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add runtime debug safety for dividing integer min value by -1

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closes #260
This commit is contained in:
Andrew Kelley 2017-02-14 01:08:30 -05:00
parent 0931b85bd0
commit 63d37b7cff
4 changed files with 39 additions and 7 deletions
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2
src/analyze.cpp
View File

@ -3447,7 +3447,7 @@ static int64_t max_signed_val(TypeTableEntry *type_entry) {
}
}
static int64_t min_signed_val(TypeTableEntry *type_entry) {
int64_t min_signed_val(TypeTableEntry *type_entry) {
assert(type_entry->id == TypeTableEntryIdInt);
if (type_entry->data.integral.bit_count == 64) {
return INT64_MIN;

1
src/analyze.hpp
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@ -81,6 +81,7 @@ void complete_enum(CodeGen *g, TypeTableEntry *enum_type);
bool ir_get_var_is_comptime(VariableTableEntry *var);
bool const_values_equal(ConstExprValue *a, ConstExprValue *b);
void eval_min_max_value(CodeGen *g, TypeTableEntry *type_entry, ConstExprValue *const_val, bool is_max);
int64_t min_signed_val(TypeTableEntry *type_entry);
void render_const_value(Buf *buf, ConstExprValue *const_val);
void define_local_param_variables(CodeGen *g, FnTableEntry *fn_table_entry, VariableTableEntry **arg_vars);

26
src/codegen.cpp
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@ -846,14 +846,30 @@ static LLVMValueRef gen_div(CodeGen *g, bool want_debug_safety, LLVMValueRef val
} else {
zig_unreachable();
}
LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivZeroOk");
LLVMBasicBlockRef fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivZeroFail");
LLVMBuildCondBr(g->builder, is_zero_bit, fail_block, ok_block);
LLVMBasicBlockRef div_zero_ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivZeroOk");
LLVMBasicBlockRef div_zero_fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivZeroFail");
LLVMBuildCondBr(g->builder, is_zero_bit, div_zero_fail_block, div_zero_ok_block);
LLVMPositionBuilderAtEnd(g->builder, fail_block);
LLVMPositionBuilderAtEnd(g->builder, div_zero_fail_block);
gen_debug_safety_crash(g, PanicMsgIdDivisionByZero);
LLVMPositionBuilderAtEnd(g->builder, ok_block);
LLVMPositionBuilderAtEnd(g->builder, div_zero_ok_block);
if (type_entry->id == TypeTableEntryIdInt && type_entry->data.integral.is_signed) {
LLVMValueRef neg_1_value = LLVMConstInt(type_entry->type_ref, -1, true);
LLVMValueRef int_min_value = LLVMConstInt(type_entry->type_ref, min_signed_val(type_entry), true);
LLVMBasicBlockRef overflow_ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivOverflowOk");
LLVMBasicBlockRef overflow_fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "DivOverflowFail");
LLVMValueRef num_is_int_min = LLVMBuildICmp(g->builder, LLVMIntEQ, val1, int_min_value, "");
LLVMValueRef den_is_neg_1 = LLVMBuildICmp(g->builder, LLVMIntEQ, val2, neg_1_value, "");
LLVMValueRef overflow_fail_bit = LLVMBuildAnd(g->builder, num_is_int_min, den_is_neg_1, "");
LLVMBuildCondBr(g->builder, overflow_fail_bit, overflow_fail_block, overflow_ok_block);
LLVMPositionBuilderAtEnd(g->builder, overflow_fail_block);
gen_debug_safety_crash(g, PanicMsgIdIntegerOverflow);
LLVMPositionBuilderAtEnd(g->builder, overflow_ok_block);
}
}
if (type_entry->id == TypeTableEntryIdFloat) {

17
test/run_tests.cpp
View File

@ -1700,13 +1700,28 @@ pub fn panic(message: []const u8) -> unreachable {
error Whatever;
pub fn main(args: [][]u8) -> %void {
const x = neg(-32768);
if (x == 0) return error.Whatever;
if (x == 32767) return error.Whatever;
}
fn neg(a: i16) -> i16 {
-a
}
)SOURCE");
add_debug_safety_case("signed integer division overflow", R"SOURCE(
pub fn panic(message: []const u8) -> unreachable {
@breakpoint();
while (true) {}
}
error Whatever;
pub fn main(args: [][]u8) -> %void {
const x = div(-32768, -1);
if (x == 32767) return error.Whatever;
}
fn div(a: i16, b: i16) -> i16 {
a / b
}
)SOURCE");
add_debug_safety_case("signed shift left overflow", R"SOURCE(
pub fn panic(message: []const u8) -> unreachable {
@breakpoint();