[commit: ghc] master: Comment improvements on interpreter breakpoint IO action (50972d6)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/50972d6f7c53d32d324eb5ca96d0a3f8794bdb38/ghc

>---------------------------------------------------------------

commit 50972d6f7c53d32d324eb5ca96d0a3f8794bdb38
Author: Ömer Sinan Ağacan <omeragacan at gmail.com>
Date:   Tue Mar 13 15:25:53 2018 +0300

    Comment improvements on interpreter breakpoint IO action
    
    [skip ci]


>---------------------------------------------------------------

50972d6f7c53d32d324eb5ca96d0a3f8794bdb38
 libraries/ghci/GHCi/Run.hs |  7 ++++++-
 rts/Interpreter.c          | 10 +++++-----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/libraries/ghci/GHCi/Run.hs b/libraries/ghci/GHCi/Run.hs
index d058775..2988ec2 100644
--- a/libraries/ghci/GHCi/Run.hs
+++ b/libraries/ghci/GHCi/Run.hs
@@ -298,7 +298,12 @@ setStepFlag = poke stepFlag 1
 resetStepFlag :: IO ()
 resetStepFlag = poke stepFlag 0
 
-type BreakpointCallback = Int# -> Int# -> Bool -> HValue -> IO ()
+type BreakpointCallback
+     = Int#    -- the breakpoint index
+    -> Int#    -- the module uniq
+    -> Bool    -- exception?
+    -> HValue  -- the AP_STACK, or exception
+    -> IO ()
 
 foreign import ccall "&rts_breakpoint_io_action"
    breakPointIOAction :: Ptr (StablePtr BreakpointCallback)
diff --git a/rts/Interpreter.c b/rts/Interpreter.c
index 0e80593..9eb6560 100644
--- a/rts/Interpreter.c
+++ b/rts/Interpreter.c
@@ -289,7 +289,7 @@ static StgWord app_ptrs_itbl[] = {
 };
 
 HsStablePtr rts_breakpoint_io_action; // points to the IO action which is executed on a breakpoint
-                                // it is set in main/GHC.hs:runStmt
+                                      // it is set in main/GHC.hs:runStmt
 
 Capability *
 interpretBCO (Capability* cap)
@@ -1098,10 +1098,10 @@ run_BCO:
                   // Arrange the stack to call the breakpoint IO action, and
                   // continue execution of this BCO when the IO action returns.
                   //
-                  // ioAction :: Bool        -- exception?
+                  // ioAction :: Int#        -- the breakpoint index
+                  //          -> Int#        -- the module uniq
+                  //          -> Bool        -- exception?
                   //          -> HValue      -- the AP_STACK, or exception
-                  //          -> Int         -- the breakpoint index (arg2)
-                  //          -> Int         -- the module uniq (arg3)
                   //          -> IO ()
                   //
                   ioAction = (StgClosure *) deRefStablePtr (
@@ -1111,7 +1111,7 @@ run_BCO:
                   SpW(10) = (W_)obj;
                   SpW(9)  = (W_)&stg_apply_interp_info;
                   SpW(8)  = (W_)new_aps;
-                  SpW(7)  = (W_)False_closure;         // True <=> a breakpoint
+                  SpW(7)  = (W_)False_closure;         // True <=> an exception
                   SpW(6)  = (W_)&stg_ap_ppv_info;
                   SpW(5)  = (W_)BCO_LIT(arg3_module_uniq);
                   SpW(4)  = (W_)&stg_ap_n_info;