nixCraft

Rick · #1 (**permalink**) 30-06-2006, 11:50 PM

Hi all,

I can't figure out how to remove a single warning in my project.
Example code:

typedef long long int_64;

void write_integer(int x, int y, int_64 i)
{
char number[35];
sprintf(number, "%u", i);
//code that passes number to string write function
}

When I compile this on linux (gcc with option -Wall) I get the warning:
warning: unsigned int format, different type arg (arg 3)
The sprintf does work for numbers larger then 32 bit though, the output is correct.

Is there a good way to satisfy the compiler?
And if there isn't, is there a way to hide a single warning?

Thank you,
Rick.

nixcraft · #2 (**permalink**) 02-07-2006, 12:01 AM

Rick, I am getting following warning:

Code:

file.c: In function 'write_integer':
file.c:6: warning: incompatible implicit declaration of built-in function 'sprintf'

To fix above error i just use #include<stdio.h>

May be you need to put complete function code here so that we can help you

Rick · #3 (**permalink**) 02-07-2006, 05:10 PM

Thank you for your reply nixcraft.

This is the complete code that reproduces the warning:

example.cpp :

Code:

#include <stdio.h>
#include <string.h>

typedef long long int_64;

int main(void)
{
    char buffer[51];
    int_64 huge_number = 2000000000 * 4;
    memset(buffer, 0, 50);
    sprintf(buffer, "%u", huge_number);
    printf("Result: %s\n", buffer);
    return 0;
}

Compile it with the command:

Code:

gcc -lstdc++ -Wall example.cpp -o example

The compiler output:

Code:

example.cpp: In function `int main()':
example.cpp:11: warning: unsigned int format, different type arg (arg 3)

When I run it:

Code:

./example
Result: 3705032704

Quote:

Originally Posted by rick

The sprintf does work for numbers larger then 32 bit though, the output is correct.

That seems to be untrue.
In this example 2000000000 * 4 should be 8000000000 instead of 3705032704.
So it seems the compiler warning is right.

That leaves the question: How can I convert a very large number (over 32 bits) to a string?

nixcraft · #4 (**permalink**) 02-07-2006, 07:26 PM

Do not use %u for large unsigned int format, use %llu i.e.
Replace

Code:

sprintf(buffer, "%u", huge_number);

With

Code:

sprintf(buffer, "%llu", huge_number);

Rick · #5 (**permalink**) 03-07-2006, 12:00 AM

Thank you !

It works like a charm.

I'm a Delphi programmer for windows.
Recently I started to play with C++ and gcc.
Linux is way more strict then Windows, which is good IMO.
I just encounter a lot of unknowns

Thank you for helping.

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nixCraft

Fix sprintf warning

Fix sprintf warning

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