectStdStream, handle::Union{LibuvStream, IOStream})
+    c_sym = f.unix_fd == 0 ? cglobal(:jl_uv_stdin, Ptr{Cvoid}) :
+            f.unix_fd == 1 ? cglobal(:jl_uv_stdout, Ptr{Cvoid}) :
+            f.unix_fd == 2 ? cglobal(:jl_uv_stderr, Ptr{Cvoid}) :
+            C_NULL
+    c_sym == C_NULL || unsafe_store!(c_sym, handle.handle)
+    nothing
+end
 function _redirect_io_global(io, unix_fd::Int)
     unix_fd == 0 && (global stdin = io)
     unix_fd == 1 && (global stdout = io)
@@ -1252,18 +1260,15 @@ function _redirect_io_global(io, unix_fd::Int)
 end
 function (f::RedirectStdStream)(handle::Union{LibuvStream, IOStream})
     _redirect_io_libc(handle, f.unix_fd)
-    c_sym = f.unix_fd == 0 ? cglobal(:jl_uv_stdin, Ptr{Cvoid}) :
-            f.unix_fd == 1 ? cglobal(:jl_uv_stdout, Ptr{Cvoid}) :
-            f.unix_fd == 2 ? cglobal(:jl_uv_stderr, Ptr{Cvoid}) :
-            C_NULL
-    c_sym == C_NULL || unsafe_store!(c_sym, handle.handle)
+    _set_cglobal_stdio(f, handle)
     _redirect_io_global(handle, f.unix_fd)
     return handle
 end
 function (f::RedirectStdStream)(::DevNull)
     nulldev = @static Sys.iswindows() ? "NUL" : "/dev/null"
     handle = open(nulldev, write=f.writable)
     _redirect_io_libc(handle, f.unix_fd)
+    _set_cglobal_stdio(f, handle)
     close(handle) # handle has been dup'ed in _redirect_io_libc
     _redirect_io_global(devnull, f.unix_fd)
     return devnull