Suppressing strict aliasing warning about machine context registers, and adding note about dubious safety.

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 Change: 179397
 ServerID: perforce.ravenbrook.com

1 files changed, 12 insertions, 12 deletions

diff --git a/mps/code/prmci3li.c b/mps/code/prmci3li.c
index 9c606f181ab..33be380ba61 100644
--- a/mps/code/prmci3li.c
+++ b/mps/code/prmci3li.c
@@ -36,26 +36,26 @@ SRCID(prmci3li, "$Id$");
 
 MRef Prmci3AddressHoldingReg(MutatorFaultContext mfc, unsigned int regnum)
 {
-  Word *gregs;
-
   AVER(regnum <= 7);
   AVER(regnum >= 0);
 
-  gregs = (Word *)&mfc->ucontext->uc_mcontext.gregs;
-
   /* .source.i486 */
   /* .assume.regref */
   /* The REG_EAX etc. symbols are only present if _GNU_SOURCE is defined.
      Currently this is in lii3gc.gmk in PFMDEFS. */
+  /* TODO: The current arrangement of the fix operation (taking a Ref *)
+     forces us to pun these registers (actually `int` on LII3GC).  We can
+     suppress the warning my casting through `char *` and this might make
+     it safe, but does it really?  RB 2012-09-10 */
   switch (regnum) {
-    case 0: return &gregs[REG_EAX];
-    case 1: return &gregs[REG_ECX];
-    case 2: return &gregs[REG_EDX];
-    case 3: return &gregs[REG_EBX];
-    case 4: return &gregs[REG_ESP];
-    case 5: return &gregs[REG_EBP];
-    case 6: return &gregs[REG_ESI];
-    case 7: return &gregs[REG_EDI];
+    case 0: return (MRef)((char *)&mfc->ucontext->uc_mcontext.gregs[REG_EAX]);
+    case 1: return (MRef)((char *)&mfc->ucontext->uc_mcontext.gregs[REG_ECX]);
+    case 2: return (MRef)((char *)&mfc->ucontext->uc_mcontext.gregs[REG_EDX]);
+    case 3: return (MRef)((char *)&mfc->ucontext->uc_mcontext.gregs[REG_EBX]);
+    case 4: return (MRef)((char *)&mfc->ucontext->uc_mcontext.gregs[REG_ESP]);
+    case 5: return (MRef)((char *)&mfc->ucontext->uc_mcontext.gregs[REG_EBP]);
+    case 6: return (MRef)((char *)&mfc->ucontext->uc_mcontext.gregs[REG_ESI]);
+    case 7: return (MRef)((char *)&mfc->ucontext->uc_mcontext.gregs[REG_EDI]);
   }
   NOTREACHED;
   return (MRef)NULL;  /* Avoids compiler warning. */