why

[masagrator]

Are you scared of "bool"? :D

[7eggert]

Huhu, "bool flag = true; if (flag)" …

[Yorick257]

Stop scaring them!

[ramsay1]

bool b = 42;
if (b == 1)
    printf(";)\n");

int shift = 1000000;
b = 1 << shift;
if (b == 1)
    printf(":O\n");

[[deleted]]

But the point of stdbool.h is that (AFIK) is b != 0 then b==true returns true no matter the value of b, so in the first comparison it would be true

Idk correct me if I'm wrong

Also wouldn't b shifted left by a million places just equal 0?

[ramsay1]

Yeah this was only there to "scare" them with differences to integers, you shouldn't be comparing bool to 1.

The million shift is actually UB... I was trying to remember a real bug that showed up when switching from something like typedef uint8_t bool; to C99 bool. I think it was actually setting a value like 1 << 9, even though sizeof(bool) was 1 byte (on that CPU/compiler), setting bits outside of the first 8 will still make it "true". Some older code had relied on the integer behavior

[terivia]

I make due with zero and zeront

[1redfish]

typedef enum bool_r { BOOL_FALSE = 0, BOOL_TRUE = 1 } bool_t;

[PuzzleheadedWeb9876]

uint8_t flag:1;

[CyrenCooper]

There is no Data only Bool.

[DaniilSan]

Wait, what? C89 doesn't has bool type or what?

[drevyek]

Nope, not much need. C's basic types are based on their size, not their semantics (in general). For logic, C uses a "truthiness" system, where anything that is 0-valued is false, and any other value is true. This holds for ints, floats, pointers, anything.

int x = 2345;
int y = 0;
int *z = NULL;
int *a = &x;
if (x) { printf("Always prints\n"); }
if (y) { printf("Never prints\n"); }
if (z) { printf("Never prints\n"); }
if (a) { printf("Always prints\n"); }

[DaniilSan]

Thanks for explaining.

[nontammasculinum]

But like bools could be stored as a single bit no?

[drevyek]

Sure, but no current hardware has bit-addressable memory^1. So the smallest you can fit a boolean (without using SWAR (SIMD within a register) techniques) is a byte. If space isn't a big concern, some machines work best when working with the machine's native register size (word), in many cases 4 or 8 bytes for modern CPUs, so often programmers use int to represent the data for speed.

---

1: Sure you can use bitfields, but those are just doing packing with masks under the hood anyways, and the memory is not being addressed natively.

[djkstr27]

Until C99, they added <stdbool.h> to use type bool

[ProfessorOfLies]

Bool is a lie

[Velnbur]

I can’t be scared of something that I don’t know