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https://github.com/Z3Prover/z3
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Fix reference counting in the C layer of the OCaml bindings
The Z3 context and its reference counters are stored in a structure which is allocated by the C layer outside the OCaml heap, whenever a Z3 context is created. The structure and its Z3 context are disposed, once the last reference counter reaches zero. Reference counters are decremented by C-level finalizers. The OCaml representations for a Z3 context wrap only a pointer to the corresponding structure.
This commit is contained in:
martin-neuhaeusser
parent
b178420797
commit
b85516c271
2 changed files with 76 additions and 59 deletions
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@ -26,31 +26,31 @@ extern "C" {
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#define CAMLlocal6(X1,X2,X3,X4,X5,X6) \
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CAMLlocal5(X1,X2,X3,X4,X5); \
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CAMLlocal1(X6)
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CAMLlocal1(X6)
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#define CAMLlocal7(X1,X2,X3,X4,X5,X6,X7) \
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CAMLlocal5(X1,X2,X3,X4,X5); \
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CAMLlocal2(X6,X7)
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CAMLlocal2(X6,X7)
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#define CAMLlocal8(X1,X2,X3,X4,X5,X6,X7,X8) \
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CAMLlocal5(X1,X2,X3,X4,X5); \
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CAMLlocal3(X6,X7,X8)
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CAMLlocal3(X6,X7,X8)
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#define CAMLparam7(X1,X2,X3,X4,X5,X6,X7) \
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CAMLparam5(X1,X2,X3,X4,X5); \
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CAMLxparam2(X6,X7)
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CAMLxparam2(X6,X7)
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#define CAMLparam8(X1,X2,X3,X4,X5,X6,X7,X8) \
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CAMLparam5(X1,X2,X3,X4,X5); \
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CAMLxparam3(X6,X7,X8)
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CAMLxparam3(X6,X7,X8)
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#define CAMLparam9(X1,X2,X3,X4,X5,X6,X7,X8,X9) \
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CAMLparam5(X1,X2,X3,X4,X5); \
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CAMLxparam4(X6,X7,X8,X9)
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#define CAMLparam12(X1,X2,X3,X4,X5,X6,X7,X8,X9,X10,X11,X12) \
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CAMLparam5(X1,X2,X3,X4,X5); \
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CAMLxparam5(X6,X7,X8,X9,X10); \
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CAMLxparam2(X11,X12)
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CAMLxparam2(X11,X12)
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#define CAMLparam13(X1,X2,X3,X4,X5,X6,X7,X8,X9,X10,X11,X12,X13) \
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CAMLparam5(X1,X2,X3,X4,X5); \
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CAMLxparam5(X6,X7,X8,X9,X10); \
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CAMLxparam3(X11,X12,X13)
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CAMLxparam3(X11,X12,X13)
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static struct custom_operations default_custom_ops = {
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@ -68,51 +68,68 @@ static struct custom_operations default_custom_ops = {
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CAMLprim DLL_PUBLIC value n_context_of_ ## X(value v) { \
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CAMLparam1(v); \
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CAMLlocal1(result); \
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Z3_context_plus cp; \
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Z3_ ## X ## _plus * p = (Z3_ ## X ## _plus *) Data_custom_val(v); \
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cp = p->cp; \
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result = caml_alloc_custom(&Z3_context_plus_custom_ops, sizeof(Z3_context_plus), 0, 1); \
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*(Z3_context_plus*)Data_custom_val(result) = *p->cp; \
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*(Z3_context_plus*)Data_custom_val(result) = cp; \
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/* We increment the usage counter of the context */ \
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cp->obj_count++; \
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CAMLreturn(result); \
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}
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/* Context objects */
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/* The Z3context_plus_data exists exactly once for each context,
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no matter how many custom blocks for that context exist.
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Each custom block only stores a pointer to the corresponding
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Z3_context_plus_data. This ensures that the reference counting
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is performed at exactly one place and not within the custom
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blocks that get copied. */
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typedef struct {
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Z3_context ctx;
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unsigned long obj_count:sizeof(unsigned long)-1;
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unsigned ok_to_delete:1;
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} Z3_context_plus;
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unsigned long obj_count;
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} Z3_context_plus_data;
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/* A context is wrapped to an OCaml value by storing a pointer
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to its associated Z3_context_plus_data instance.
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This instance gets created in mk_context and is deleted
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together with the Z3 context instance in try_to_delete_context
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whenever the obj_count field is zero. */
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typedef Z3_context_plus_data* Z3_context_plus;
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Z3_context_plus Z3_context_plus_mk(Z3_context c) {
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Z3_context_plus r;
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r.ctx = c;
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r.obj_count = 0;
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r.ok_to_delete = 0;
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/* printf("ctx++ %p\n", c); */
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Z3_context_plus r = (Z3_context_plus)malloc(sizeof(Z3_context_plus_data));
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r->ctx = c;
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/* The context created here will be wrapped into a custom block.
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Hence, we assign it a counter of one. */
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r->obj_count = 1;
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return r;
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}
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Z3_context Z3_context_plus_raw(Z3_context_plus * cp) {
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return cp->ctx;
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return (*cp)->ctx;
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}
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void try_to_delete_context(Z3_context_plus * cp) {
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if (!cp->ok_to_delete || cp->obj_count != 0)
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/* printf("Trying to delete context %p.\n", cp->ctx) */ ;
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inline void try_to_delete_context(Z3_context_plus cp) {
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if (cp->obj_count > 0)
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/* printf("try_to_delete_context: Not deleting context %p(%p) with cnt=%lu.\n", cp, cp->ctx, cp->obj_count) */ ;
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else if (cp->obj_count < 0)
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printf("try_to_delete_context: ERROR, found context %p(%p) with negative cnt=%lu.\n", cp, cp->ctx, cp->obj_count);
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else {
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/* printf("Actually deleting context %p.\n", cp->ctx); */
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printf("try_to_delete_context: Deleting context %p(%p) with cnt=%lu.\n", cp, cp->ctx, cp->obj_count);
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Z3_del_context(cp->ctx);
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cp->ctx = 0;
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cp->ctx = NULL;
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cp->obj_count = 0;
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cp->ok_to_delete = 0;
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free(cp);
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}
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}
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void Z3_context_finalize(value v) {
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Z3_context_plus * cp = (Z3_context_plus*)Data_custom_val(v);
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/* printf("ctx--; cnt=%lu\n", cp->obj_count); */
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cp->ok_to_delete = 1;
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try_to_delete_context(cp);
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Z3_context_plus cp = *(Z3_context_plus*)Data_custom_val(v);
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cp->obj_count--;
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try_to_delete_context(cp);
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}
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static struct custom_operations Z3_context_plus_custom_ops = {
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@ -129,14 +146,14 @@ static struct custom_operations Z3_context_plus_custom_ops = {
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/* AST objects */
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typedef struct {
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Z3_context_plus * cp;
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Z3_context_plus cp;
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Z3_ast a;
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} Z3_ast_plus;
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Z3_ast_plus Z3_ast_plus_mk(Z3_context_plus * cp, Z3_ast a) {
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Z3_ast_plus Z3_ast_plus_mk(Z3_context_plus cp, Z3_ast a) {
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Z3_ast_plus r;
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r.cp = cp;
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r.a = a;
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r.a = a;
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/* printf("++\n"); */
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cp->obj_count++;
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Z3_inc_ref(cp->ctx, a);
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@ -148,7 +165,7 @@ Z3_ast Z3_ast_plus_raw(Z3_ast_plus * ap) {
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}
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void Z3_ast_finalize(value v) {
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/* printf("--\n"); */
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/* printf("--\n"); */
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Z3_ast_plus * ap = (Z3_ast_plus*)(Data_custom_val(v));
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Z3_dec_ref(ap->cp->ctx, ap->a);
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ap->cp->obj_count--;
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@ -203,11 +220,11 @@ MK_CTX_OF(ast)
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#define MK_PLUS_OBJ_NO_REF(X) \
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typedef struct { \
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Z3_context_plus * cp; \
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Z3_context_plus cp; \
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Z3_ ## X p; \
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} Z3_ ## X ## _plus; \
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\
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Z3_ ## X ## _plus Z3_ ## X ## _plus_mk(Z3_context_plus * cp, Z3_ ## X p) { \
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Z3_ ## X ## _plus Z3_ ## X ## _plus_mk(Z3_context_plus cp, Z3_ ## X p) { \
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Z3_ ## X ## _plus r; \
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r.cp = cp; \
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r.p = p; \
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@ -239,11 +256,11 @@ MK_CTX_OF(ast)
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#define MK_PLUS_OBJ(X) \
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typedef struct { \
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Z3_context_plus * cp; \
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Z3_context_plus cp; \
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Z3_ ## X p; \
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} Z3_ ## X ## _plus; \
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\
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Z3_ ## X ## _plus Z3_ ## X ## _plus_mk(Z3_context_plus * cp, Z3_ ## X p) { \
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Z3_ ## X ## _plus Z3_ ## X ## _plus_mk(Z3_context_plus cp, Z3_ ## X p) { \
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Z3_ ## X ## _plus r; \
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r.cp = cp; \
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r.p = p; \
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@ -309,7 +326,7 @@ CAMLprim DLL_PUBLIC value n_is_null(value p) {
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CAMLprim DLL_PUBLIC value n_mk_null( void ) {
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CAMLparam0();
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CAMLlocal1(result);
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CAMLlocal1(result);
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result = caml_alloc(1, 0);
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result = Val_int(0);
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CAMLreturn (result);
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