C Struct with uint8 array weird behavior

Question

I have problem with following C struct:

typedef struct AnchorPixel{
    int32 X;
    int32 Y;
    uint8 CH[5];
} AnchorPixel;

Actually, I have problem with CH array inside it. I just cannot manipulate CH array. For example, following program

AnchorPixel a;
a.CH[2] = 5;
cout << a.CH[2];

gives output:

♣

If I change CH type from uint8 to int32, problem disappears. This works:

typedef struct AnchorPixel{
        int32 X;
        int32 Y;
        int32 CH[5]; 
    } AnchorPixel;

Any ideas?

uint8_t is probably typedef'ed as a char ... I am guessing that is what uint8 really is. — Shafik Yaghmour
– Shafik Yaghmour, Commented Apr 29, 2015 at 17:05
Also since I see cout I am guessing this should really be tagged C++ — Shafik Yaghmour
– Shafik Yaghmour, Commented Apr 29, 2015 at 17:06
This works AnchorPixel a; a.CH[2] = 5; cout << (int32)a.CH[2]; — Bogdan
– Bogdan, Commented Apr 29, 2015 at 17:15
Which comment and I right about? About tagging this C++ or about the typedef? — Shafik Yaghmour
– Shafik Yaghmour, Commented Apr 29, 2015 at 17:15

Shafik Yaghmour · Accepted Answer · 2015-04-30 19:17:23Z

1

It seems likely that uint8 is typedef'ed as a unsigned char, we can see on coliru for uint8_t this is the case. The cstdint header includes stdint.h and there uint8_t is indeed a typedef to unsigned char:

typedef unsigned char       uint8_t;

The output you are seeing is consistent with cout treating a.CH[2] as a char type,

edited Apr 30, 2015 at 19:17

answered Apr 29, 2015 at 17:15

Shafik Yaghmour

160k44 gold badges466 silver badges778 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

C Struct with uint8 array weird behavior

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related