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Define the behaviour of integer division by zero

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gingerBill
2025-08-08 10:00:11 +01:00
parent 3194fda8f3
commit e4a0228a80
4 changed files with 247 additions and 30 deletions
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52
src/check_expr.cpp
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@@ -129,6 +129,8 @@ gb_internal bool check_is_castable_to(CheckerContext *c, Operand *operand, Type
gb_internal bool is_exact_value_zero(ExactValue const &v);
gb_internal IntegerDivisionByZeroKind check_for_integer_division_by_zero(Ast *node);
enum LoadDirectiveResult {
LoadDirective_Success = 0,
LoadDirective_Error = 1,
@@ -4308,7 +4310,25 @@ gb_internal void check_binary_expr(CheckerContext *c, Operand *x, Ast *node, Typ
}
if (fail) {
error(y->expr, "Division by zero not allowed");
if (is_type_integer(x->type) || (x->mode == Addressing_Constant && x->value.kind == ExactValue_Integer)) {
if (check_for_integer_division_by_zero(node) == IntegerDivisionByZero_Zero) {
// Okay
break;
}
}
switch (op.kind) {
case Token_Mod:
case Token_ModMod:
case Token_ModEq:
case Token_ModModEq:
error(y->expr, "Division by zero through '%.*s' not allowed", LIT(token_strings[op.kind]));
break;
case Token_Quo:
case Token_QuoEq:
error(y->expr, "Division by zero not allowed");
break;
}
x->mode = Addressing_Invalid;
return;
}
@@ -4348,7 +4368,30 @@ gb_internal void check_binary_expr(CheckerContext *c, Operand *x, Ast *node, Typ
}
}
x->value = exact_binary_operator_value(op.kind, a, b);
match_exact_values(&a, &b);
if (check_for_integer_division_by_zero(node) == IntegerDivisionByZero_Zero &&
b.kind == ExactValue_Integer && big_int_is_zero(&b.value_integer) &&
(op.kind == Token_QuoEq || op.kind == Token_Mod || op.kind == Token_ModMod)) {
if (op.kind == Token_QuoEq) {
// x/0 == 0
x->value = b;
} else {
// x%0 == x
/*
NOTE(bill): @integer division by zero rules
truncated: r = a - b*trunc(a/b)
floored: r = a - b*floor(a/b)
IFF a/0 == 0, then (a%0 == a) or (a%%0 == a)
*/
x->value = a;
}
} else {
x->value = exact_binary_operator_value(op.kind, a, b);
}
if (is_type_typed(x->type)) {
if (node != nullptr) {
@@ -9595,6 +9638,11 @@ gb_internal bool check_for_dynamic_literals(CheckerContext *c, Ast *node, AstCom
return cl->elems.count > 0;
}
gb_internal IntegerDivisionByZeroKind check_for_integer_division_by_zero(Ast *node) {
// TODO(bill): per file `#+feature` flags
return build_context.integer_division_by_zero_behaviour;
}
gb_internal ExprKind check_compound_literal(CheckerContext *c, Operand *o, Ast *node, Type *type_hint) {
ExprKind kind = Expr_Expr;
ast_node(cl, CompoundLit, node);