stdckdint.h bug report

[ander_cc]

Yesterday，I learn some c23 new features. Maybe there is a bug in stdckdint.h.

bool ckd_add( type1 *result, type2 a, type3 b );
bool ckd_sub( type1 *result, type2 a, type3 b );
bool ckd_mul( type1 *result, type2 a, type3 b );

Macros always return false. Pelles c 13.01. Windows 11 Simplified Chinese.

Code Select Expand

#include <stdio.h>
#include <stdckdint.h>
int main(void)
{
int a = 655350;
int b = 10;
short int c = 0;
//int c = 0;
bool result = true;
result = ckd_mul(&c, a, b); // ckd_add(&c, a, b); ckd_sub(&c, a, b);
if (result == true) {
puts("true\n");
}else{
puts("false\n");
}
printf("c = %d\n", c);
return 0;
}

[John Z]

Hi Ander,

Well not always - If the numbers are big enough to 'wrap' you'll get 'true'
for example - output from code below :
true
c = -13107100
false
c = 1310700
false
c = 0
Press any key to continue...

Code Select Expand

#include <stdio.h>
#include <stdckdint.h>
int main(void)
{
    long int a = 655350;
    long int b = 655350;//10
    int c = 0;
    //int c = 0;
    bool result = true;
    result = ckd_mul(&c, a, b); // ckd_add(&c, a, b); ckd_sub(&c, a, b);
    if (result == true) {
        puts("true\n");
    }else{
        puts("false\n");
    }
    printf("c = %d\n", c);   
    result =  ckd_add(&c, a, b); // ckd_sub(&c, a, b);
    if (result == true) {
        puts("true\n");
    }else{
        puts("false\n");
    }
    printf("c = %d\n", c);
    result = ckd_sub(&c, a, b);
    if (result == true) {
        puts("true\n");
    }else{
        puts("false\n");
    }
    printf("c = %d\n", c);
    return 0;
}
Cheers,
John Z

[TimoVJL]

https://cppreference.net/c/numeric/ckd_mul.html

Just easier to read:

Code Select Expand

#include <stdio.h>
#include <stdckdint.h>
char *ab[] = {"false", "true "};
int main(void)
{
    long int a = 655350;
    long int b = 655350;//10
    int c = 0;
    bool result;
    result = ckd_mul(&c, a, b); // ckd_add(&c, a, b); ckd_sub(&c, a, b);
    printf("result: %s c = %d\n", ab[result], c);

    result =  ckd_add(&c, a, b); // ckd_sub(&c, a, b);
    printf("result: %s c = %d\n", ab[result], c);

    result = ckd_sub(&c, a, b);
    printf("result: %s c = %d\n", ab[result], c);
    return 0;
}


[John Z]

👍👍👍

Definitely!  Thanks Timo.
Better output too -

Code Select Expand

    long int a = 65536;
    long int b = 65535;//10
    int c = 0;
---------output---------
result: true  c = -65536
result: false c = 131071
result: false c = 1
Press any key to continue...
John Z

[ander_cc]

https://cppreference.net/c/numeric/ckd_mul.html

thank you for your reply,  TimoVJL. I have read it. please try my test code.
Pelles C 13.01 will print :
false
c = 0
but gcc 15.2 will print :
true
c = 0

And I read the Pelles C help file for "stdckdint.h". I think the return value depends on first argument type. But Pelles C returns false when the first argument overflow in following code.

Code Select Expand

#include <stdio.h>
#include <stdckdint.h>
int main(void)
{
int a = 655350;
int b = 10;
short int c = 0;

bool result = true;
result = ckd_add(&c, a, b); //out of range of short. a and b are int, c is short int.
if (result == true)
{
puts("true");
}else{
puts("false");
}
printf("c = %d ", c);

return 0;
}


[ander_cc]

👍👍👍

Definitely!  Thanks Timo.
Better output too -

Code Select Expand

    long int a = 65536;
    long int b = 65535;//10
    int c = 0;
---------output---------
result: true  c = -65536
result: false c = 131071
result: false c = 1
Press any key to continue...
John Z

Thank you for your reply, John Z.
The "long int" and the "int" are 32bit value in Pelles c.
I get the false when only the first argument overflow in function ckd_add, I think it is a bug.

Code Select Expand

#include <stdio.h>
#include <stdckdint.h>
int main(void)
{
int a = 655350;
int b = 10;
short int c = 0;

bool result = true;
result = ckd_add(&c, a, b); //out of range of short. a and b are int, c is short int.
if (result == true)
{
puts("true");
}else{
puts("false");
}
printf("c = %d ", c);

return 0;
}


[TimoVJL]

with dataset:

Code Select Expand

    int a = 655350;
    int b = 10;
    short c = 0;
Clang output:

Code Select Expand

true  c = -100
true  c = 0
true  c = -20