maximum value of int

Asked 6/12, 2009 at 13:59 Answered 25/4, 2019 at 6:11

222

Is there any code to find the maximum value of integer (accordingly to the compiler) in C/C++ like Integer.MaxValue function in java?

Coltson answered 6/12, 2009 at 13:59 Comment(6)

is there any way to find the max value of long long int?? – Coltson 6/12, 2009 at 14:29

Just replace int with long long int in Gregories answer... – Darksome 6/12, 2009 at 14:43

except that long long is not part of C++ – Aprylapse 6/12, 2009 at 14:44

Duplicate of e.g. https://mcmap.net/q/120460/-c-max-integer-duplicate – Darksome 6/12, 2009 at 14:45

@Neil, right, its C99 - but VC and GCC (without -pedantic) support it. – Darksome 6/12, 2009 at 14:58

Don't confuse int with "integer". There are several integer types; int is just one of them. – Jodiejodo 27/9, 2014 at 21:41

390

In C++:

#include <limits>

then use

int imin = std::numeric_limits<int>::min(); // minimum value
int imax = std::numeric_limits<int>::max();

std::numeric_limits is a template type which can be instantiated with other types:

float fmin = std::numeric_limits<float>::min(); // minimum positive value
float fmax = std::numeric_limits<float>::max();

In C:

#include <limits.h>

then use

int imin = INT_MIN; // minimum value
int imax = INT_MAX;

#include <float.h>

float fmin = FLT_MIN;  // minimum positive value
double dmin = DBL_MIN; // minimum positive value

float fmax = FLT_MAX;
double dmax = DBL_MAX;

Birecree answered 6/12, 2009 at 14:0 Comment(7)

Note that the floating-point min are the minimum positive value, where as the integer min are the minimum value. Same goes for the C macros/constants. – Runt 31/12, 2009 at 11:29

in C99 you can also use UINT64_MAX and INT64_MAX – Georgy 2/10, 2013 at 9:8

@DmitryVyal: Yes you can, but those are the limits of uint64_t and int64_t, not of int. – Jodiejodo 27/9, 2014 at 21:45

In C++, I used the same code shown above: #include <limits> and int imax = std::numeric_limits<int>::max();, but I get the error Can't resolve struct member 'max'. Any ideas as to why this occurs, and how to fix it? I am using CLion IDE, with CMake and C++ 11 on Ubuntu 14.04. I think it is linked to this issue – Interclavicle 10/10, 2014 at 20:15

Hopefully this helps someone, because it was a CLion IDE bug that I fixed by using the latest CLion (build 138.2344 - CLion is in the Early Access Program phase, and thus unstable) – Interclavicle 10/10, 2014 at 20:34

a fancy way would be like so (unsigned)-1/2 – Valley 21/2, 2019 at 20:35

I want to use <limits> is on an Arduino but it does not exist. "No such file or directory" – Biform 14/8, 2020 at 15:16

I know it's an old question but maybe someone can use this solution:

int size = 0; // Fill all bits with zero (0)
size = ~size; // Negate all bits, thus all bits are set to one (1)

So far we have -1 as result 'till size is a signed int.

size = (unsigned int)size >> 1; // Shift the bits of size one position to the right.

As Standard says, bits that are shifted in are 1 if variable is signed and negative and 0 if variable would be unsigned or signed and positive.

As size is signed and negative we would shift in sign bit which is 1, which is not helping much, so we cast to unsigned int, forcing to shift in 0 instead, setting the sign bit to 0 while letting all other bits remain 1.

cout << size << endl; // Prints out size which is now set to maximum positive value.

We could also use a mask and xor but then we had to know the exact bitsize of the variable. With shifting in bits front, we don't have to know at any time how many bits the int has on machine or compiler nor need we include extra libraries.

Ought answered 22/4, 2015 at 10:55 Comment(1)

cout << "INT_MAX:\t"  << (int) ((~((unsigned int) 0)) >> 1) << '\n'          << "UINT_MAX:\t" << ~((unsigned int) 0)                << endl;

– Bate 18/3, 2017 at 23:13

#include <climits>
#include <iostream>
using namespace std;

int main() {
  cout << INT_MAX << endl;
}

Aprylapse answered 6/12, 2009 at 14:1 Comment(8)

I wouldn't call INT_MAX "a solution for C". It's old-school and deprecated in C++, though. – Siloxane 6/12, 2009 at 14:8

I think both are C++ answers. numeric_limits<int>::max() - works also in template contexts, but (for some unfathomable reason to me) cannot be used as a compile-time constant. INT_MAX - is a macro, pretty useless within template functions, but can be used as a compile-time constant. – Fredela 6/12, 2009 at 14:9

The funny thing is that numeric_limits<int>::max implementation on msvc looks like this: return (INT_MAX); – Pieeyed 6/12, 2009 at 14:11

@paul Reference for the deprecation please. And guess how numeric_limits implements max()? That's right, "return INT_MAX", at least on GCC 4.4.0. – Aprylapse 6/12, 2009 at 14:14

@UncleBens: inline functions currently can't be reduced to constant expressions. – Darksome 6/12, 2009 at 15:4

Yes, I realized it has to be a function in the first place because numeric_limits has to be usable for non-integer types as well. – Fredela 6/12, 2009 at 15:32

@gf: In C++1x they may, using constexpr. – Runt 31/12, 2009 at 11:31

@Runt But most compilers still do not support constexpr sufficiently. – Chaldea 4/10, 2014 at 0:8

Why not write a piece of code like:

int  max_neg = ~(1 << 31);
int  all_ones = -1;
int max_pos = all_ones & max_neg;

Claque answered 22/3, 2012 at 14:46 Comment(1)

There is no guarantee that int is 32 bits in size and there is no guarantee about the in memory negative integer format. Less importantly, there is no need to make people look up '~'. – Glace 14/12, 2012 at 2:19

Here is a macro I use to get the maximum value for signed integers, which is independent of the size of the signed integer type used, and for which gcc -Woverflow won't complain

#define SIGNED_MAX(x) (~(-1 << (sizeof(x) * 8 - 1)))

int a = SIGNED_MAX(a);
long b = SIGNED_MAX(b);
char c = SIGNED_MAX(c); /* if char is signed for this target */
short d = SIGNED_MAX(d);
long long e = SIGNED_MAX(e);

Chandachandal answered 13/6, 2016 at 8:40 Comment(0)

O.K. I neither have rep to comment on previous answer (of Philippe De Muyter) nor raise it's score, hence a new example using his define for SIGNED_MAX trivially extended for unsigned types:

// We can use it to define limits based on actual compiler built-in types also: 
#define INT_MAX   SIGNED_MAX(int)
// based on the above, we can extend it for unsigned types also:
#define UNSIGNED_MAX(x) (  (SIGNED_MAX(x)<<1) | 1 ) // We reuse SIGNED_MAX
#define UINT_MAX  UNSIGNED_MAX(unsigned int) // on ARM: 4294967295
// then we can have:
unsigned int width = UINT_MAX;

Unlike using this or that header, here we use the real type from the compiler.

Curule answered 18/3, 2017 at 22:44 Comment(0)

#include <iostrema>

int main(){
    int32_t maxSigned = -1U >> 1;
    cout << maxSigned << '\n';
    return 0;
}

It might be architecture dependent but it does work at least in my setup.

Burrton answered 25/4, 2019 at 6:11 Comment(1)

This may work, but it's important to strive for portability. – Cussed 14/3, 2022 at 2:11

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