From 44753cf5a30b9324d2c4ac9021843674bde5cc3c Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Sun, 15 Feb 2015 13:29:30 +0100
Subject: Do not generate code dereferencing type-punned pointers

For variable-length arrays, up to 2048 bytes are transmitted inline.
If the array is larger, the data is transmitted out-of-line, and a
pointer to a vm_allocated region is stored at the beginning of the
array.

Previously, the generated code casted the field.  Use a union instead.

This fixes the gcc warning `dereferencing type-punned pointer will
break strict-aliasing rules [-Wstrict-aliasing]'.

* global.c (OOLPostfix): New variable.
* global.h (OOLPostfix): New declaration.
* server.c (WriteServerCallArg): Avoid cast.
(WriteDestroyArg): Likewise.
(WritePackArgValue): Likewise.
(WritePackArg): Likewise.
* user.c (WriteExtractArgValue): Likewise.
* utils.c (WriteFieldDeclPrim): Generate a union with an additional
pointer field for variable-length arrays.
---
 utils.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'utils.c')

diff --git a/utils.c b/utils.c
index 396e743..4c2a87b 100644
--- a/utils.c
+++ b/utils.c
@@ -239,10 +239,16 @@ WriteFieldDeclPrim(FILE *file, const argument_t *arg,
 	 *	use the element type and maximum size specified.
 	 *	Note arg->argCount->argMultiplier == btype->itNumber.
 	 */
-	fprintf(file, "\t\t%s %s[%d];",
+	fprintf(file, "\t\tunion {\n");
+	fprintf(file, "\t\t\t%s %s[%d];\n",
 			(*tfunc)(btype),
 			arg->argMsgField,
 			it->itNumber/btype->itNumber);
+	fprintf(file, "\t\t\t%s *%s%s;\n",
+			(*tfunc)(btype),
+			arg->argMsgField,
+			OOLPostfix);
+	fprintf(file, "\t\t};");
     }
     else
 	fprintf(file, "\t\t%s %s;", (*tfunc)(it), arg->argMsgField);
-- 
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