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.

5 files changed, 23 insertions, 14 deletions

diff --git a/global.c b/global.c
index 0a938f2..5685186 100644
--- a/global.c
+++ b/global.c
@@ -48,6 +48,7 @@ const_string_t UserPrefix = "";
 const_string_t ServerDemux = strNULL;
 const_string_t SubrPrefix = "";
 const_string_t RoutinePrefix = "";
+const_string_t OOLPostfix = "P";
 
 string_t yyinname;
 
diff --git a/global.h b/global.h
index ca4d865..8dbb6fd 100644
--- a/global.h
+++ b/global.h
@@ -53,6 +53,7 @@ extern const_string_t UserPrefix;
 extern const_string_t ServerDemux;
 extern const_string_t SubrPrefix;
 extern const_string_t RoutinePrefix;
+extern const_string_t OOLPostfix;
 
 extern int yylineno;
 extern string_t yyinname;
diff --git a/server.c b/server.c
index 56ccfc7..15fc128 100644
--- a/server.c
+++ b/server.c
@@ -777,9 +777,9 @@ WriteServerCallArg(FILE *file, const argument_t *arg)
 		    arg->argTTName,
 		    arg->argLongForm ? ".msgtl_header" : "");
 	    fprintf(file, "? %s ", InArgMsgField(arg));
-	    fprintf(file, ": *((%s **)%s)",
-			FetchServerType(arg->argType->itElement),
-			InArgMsgField(arg));
+	    fprintf(file, ": %s%s",
+		    InArgMsgField(arg),
+		    OOLPostfix);
 	}
 	else
 	    fprintf(file, "%s", InArgMsgField(arg));
@@ -816,8 +816,8 @@ WriteDestroyArg(FILE *file, const argument_t *arg)
 		arg->argRequestPos,
 		arg->argTTName,
 		arg->argLongForm ? ".msgtl_header" : "");
-	fprintf(file, "\t\t\t%smig_deallocate(* (vm_offset_t *) %s, ",
-		SubrPrefix, InArgMsgField(arg));
+	fprintf(file, "\t\t\t%smig_deallocate((vm_offset_t) %s%s, ",
+		SubrPrefix, InArgMsgField(arg), OOLPostfix);
 	if (multiplier > 1)
 	    fprintf(file, "%d * ", multiplier);
 	fprintf(file, " %s);\n", InArgMsgField(count));
@@ -978,9 +978,9 @@ WritePackArgValue(FILE *file, const argument_t *arg)
 			    arg->argTTName,
 			    arg->argLongForm ? ".msgtl_header" : "",
 			    arg->argDealloc->argVarName);
-		fprintf(file, "\t\t*((%s **)OutP->%s) = %sP;\n",
-			FetchServerType(btype),
+		fprintf(file, "\t\tOutP->%s%s = %sP;\n",
 			arg->argMsgField,
+			OOLPostfix,
 			arg->argVarName);
 		if (!arg->argRoutine->rtSimpleFixedReply)
 		    fprintf(file, "\t\tmsgh_simple = FALSE;\n");
@@ -1203,9 +1203,9 @@ WritePackArg(FILE *file, const argument_t *arg)
 			arg->argTTName,
 			arg->argLongForm ? ".msgtl_header" : "",
 			arg->argDealloc->argVarName);
-	    fprintf(file, "\t\t*((%s **)OutP->%s) = %sP;\n",
-			FetchServerType(it->itElement),
+	    fprintf(file, "\t\tOutP->%s%s = %sP;\n",
 			arg->argMsgField,
+			OOLPostfix,
 			arg->argVarName);
 	    if (!arg->argRoutine->rtSimpleFixedReply)
 		fprintf(file, "\t\tmsgh_simple = FALSE;\n");
diff --git a/user.c b/user.c
index 5451a03..1f3ba3d 100644
--- a/user.c
+++ b/user.c
@@ -447,9 +447,9 @@ WritePackArgValue(FILE *file, const argument_t *arg)
 			    arg->argLongForm ? ".msgtl_header" : "",
 			    arg->argDealloc->argByReferenceUser ? "*" : "",
 			    arg->argDealloc->argVarName);
-		fprintf(file, "\t\t*((%s **)InP->%s) = %s%s;\n",
-			FetchUserType(btype),
+		fprintf(file, "\t\tInP->%s%s = %s%s;\n",
 			arg->argMsgField,
+			OOLPostfix,
 			ref, arg->argVarName);
 		if (!arg->argRoutine->rtSimpleFixedRequest)
 		    fprintf(file, "\t\tmsgh_simple = FALSE;\n");
@@ -951,9 +951,10 @@ WriteExtractArgValue(FILE *file, const argument_t *arg)
 	    fprintf(file, "\tif (!OutP->%s%s.msgt_inline)\n",
 		    arg->argTTName,
 		    arg->argLongForm ? ".msgtl_header" : "");
-	    fprintf(file, "\t    %s%s = *((%s **)OutP->%s);\n",
+	    fprintf(file, "\t    %s%s = OutP->%s%s;\n",
 		    ref, arg->argVarName,
-		    FetchUserType(btype), arg->argMsgField);
+		    arg->argMsgField,
+		    OOLPostfix);
 	    fprintf(file, "\telse if (OutP->%s", count->argMsgField);
 	    if (btype->itNumber > 1)
 		fprintf(file, " / %d", btype->itNumber);
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);