diff -rc aterm-1142707243.10633/aterm/aterm.c aterm/aterm/aterm.c
*** aterm-1142707243.10633/aterm/aterm.c 2006-02-08 11:35:28.000000000 +0100
--- aterm/aterm/aterm.c 2006-04-25 17:10:52.000000000 +0200
***************
*** 193,198 ****
--- 193,199 ----
/* that have char == 2 bytes, and sizeof(header_type) == 2 */
assert(sizeof(header_type) == sizeof(ATerm *));
assert(sizeof(header_type) >= 4);
+ assert(sizeof(ATerm) == sizeof(MachineWord));
/*}}} */
/*{{{ Initialize buffer */
diff -rc aterm-1142707243.10633/aterm/memory.c aterm/aterm/memory.c
*** aterm-1142707243.10633/aterm/memory.c 2006-03-09 15:02:56.000000000 +0100
--- aterm/aterm/memory.c 2006-04-25 18:22:00.000000000 +0200
***************
*** 119,130 ****
hash_number(tmp,3))
*/
#define HASHNUMBER3(t)\
! FINISH(COMBINE(START(((MachineWord*)t)[0]), ((MachineWord*)t)[2]))
#define HASHNUMBER4(t)\
! FINISH(COMBINE(COMBINE(START(((MachineWord*)t)[0]), \
! ((MachineWord*)t)[2]),((MachineWord*)t)[3]))
#define HASHINT(val) \
FINISH(COMBINE(START( (AT_INT<<SHIFT_TYPE) ), val))
--- 119,171 ----
hash_number(tmp,3))
*/
+ /* The ATerm library use some heavy aliasing. For instance, the
+ various ATermXXX structures are referenced through MachineWord
+ arrays. This is not generally allowed by the C standard --- see
+ C99, section 6.5, clause 7. In particular, this means that you
+ cannot assign something through an ATermXXX pointer, e.g.,
+
+ protoAppl->header = header;
+
+ and then read it through a MachineWord*, e.g.,
+
+ hnr = hash_number((ATerm) protoAppl, 2);
+
+ (hash_number walks over the term by casting it to a MachineWord*).
+
+ However, the same clause of the C standard also specifies that you
+ *can* read the memory location through a union type that contains
+ both the original type (e.g. ATermAppl) and the type used to read
+ the memory location (e.g. MachineWord). That's what we do
+ below: we have a union of all the types that occur in the various
+ ATerm types. We then read the "w" element of the union. The
+ compiler is not allowed to assume absence of aliasing with the
+ other types in the union.
+
+ A better solution would be to hash the term through a character
+ pointer (since *any* memory location can be legally read as a
+ character), but I'm too lazy right now. Performance might also
+ suffer if we do that. */
+
+ typedef union
+ {
+ MachineWord w;
+ header_type header;
+ ATerm term;
+ ATermList list;
+ int i;
+ double d;
+ void* p;
+ } Aliaser;
+
+ #define GET_WORD(t, n) (((Aliaser*) (((MachineWord*) t) + n))->w)
+
#define HASHNUMBER3(t)\
! FINISH(COMBINE(START(GET_WORD(t, 0)), GET_WORD(t, 2)))
#define HASHNUMBER4(t)\
! FINISH(COMBINE(COMBINE(START(GET_WORD(t, 0)), \
! GET_WORD(t, 2)), GET_WORD(t, 3)))
#define HASHINT(val) \
FINISH(COMBINE(START( (AT_INT<<SHIFT_TYPE) ), val))
***************
*** 132,144 ****
#endif /* HASHPEM */
! #define PROTO_APPL_ARGS ((ATerm *) (protoTerm + ARG_OFFSET))
#define SET_PROTO_APPL_ARG(i, a) \
! (PROTO_APPL_ARGS[(i)] = (a))
#define GET_PROTO_APPL_ARG(i) \
! (PROTO_APPL_ARGS[(i)])
#define CHECK_TERM(t) \
assert((t) != NULL \
--- 173,185 ----
#endif /* HASHPEM */
! #define PROTO_APPL_ARGS (protoTerm + ARG_OFFSET)
#define SET_PROTO_APPL_ARG(i, a) \
! (PROTO_APPL_ARGS[(i)] = (MachineWord) (a))
#define GET_PROTO_APPL_ARG(i) \
! ((ATerm) PROTO_APPL_ARGS[(i)])
#define CHECK_TERM(t) \
assert((t) != NULL \
***************
*** 323,336 ****
#else
static HashNumber hash_number(ATerm t, int size)
{
- MachineWord *words = (MachineWord *) t;
int i;
HashNumber hnr;
! hnr = START(HIDE_AGE_MARK(words[0]));
for (i=2; i<size; i++) {
! hnr = COMBINE(hnr, words[i]);
}
return FINISH(hnr);
--- 364,376 ----
#else
static HashNumber hash_number(ATerm t, int size)
{
int i;
HashNumber hnr;
! hnr = START(HIDE_AGE_MARK(GET_WORD(t, 0)));
for (i=2; i<size; i++) {
! hnr = COMBINE(hnr, GET_WORD(t, i));
}
return FINISH(hnr);
***************
*** 338,351 ****
static HashNumber hash_number_anno(ATerm t, int size, ATerm anno)
{
- MachineWord *words = (MachineWord *) t;
int i;
HashNumber hnr;
! hnr = START(HIDE_AGE_MARK(words[0]));
for (i=2; i<size; i++) {
! hnr = COMBINE(hnr, words[i]);
}
hnr = COMBINE(hnr, (MachineWord)anno);
--- 378,390 ----
static HashNumber hash_number_anno(ATerm t, int size, ATerm anno)
{
int i;
HashNumber hnr;
! hnr = START(HIDE_AGE_MARK(GET_WORD(t, 0)));
for (i=2; i<size; i++) {
! hnr = COMBINE(hnr, GET_WORD(t, i));
}
hnr = COMBINE(hnr, (MachineWord)anno);
***************
*** 1639,1645 ****
protoAppl->header = header;
CHECK_HEADER(protoAppl->header);
! if (args != PROTO_APPL_ARGS) {
for (i=0; i<arity; i++) {
CHECK_TERM(args[i]);
SET_PROTO_APPL_ARG(i, args[i]);
--- 1678,1684 ----
protoAppl->header = header;
CHECK_HEADER(protoAppl->header);
! if (args != (ATerm *) PROTO_APPL_ARGS) {
for (i=0; i<arity; i++) {
CHECK_TERM(args[i]);
SET_PROTO_APPL_ARG(i, args[i]);
***************
*** 1680,1686 ****
hashtable[hnr] = cur;
}
! if (args != PROTO_APPL_ARGS) {
for (i=0; i<arity; i++) {
protected_buffer[i] = NULL;
}
--- 1719,1725 ----
hashtable[hnr] = cur;
}
! if (args != (ATerm *) PROTO_APPL_ARGS) {
for (i=0; i<arity; i++) {
protected_buffer[i] = NULL;
}
***************
*** 2144,2150 ****
}
SET_PROTO_APPL_ARG(n, arg);
! result = ATmakeApplArray(sym, PROTO_APPL_ARGS);
annos = AT_getAnnotations((ATerm)appl);
if (annos != NULL) {
result = (ATermAppl)AT_setAnnotations((ATerm)result, annos);
--- 2183,2189 ----
}
SET_PROTO_APPL_ARG(n, arg);
! result = ATmakeApplArray(sym, (ATerm *) PROTO_APPL_ARGS);
annos = AT_getAnnotations((ATerm)appl);
if (annos != NULL) {
result = (ATermAppl)AT_setAnnotations((ATerm)result, annos);
