[commit: ghc] master: Document putSymbolTable determinism (2046297)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/2046297ec03bdcd4901f69cd6ae03e84dc974683/ghc

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commit 2046297ec03bdcd4901f69cd6ae03e84dc974683
Author: Bartosz Nitka <niteria at gmail.com>
Date:   Fri Jun 3 09:11:50 2016 -0700

    Document putSymbolTable determinism
    
    Like explained in the comment it's OK here.
    
    Test Plan: ./validate
    
    Reviewers: bgamari, austin, simonmar
    
    Reviewed By: simonmar
    
    Subscribers: thomie
    
    Differential Revision: https://phabricator.haskell.org/D2298
    
    GHC Trac Issues: #4012


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2046297ec03bdcd4901f69cd6ae03e84dc974683
 compiler/iface/BinIface.hs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/compiler/iface/BinIface.hs b/compiler/iface/BinIface.hs
index 0b70e8c..4290704 100644
--- a/compiler/iface/BinIface.hs
+++ b/compiler/iface/BinIface.hs
@@ -254,7 +254,9 @@ binaryInterfaceMagic dflags
 putSymbolTable :: BinHandle -> Int -> UniqFM (Int,Name) -> IO ()
 putSymbolTable bh next_off symtab = do
     put_ bh next_off
-    let names = elems (array (0,next_off-1) (eltsUFM symtab))
+    let names = elems (array (0,next_off-1) (nonDetEltsUFM symtab))
+      -- It's OK to use nonDetEltsUFM here because the elements have
+      -- indices that array uses to create order
     mapM_ (\n -> serialiseName bh n symtab) names
 
 getSymbolTable :: BinHandle -> NameCacheUpdater -> IO SymbolTable