SnoopPrecompile + pipe handling

This switches to SnoopPrecompile and uses more careful handling of
pipes to ensure tasks run to completion (see comment in #343).

Project.toml

@@ -9,13 +9,15 @@ FoldingTrees = "1eca21be-9b9b-4ed8-839a-6d8ae26b1781"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 Preferences = "21216c6a-2e73-6563-6e65-726566657250"
 REPL = "3fa0cd96-eef1-5676-8a61-b3b8758bbffb"
+SnoopPrecompile = "66db9d55-30c0-4569-8b51-7e840670fc0c"
 UUIDs = "cf7118a7-6976-5b1a-9a39-7adc72f591a4"
 Unicode = "4ec0a83e-493e-50e2-b9ac-8f72acf5a8f5"
 
 [compat]
 CodeTracking = "0.5, 1"
 FoldingTrees = "1"
 Preferences = "1"
+SnoopPrecompile = "1"
 julia = "1.7"
 
 [extras]

src/Cthulhu.jl

@@ -807,13 +807,20 @@ with the option to `descend` into intermediate calls. `kwargs` are passed to [`d
 """
 ascend
 
-if ccall(:jl_generating_output, Cint, ()) == 1
-    input = Pipe()
-    Base.link_pipe!(input, reader_supports_async=true, writer_supports_async=true)
-    term = REPL.Terminals.TTYTerminal("dumb", input.out, IOBuffer(), IOBuffer())
+using SnoopPrecompile
+@precompile_setup begin
+    linked_pipe() = Base.link_pipe!(Pipe(), reader_supports_async=true, writer_supports_async=true)
+
+    input, output, err = linked_pipe(), linked_pipe(), linked_pipe()
+    term = REPL.Terminals.TTYTerminal("dumb", input.out, output.in, err.in)
     write(input.in, 'q')
-    descend(gcd, (Int, Int); terminal=term)
-    close(input)
+    @precompile_all_calls begin
+        descend(gcd, (Int, Int); terminal=term)
+        readuntil(output.out, "↩")
+    end
+    close(input.in)
+    close(output.in)
+    close(err.in)
     nothing
 end