ExprNode* ReadExpr (FILE* F, ObjData* O)
/* Read an expression from the given file */
{
ExprNode* Expr;
/* Read the node tag and handle NULL nodes */
unsigned char Op = Read8 (F);
if (Op == EXPR_NULL) {
return 0;
}
/* Create a new node */
Expr = NewExprNode (O, Op);
/* Check the tag and handle the different expression types */
if (EXPR_IS_LEAF (Op)) {
switch (Op) {
case EXPR_LITERAL:
Expr->V.IVal = Read32Signed (F);
break;
case EXPR_SYMBOL:
/* Read the import number */
Expr->V.ImpNum = ReadVar (F);
break;
case EXPR_SECTION:
/* Read the section number */
Expr->V.SecNum = ReadVar (F);
break;
default:
Error ("Invalid expression op: %02X", Op);
}
} else {
/* Not a leaf node */
Expr->Left = ReadExpr (F, O);
Expr->Right = ReadExpr (F, O);
}
/* Return the tree */
return Expr;
}
static void SkipExpr (FILE* F)
/* Skip an expression from the given file */
{
/* Read the node tag and handle NULL nodes */
unsigned char Op = Read8 (F);
if (Op == EXPR_NULL) {
return;
}
/* Check the tag and handle the different expression types */
if (EXPR_IS_LEAF (Op)) {
switch (Op) {
case EXPR_LITERAL:
(void) Read32Signed (F);
break;
case EXPR_SYMBOL:
/* Read the import number */
(void) ReadVar (F);
break;
case EXPR_SECTION:
case EXPR_BANK:
/* Read the segment number */
(void) ReadVar (F);
break;
default:
Error ("Invalid expression op: %02X", Op);
}
} else {
/* Not a leaf node */
SkipExpr (F);
SkipExpr (F);
}
}
int IsConstExpr (ExprNode* Root)
/* Return true if the given expression is a constant expression, that is, one
* with no references to external symbols.
*/
{
int Const;
Export* E;
Section* S;
MemoryArea* M;
if (EXPR_IS_LEAF (Root->Op)) {
switch (Root->Op) {
case EXPR_LITERAL:
return 1;
case EXPR_SYMBOL:
/* Get the referenced export */
E = GetExprExport (Root);
/* If this export has a mark set, we've already encountered it.
* This means that the export is used to define it's own value,
* which in turn means, that we have a circular reference.
*/
if (ExportHasMark (E)) {
CircularRefError (E);
Const = 0;
} else {
MarkExport (E);
Const = IsConstExport (E);
UnmarkExport (E);
}
return Const;
case EXPR_SECTION:
/* A section expression is const if the segment it is in is
* not relocatable and already placed.
*/
S = GetExprSection (Root);
M = S->Seg->MemArea;
return M != 0 && (M->Flags & MF_PLACED) != 0 && !M->Relocatable;
case EXPR_SEGMENT:
/* A segment is const if it is not relocatable and placed */
M = Root->V.Seg->MemArea;
return M != 0 && (M->Flags & MF_PLACED) != 0 && !M->Relocatable;
case EXPR_MEMAREA:
/* A memory area is const if it is not relocatable and placed */
return !Root->V.Mem->Relocatable &&
(Root->V.Mem->Flags & MF_PLACED);
default:
/* Anything else is not const */
return 0;
}
} else if (EXPR_IS_UNARY (Root->Op)) {
SegExprDesc D;
/* Special handling for the BANK pseudo function */
switch (Root->Op) {
case EXPR_BANK:
/* Get segment references for the expression */
GetSegExprVal (Root->Left, &D);
/* The expression is const if the expression contains exactly
* one segment that is assigned to a memory area which has a
* bank attribute that is constant.
*/
return (D.TooComplex == 0 &&
D.Seg != 0 &&
D.Seg->MemArea != 0 &&
D.Seg->MemArea->BankExpr != 0 &&
IsConstExpr (D.Seg->MemArea->BankExpr));
default:
/* All others handled normal */
return IsConstExpr (Root->Left);
}
} else {
/* We must handle shortcut boolean expressions here */
switch (Root->Op) {
case EXPR_BOOLAND:
if (IsConstExpr (Root->Left)) {
/* lhs is const, if it is zero, don't eval right */
if (GetExprVal (Root->Left) == 0) {
return 1;
} else {
return IsConstExpr (Root->Right);
}
} else {
/* lhs not const --> tree not const */
return 0;
}
break;
case EXPR_BOOLOR:
if (IsConstExpr (Root->Left)) {
/* lhs is const, if it is not zero, don't eval right */
if (GetExprVal (Root->Left) != 0) {
return 1;
} else {
return IsConstExpr (Root->Right);
}
} else {
/* lhs not const --> tree not const */
return 0;
}
break;
default:
/* All others are handled normal */
return IsConstExpr (Root->Left) && IsConstExpr (Root->Right);
}
}
}
