From: Simon Marlow <simonmar@microsoft.com>
Date: Thu, 29 Jun 2006 08:29:02 +0000 (+0000)
Subject: Use -fno-strict-aliasing for *all* C files in the runtime
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=125cad876ea4120e3c0388090f1244616f4e1e44

Use -fno-strict-aliasing for *all* C files in the runtime
as a precautionary measure.  It is definitely required for GC.c,
but it may well become necessary for other files in the future due to
our (mis-)use of the C "type system".
---

diff --git a/rts/Makefile b/rts/Makefile
index b1111a0..65c2c22 100644
--- a/rts/Makefile
+++ b/rts/Makefile
@@ -315,10 +315,15 @@ SRC_HC_OPTS += -optc-fno-stack-protector
 endif
 
 # -O3 helps unroll some loops (especially in copy() with a constant argument).
-# -fno-strict-aliasing is a hack because we often mix StgPtr and StgClosure pointers
-# to the same object, and gcc will assume these don't alias.  eg. it happens in
-# copy() with gcc 3.4.3, the upd_evacee() assigments get moved before the object copy.
-GC_HC_OPTS += -optc-O3 -optc-fno-strict-aliasing
+GC_HC_OPTS += -optc-O3
+
+# -fno-strict-aliasing is required for the runtime, because we often
+# use a variety of types to represent closure pointers (StgPtr,
+# StgClosure, StgMVar, etc.), and without -fno-strict-aliasing gcc is
+# allowed to assume that these pointers do not alias.  eg. without
+# this flag we get problems in GC.c:copy() with gcc 3.4.3, the
+# upd_evacee() assigments get moved before the object copy.
+SRC_CC_OPTS += -fno-strict-aliasing
 
 # Cmm must be compiled via-C for now, because the NCG can't handle loops
 SRC_HC_OPTS += -fvia-C