macOS [SOLVED] Minimum C int value

[Eraserhead]

A quick question

How to you get the minimum value for int programmatically in C/Obj-C?

Thanks

 

[Gelfin]

I'm fairly certain there's a more optimal and less ugly way to do this, but this will accomplish what you need, and it's the first thing that sprung to mind. Note that this will be accurate whether int is 32 or 64 bits wide.

#include <stdio.h>
void main(void)
{
	int nMin = 8;
	unsigned int* pMin = (unsigned int*)&nMin;
	while(0 != (*pMin << 4)) *pMin <<= 4;
	printf("INT_MIN: %d\n", nMin);
}

 

[Gelfin]

Here's an enhanced version that calculates everything you might want to know about local integers:

#include <stdio.h>
void main(void)
{
	int nMin = 8;
	int nMax = 0;
	int nWidth = 8;
	while(0 < (nMin <<= 4)) nWidth += 4;
	nMax = nMin^-1;
	printf("Integers on your system are %d bits wide.\n", nWidth);
	printf("The maximum integer is %d.\n", nMax);
	printf("The minimum integer is %d.\n", nMin);
}

 

[iSee]

You could use this snippit:

1 << (sizeof(int) * 8 - 1)

But it's probably better to #include <limits.h> and use INT_MIN

(as far as I know, limits.h and INT_MIN are cross-platform.)

here's a little test program:

#include <stdio.h>
#include <limits.h>

int main(int argc, char* argv[])
{
	printf("%d %d\n", 1 << (sizeof(int) * 8 - 1), INT_MIN);
	return 0;
}

 

[Eraserhead]

But it's probably better to #include <limits.h> and use INT_MIN

That's exactly what I wanted, brilliant!

 

[gnasher729]

You could use this snippit:

1 << (sizeof(int) * 8 - 1)

... and I have seen compilers where this will give you a value of +32768, while INT_MIN had a value of -2,147,483,648. 😡

 

[Gelfin]

But it's probably better to #include <limits.h> and use INT_MIN

(as far as I know, limits.h and INT_MIN are cross-platform.)

Well, first off I assumed "programmatically" meant "calculate it," but second, check /usr/include/limits.h before you make any assumptions. I checked that first, and you'll be surprised. 🙂

Well, first off I assumed "programmatically" meant "calculate it," but second, check /usr/include/limits.h before you make any assumptions. I checked that first, and you'll be surprised. 🙂

Ah, never mind. They buried it down in i386/limits.h. Just had to crawl through all the nested includes to find it. This'll work.

 

[lazydog]

I assumed "programmatically" meant "calculate it

I think this will also work… it gives the same result as INT_MIN anyway.

int minlimit = (int)( ( ( (unsigned int) -1 ) >> 1 ) + 1 ) ;

b e n

 

[Eraserhead]

The numbers are all going to be fairly reasonable with what I am doing, (really 0 to 10 or so) so even -32000 would be OK here.