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#11

Bug reports / Re: bug report. setvbuf() func...

Last post by TimoVJL - March 09, 2026, 05:31:09 PM

simpler check

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#include <stdio.h>

int main(void)
{
    setvbuf(stdout, NULL, _IOFBF, 7000);
    for (int i = 0; i <= 1351; i++)
        printf("%d?\n", i);
   
    return 0;
}
output:

Code Select Expand

...
1328?
329?
1330?
1331?
1332?
1333?
1334?
1335?
1336?
1337?
1338?
1339?
1340?
1341?
1342?
1343?
1344?
1345?
1346?
1347?
1348?
1349?
1350?
13511351?

Code Select Expand

'1157'
'1151158'
'1159'size: 7003

#12

Bug reports / Re: bug report. setvbuf() func...

Last post by ander_cc - March 09, 2026, 02:26:45 PM

https://en.cppreference.com/w/c/io/setvbuf
buffer size should be at least multiple of 2

I have read it last week. "the actual buffer size is usually rounded down to a multiple of 2". Just NOT use some bytes, so any number is OK.

I try it at home, my laptop. see picture.
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#13

Bug reports / Re: stdckdint.h bug report

Last post by TimoVJL - March 09, 2026, 12:10:59 PM

with dataset:

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

Code Select Expand

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

#14

Bug reports / Re: bug report. setvbuf() func...

Last post by TimoVJL - March 09, 2026, 11:54:49 AM

https://en.cppreference.com/w/c/io/setvbuf
buffer size should be at least multiple of 2

#15

Bug reports / Re: bug report. setvbuf() func...

Last post by ander_cc - March 09, 2026, 10:10:37 AM

Hi ander,

I could not reproduce this.  With the setvbuf 1000, 5000, 7000, or not even use setvbuf it always ends the loop on 20000 .  I just pasted your code in. 

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19998
19999
20000
Press any key to continue...
John Z

thank you for test.
I changed the number and try it again, and got different result, I got a new line "00".
Windows 11 Pro 25H2 simplified chinese. Only for chinese windows? I will try it on my laptop at home later

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#16

Bug reports / Re: bug report. setvbuf() func...

Last post by John Z - March 09, 2026, 09:56:30 AM

Hi ander,

I could not reproduce this.  With the setvbuf 1000, 5000, 7000, or not even use setvbuf it always ends the loop on 20000 .  I just pasted your code in. 

Code Select Expand

19998
19999
20000
Press any key to continue...
John Z

#17

Bug reports / bug report. setvbuf() function...

Last post by ander_cc - March 09, 2026, 07:53:45 AM

I have learned setvbuf() function last week. But got a strange error.
The setvbuf function last argument is buffer size. When I set 1000, 2000, 3000, 4000, will be OK, but when I set it to 5000 or 7000, I will get a additional line.
Then, I try the same code in gcc 15.2, it is correct.

Code Select Expand

#include <stdio.h>

int main(void)
{
setvbuf(stdout, NULL, _IOFBF, 7000);
for (int i = 0; i < 20001; i++)
printf("%d\n", i);

return 0;
}You cannot view this attachment.

[only]

#18

Bug reports / Re: stdckdint.h bug report

Last post by ander_cc - March 09, 2026, 07:30:13 AM

👍👍👍

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;
}


[Pelles C 13.01 will print :]

#19

Bug reports / Re: stdckdint.h bug report

Last post by ander_cc - March 09, 2026, 07:23:31 AM

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;
}


#20

Bug reports / Re: stdckdint.h bug report

Last post by John Z - March 08, 2026, 09:26:14 PM

👍👍👍

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