CLabel: Catch #11155 during C-- pretty-printing

In #11555 we ended up generating references to the non-existence
stg_ap_0_upd. Here we add asserts to verify that we don't generate
references to non-existent selector or application symbols.

It would likely also make sense to add further asserts during code
generation, so we can catch the issue even closer to its source.

Test Plan: Validate

Reviewers: simonmar, austin, ezyang

Reviewed By: simonmar, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2230

GHC Trac Issues: #11155

1 files changed, 17 insertions, 4 deletions

diff --git a/compiler/cmm/CLabel.hs b/compiler/cmm/CLabel.hs
index bb5be5d04b..df0020301f 100644
--- a/compiler/cmm/CLabel.hs
+++ b/compiler/cmm/CLabel.hs
@@ -6,6 +6,8 @@
 --
 -----------------------------------------------------------------------------
 
+{-# LANGUAGE CPP #-}
+
 module CLabel (
         CLabel, -- abstract type
         ForeignLabelSource(..),
@@ -113,6 +115,8 @@ module CLabel (
         pprCLabel
     ) where
 
+#include "HsVersions.h"
+
 import IdInfo
 import BasicTypes
 import Packages
@@ -127,6 +131,7 @@ import FastString
 import DynFlags
 import Platform
 import UniqSet
+import Util
 import PprCore ( {- instances -} )
 
 -- -----------------------------------------------------------------------------
@@ -1062,28 +1067,36 @@ pprCLbl (CmmLabel _ str CmmPrimCall)    = ftext str
 pprCLbl (RtsLabel (RtsApFast str))   = ftext str <> text "_fast"
 
 pprCLbl (RtsLabel (RtsSelectorInfoTable upd_reqd offset))
-  = hcat [text "stg_sel_", text (show offset),
+  = sdocWithDynFlags $ \dflags ->
+    ASSERT(offset >= 0 && offset <= mAX_SPEC_SELECTEE_SIZE dflags)
+    hcat [text "stg_sel_", text (show offset),
           ptext (if upd_reqd
                  then (sLit "_upd_info")
                  else (sLit "_noupd_info"))
         ]
 
 pprCLbl (RtsLabel (RtsSelectorEntry upd_reqd offset))
-  = hcat [text "stg_sel_", text (show offset),
+  = sdocWithDynFlags $ \dflags ->
+    ASSERT(offset >= 0 && offset <= mAX_SPEC_SELECTEE_SIZE dflags)
+    hcat [text "stg_sel_", text (show offset),
                 ptext (if upd_reqd
                         then (sLit "_upd_entry")
                         else (sLit "_noupd_entry"))
         ]
 
 pprCLbl (RtsLabel (RtsApInfoTable upd_reqd arity))
-  = hcat [text "stg_ap_", text (show arity),
+  = sdocWithDynFlags $ \dflags ->
+    ASSERT(arity > 0 && arity <= mAX_SPEC_AP_SIZE dflags)
+    hcat [text "stg_ap_", text (show arity),
                 ptext (if upd_reqd
                         then (sLit "_upd_info")
                         else (sLit "_noupd_info"))
         ]
 
 pprCLbl (RtsLabel (RtsApEntry upd_reqd arity))
-  = hcat [text "stg_ap_", text (show arity),
+  = sdocWithDynFlags $ \dflags ->
+    ASSERT(arity > 0 && arity <= mAX_SPEC_AP_SIZE dflags)
+    hcat [text "stg_ap_", text (show arity),
                 ptext (if upd_reqd
                         then (sLit "_upd_entry")
                         else (sLit "_noupd_entry"))