From: sof <unknown>
Date: Mon, 24 Aug 1998 10:47:52 +0000 (+0000)
Subject: [project @ 1998-08-24 10:47:52 by sof]
X-Git-Tag: Approx_2487_patches~297
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=8f9cbd2df7bdcbd7a91cdd80246f52dd3a80176a;p=ghc-hetmet.git

[project @ 1998-08-24 10:47:52 by sof]
Added seqZh comment on why it shouldn't be used on partially applied values
---

diff --git a/ghc/includes/StgMacros.lh b/ghc/includes/StgMacros.lh
index d498a01..3d112b3 100644
--- a/ghc/includes/StgMacros.lh
+++ b/ghc/includes/StgMacros.lh
@@ -2249,6 +2249,13 @@ extern I_ required_thread_count;
 
 The following seq# code should only be used in unoptimized code.
 Be warned: it's a potential bug-farm.
+[SOF 8/98: 
+  Yes, it completely fails to work for function values, since a PAP 
+  closure will be constructed when the arg satisfaction check fails.
+  This PAP closure will add the magic values that gets pushed on the B stack 
+  before entering the 'seqee' (new word!), as Jim is just about to tell
+  us about. Let's hear what he's got to say:
+]
 
 First we push two words on the B stack: the current value of RetReg 
 (which may or may not be live), and a continuation snatched largely out
@@ -2259,6 +2266,11 @@ polymorphic seq return point, the two words are popped off the B stack,
 RetReg is restored, and we jump to the continuation, completing the
 primop and going on our merry way.
 
+[ To workaround the shortcoming of not being able to deal with partially
+  applied values, we explicitly prohibit this at the Haskell source level
+  (i.e., we don't define an Eval instance for (->) ). 
+]
+
 \begin{code}
 
 ED_RO_(vtbl_seq);