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Limit ref counting recursion depth (#45)
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@vtereshkov
vtereshkov authored May 8, 2021
1 parent d6bb63e commit a224817
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Showing 2 changed files with 33 additions and 26 deletions.
58 changes: 32 additions & 26 deletions src/umka_vm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -461,23 +461,23 @@ static FORCE_INLINE void doBasicAssign(void *lhs, Slot rhs, TypeKind typeKind, i
}


static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, TokenKind tokKind, Error *error);
static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, TokenKind tokKind, int depth, Error *error);


static FORCE_INLINE void doChangePtrBaseRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, TokenKind tokKind, Error *error)
static FORCE_INLINE void doChangePtrBaseRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, TokenKind tokKind, int depth, Error *error)
{
if (typeKindGarbageCollected(type->base->kind))
{
void *data = ptr;
if (type->base->kind == TYPE_PTR || type->base->kind == TYPE_STR)
data = *(void **)data;

doBasicChangeRefCnt(fiber, pages, data, type->base, tokKind, error);
doBasicChangeRefCnt(fiber, pages, data, type->base, tokKind, depth + 1, error);
}
}


static FORCE_INLINE void doChangeArrayItemsRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, int len, TokenKind tokKind, Error *error)
static FORCE_INLINE void doChangeArrayItemsRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, int len, TokenKind tokKind, int depth, Error *error)
{
if (typeKindGarbageCollected(type->base->kind))
{
Expand All @@ -490,14 +490,14 @@ static FORCE_INLINE void doChangeArrayItemsRefCnt(Fiber *fiber, HeapPages *pages
if (type->base->kind == TYPE_PTR || type->base->kind == TYPE_STR)
item = *(void **)item;

doBasicChangeRefCnt(fiber, pages, item, type->base, tokKind, error);
doBasicChangeRefCnt(fiber, pages, item, type->base, tokKind, depth + 1, error);
itemPtr += itemSize;
}
}
}


static FORCE_INLINE void doChangeStructFieldsRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, TokenKind tokKind, Error *error)
static FORCE_INLINE void doChangeStructFieldsRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, TokenKind tokKind, int depth, Error *error)
{
for (int i = 0; i < type->numItems; i++)
{
Expand All @@ -507,18 +507,24 @@ static FORCE_INLINE void doChangeStructFieldsRefCnt(Fiber *fiber, HeapPages *pag
if (type->field[i]->type->kind == TYPE_PTR || type->field[i]->type->kind == TYPE_STR)
field = *(void **)field;

doBasicChangeRefCnt(fiber, pages, field, type->field[i]->type, tokKind, error);
doBasicChangeRefCnt(fiber, pages, field, type->field[i]->type, tokKind, depth + 1, error);
}
}
}


static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, TokenKind tokKind, Error *error)
static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type *type, TokenKind tokKind, int depth, Error *error)
{
// Update ref counts for pointers (including static/dynamic array items and structure/interface fields) if allocated dynamically
// Among garbage collected types, all types except the pointer and string types are represented by pointers by default
// RTTI is required for lists, trees, etc., since the propagation depth for the root ref count is unknown at compile time

if (depth > VM_MAX_REF_CNT_DEPTH)
{
printf("Warning: Data structure is too deep for garbage collection\n");
return;
}

switch (type->kind)
{
case TYPE_PTR:
Expand All @@ -544,29 +550,29 @@ static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type
{
case TYPE_ARRAY:
{
doChangeArrayItemsRefCnt(fiber, pages, chunkDataPtr, chunk->type, chunk->type->numItems, tokKind, error);
doChangeArrayItemsRefCnt(fiber, pages, chunkDataPtr, chunk->type, chunk->type->numItems, tokKind, depth, error);
break;
}
case TYPE_DYNARRAY:
{
int len = chunk->size / typeSizeNoCheck(chunk->type->base);
doChangeArrayItemsRefCnt(fiber, pages, chunkDataPtr, chunk->type, len, tokKind, error);
doChangeArrayItemsRefCnt(fiber, pages, chunkDataPtr, chunk->type, len, tokKind, depth, error);
break;
}
case TYPE_STRUCT:
{
doChangeStructFieldsRefCnt(fiber, pages, chunkDataPtr, chunk->type, tokKind, error);
doChangeStructFieldsRefCnt(fiber, pages, chunkDataPtr, chunk->type, tokKind, depth, error);
break;
}
default:
{
doChangePtrBaseRefCnt(fiber, pages, ptr, type, tokKind, error);
doChangePtrBaseRefCnt(fiber, pages, ptr, type, tokKind, depth, error);
break;
}
}
}
else
doChangePtrBaseRefCnt(fiber, pages, ptr, type, tokKind, error);
doChangePtrBaseRefCnt(fiber, pages, ptr, type, tokKind, depth, error);
}

chunkChangeRefCnt(pages, page, ptr, -1);
Expand All @@ -585,7 +591,7 @@ static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type

case TYPE_ARRAY:
{
doChangeArrayItemsRefCnt(fiber, pages, ptr, type, type->numItems, tokKind, error);
doChangeArrayItemsRefCnt(fiber, pages, ptr, type, type->numItems, tokKind, depth, error);
break;
}

Expand All @@ -602,7 +608,7 @@ static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type
// Traverse children only before removing the last remaining ref
HeapChunkHeader *chunk = pageGetChunkHeader(page, array->data);
if (chunk->refCnt == 1)
doChangeArrayItemsRefCnt(fiber, pages, array->data, type, array->len, tokKind, error);
doChangeArrayItemsRefCnt(fiber, pages, array->data, type, array->len, tokKind, depth, error);

chunkChangeRefCnt(pages, page, array->data, -1);
}
Expand All @@ -612,7 +618,7 @@ static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type

case TYPE_STRUCT:
{
doChangeStructFieldsRefCnt(fiber, pages, ptr, type, tokKind, error);
doChangeStructFieldsRefCnt(fiber, pages, ptr, type, tokKind, depth, error);
break;
}

Expand All @@ -623,7 +629,7 @@ static void doBasicChangeRefCnt(Fiber *fiber, HeapPages *pages, void *ptr, Type
Type *__selftype = *(Type **)((char *)ptr + type->field[1]->offset);

if (__self)
doBasicChangeRefCnt(fiber, pages, __self, __selftype, tokKind, error);
doBasicChangeRefCnt(fiber, pages, __self, __selftype, tokKind, depth + 1, error);
break;
}

Expand Down Expand Up @@ -942,7 +948,7 @@ static FORCE_INLINE void doBuiltinScanf(Fiber *fiber, HeapPages *pages, bool con

// Decrease old string ref count
Type destType = {.kind = TYPE_STR};
doBasicChangeRefCnt(fiber, pages, *dest, &destType, TOK_MINUSMINUS, error);
doBasicChangeRefCnt(fiber, pages, *dest, &destType, TOK_MINUSMINUS, 0, error);

// Allocate new string
*dest = chunkAlloc(pages, strlen(src) + 1, NULL, error);
Expand Down Expand Up @@ -1006,7 +1012,7 @@ static FORCE_INLINE void doBuiltinMakefromarr(Fiber *fiber, HeapPages *pages, Er
memcpy(dest->data, src, dest->len * dest->itemSize);

// Increase result items' ref counts, as if they have been assigned one by one
doChangeArrayItemsRefCnt(fiber, pages, dest->data, dest->type, dest->len, TOK_PLUSPLUS, error);
doChangeArrayItemsRefCnt(fiber, pages, dest->data, dest->type, dest->len, TOK_PLUSPLUS, 0, error);

(--fiber->top)->ptrVal = (int64_t)dest;
}
Expand Down Expand Up @@ -1049,7 +1055,7 @@ static FORCE_INLINE void doBuiltinMaketoarr(Fiber *fiber, HeapPages *pages, Erro
memcpy(dest, src->data, src->len * src->itemSize);

// Increase result items' ref counts, as if they have been assigned one by one
doChangeArrayItemsRefCnt(fiber, pages, dest, destType, destType->numItems, TOK_PLUSPLUS, error);
doChangeArrayItemsRefCnt(fiber, pages, dest, destType, destType->numItems, TOK_PLUSPLUS, 0, error);

(--fiber->top)->ptrVal = (int64_t)dest;
}
Expand Down Expand Up @@ -1107,7 +1113,7 @@ static FORCE_INLINE void doBuiltinAppend(Fiber *fiber, HeapPages *pages, Error *
memcpy((char *)result->data + array->len * array->itemSize, (char *)rhs, rhsLen * array->itemSize);

// Increase result items' ref counts, as if they have been assigned one by one
doChangeArrayItemsRefCnt(fiber, pages, result->data, result->type, result->len, TOK_PLUSPLUS, error);
doChangeArrayItemsRefCnt(fiber, pages, result->data, result->type, result->len, TOK_PLUSPLUS, 0, error);

(--fiber->top)->ptrVal = (int64_t)result;
}
Expand Down Expand Up @@ -1135,7 +1141,7 @@ static FORCE_INLINE void doBuiltinDelete(Fiber *fiber, HeapPages *pages, Error *
memcpy((char *)result->data + index * result->itemSize, (char *)array->data + (index + 1) * result->itemSize, (result->len - index) * result->itemSize);

// Increase result items' ref counts, as if they have been assigned one by one
doChangeArrayItemsRefCnt(fiber, pages, result->data, result->type, result->len, TOK_PLUSPLUS, error);
doChangeArrayItemsRefCnt(fiber, pages, result->data, result->type, result->len, TOK_PLUSPLUS, 0, error);

(--fiber->top)->ptrVal = (int64_t)result;
}
Expand Down Expand Up @@ -1198,7 +1204,7 @@ static FORCE_INLINE void doBuiltinSlice(Fiber *fiber, HeapPages *pages, Error *e
memcpy((char *)result->data, (char *)array->data + startIndex * result->itemSize, result->len * result->itemSize);

// Increase result items' ref counts, as if they have been assigned one by one
doChangeArrayItemsRefCnt(fiber, pages, result->data, result->type, result->len, TOK_PLUSPLUS, error);
doChangeArrayItemsRefCnt(fiber, pages, result->data, result->type, result->len, TOK_PLUSPLUS, 0, error);

(--fiber->top)->ptrVal = (int64_t)result;
}
Expand Down Expand Up @@ -1436,7 +1442,7 @@ static FORCE_INLINE void doChangeRefCnt(Fiber *fiber, HeapPages *pages, Error *e
TokenKind tokKind = fiber->code[fiber->ip].tokKind;
Type *type = (Type *)fiber->code[fiber->ip].operand.ptrVal;

doBasicChangeRefCnt(fiber, pages, ptr, type, tokKind, error);
doBasicChangeRefCnt(fiber, pages, ptr, type, tokKind, 0, error);

if (fiber->code[fiber->ip].inlineOpcode == OP_POP)
fiber->top++;
Expand All @@ -1455,12 +1461,12 @@ static FORCE_INLINE void doChangeRefCntAssign(Fiber *fiber, HeapPages *pages, Er
Type *type = (Type *)fiber->code[fiber->ip].operand.ptrVal;

// Increase right-hand side ref count
doBasicChangeRefCnt(fiber, pages, (void *)rhs.ptrVal, type, TOK_PLUSPLUS, error);
doBasicChangeRefCnt(fiber, pages, (void *)rhs.ptrVal, type, TOK_PLUSPLUS, 0, error);

// Decrease left-hand side ref count
Slot lhsDeref = {.ptrVal = (int64_t)lhs};
doBasicDeref(&lhsDeref, type->kind, error);
doBasicChangeRefCnt(fiber, pages, (void *)lhsDeref.ptrVal, type, TOK_MINUSMINUS, error);
doBasicChangeRefCnt(fiber, pages, (void *)lhsDeref.ptrVal, type, TOK_MINUSMINUS, 0, error);

doBasicAssign(lhs, rhs, type->kind, typeSizeNoCheck(type), error);
fiber->ip++;
Expand Down
1 change: 1 addition & 0 deletions src/umka_vm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ enum
VM_MIN_FREE_STACK = 1024, // Slots
VM_MIN_HEAP_CHUNK = 64, // Bytes
VM_MIN_HEAP_PAGE = 1024 * 1024, // Bytes
VM_MAX_REF_CNT_DEPTH = 5000,

VM_HEAP_CHUNK_MAGIC = 0x1234567887654321LL,

Expand Down

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