error: 'INT32_MAX' was not declared in this scope

Question

I'm getting the error

error: 'INT32_MAX' was not declared in this scope

But I have already included

#include <stdint.h>

I am compiling this on (g++ (GCC) 4.1.2 20080704 (Red Hat 4.1.2-44) with the command

g++ -m64 -O3 blah.cpp

Do I need to do anything else to get this to compile? or is there another C++ way to get the constant "INT32_MAX"?

Thanks and let me know if anything is unclear!

@IanNorton, maybe you are right, but I still have to see a place where INT32_MAX is a different value — Walter Tross, Jan 08 '14 at 14:35
My Eclipse (Helios)/MinGW setup did not highlight as an error, and I was able to right click and open declaration, but I had to change 'include' to 'include ' in order to stop INT_MAX reporting a 'not declared in this scope' error. — Clarius, Feb 25 '17 at 09:55

score 50 · Answer 1 · edited Feb 05 '19 at 18:16

50

Quoted from the man page, "C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined before <stdint.h> is included".

So try:

#define __STDC_LIMIT_MACROS
#include <stdint.h>

edited Feb 05 '19 at 18:16

Lightness Races in Orbit

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answered Jul 12 '10 at 23:30

Blindy

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Thanks! I missed that when reading the man page -_-, I need to wait 7 min before accepting your answer though... – jm1234567890 Jul 12 '10 at 23:35
1

This should be the accepted answer. Also make sure you put that before any other include files that might include stdint.h without setting that define first. – Keith Johnston Apr 23 '15 at 18:36
2

5 years later... still not the accepted answer :p Thanks, Blindy. That is a big help. – Spencer D May 15 '15 at 18:44
To be fair the accepted answer is just as good, arguably a more C++ way of doing things. This one is good to know too however. – Blindy May 15 '15 at 21:06
Funny thing is that I provided my answer after yours as a supplement. Only since C++11 adds `constexpr` to `numeric_limits::max()` it became a real alternative. – mip Jul 20 '15 at 15:14
Which man page? The quotation seems to be missing a word or two (before _what_ is included?). – Adrian McCarthy Jul 22 '15 at 17:02
As a note, if you are still having problems with this when using a standard before C++ 11, try also including `` (instead of ``). – fakedad Feb 15 '16 at 18:45
2

This was a gcc bug: https://sourceware.org/bugzilla/show_bug.cgi?id=15366 – Technophile Dec 01 '17 at 20:51
@Blindy There was literally a word missing due to poor markup ;) – Lightness Races in Orbit Feb 05 '19 at 18:17
@AdrianMcCarthy Fixed - was just an editorial issue with the answer. Does still need a citation though. – Lightness Races in Orbit Feb 05 '19 at 18:17

mip · Accepted Answer · 2021-03-11T11:18:25.733

27

 #include <cstdint> //or <stdint.h>
 #include <limits>

 std::numeric_limits<std::int32_t>::max();

Note that <cstdint> is a C++11 header and <stdint.h> is a C header, included for compatibility with C standard library.

Following code works, since C++11.

#include <iostream>
#include <limits>
#include <cstdint>

struct X 
{ 
    static constexpr std::int32_t i = std::numeric_limits<std::int32_t>::max(); 
};

int main()
{
    switch(std::numeric_limits<std::int32_t>::max()) { 
       case std::numeric_limits<std::int32_t>::max():
           std::cout << "this code works thanks to constexpr\n";
           break;
    }
    return EXIT_SUCCESS;
}

http://coliru.stacked-crooked.com/a/4a33984ede3f2f7e

edited Mar 11 '21 at 11:18

answered Jul 12 '10 at 23:41

mip

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Note that this isn't equivalent as it can't be used as a compile-time constant (pre-C++0x that is). – Georg Fritzsche Jul 12 '10 at 23:43
1

yes! This is what I am looking for, a C++ way to do it. Thanks – jm1234567890 Jul 12 '10 at 23:44
@Georg Fritzsche: it can be used as compile-time constant. `const int MY_INT32_MAX = std::numeric_limits::max();` will work just fine. This method is so simple that it will be optimized out as it would be explicitly defined constant. – mip Jul 12 '10 at 23:48
1

If you use `` and compile with `-std=c++0x`, `INT32_MAX` is defined as a constant anyway (At least over here it is [GCC 4.4.4]). – tjm Jul 12 '10 at 23:53
5

Doc, its not a *compile-time* constant - you can't use that where the language requires an *integral constant*. Try `switch(1) { case std::numeric_limits::max(): }` or `struct X { static const int i = std::numeric_limits::max(); };`. I'm btw not saying `` is bad, just pointing out a difference. – Georg Fritzsche Jul 13 '10 at 01:50
@GeorgFritzsche you were right, but this should be revised, cause C++0x does have `constexpr` and your examples should work now. – mip Mar 26 '12 at 12:49
2

Pedantic: need to qualify `std::int32_t`, since the `.h` wasn't included and for the sake of good practice in general. – Potatoswatter Jul 22 '15 at 14:55

score 8 · Answer 3 · answered Sep 21 '17 at 02:04

8

Hm... All I needed to do was #include <climits> nothing else on this page worked for me.

Granted, I was trying to use INT_MIN.

answered Sep 21 '17 at 02:04

pixelpax

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Rahul Dutta · Answer 4 · 2019-02-05T18:21:12.930

7

#include <iostream>
#include <limits.h> or <climits>

worked for me

edited Feb 05 '19 at 18:21

answered Feb 05 '19 at 18:14

Rahul Dutta

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score 1 · Answer 5 · answered Aug 05 '19 at 21:29

I ran into similar issue while using LLVM 3.7.1 c++ compiler. Got the following error while trying to compile gRPC code as part of building some custom library

src/core/lib/iomgr/exec_ctx.h:178:12: error: use of undeclared identifier 'INT64_MAX'

The compilation went through after adding -D__STDC_LIMIT_MACROS as one of the options to c++ compiler.

.../bin/c++ -D__STDC_LIMIT_MACROS -I{LIBRARY_PATHS} testlib.cc -o testlib

score 0 · Answer 6 · answered Jun 20 '17 at 22:50

0

Including the following code after #include <iostream> worked for me:

#include <limits.h>

I am using the following compiler:

g++ 5.4.0-6

answered Jun 20 '17 at 22:50

score 0 · Answer 7 · answered Dec 21 '18 at 10:27

0

I was also facing the similar problem,just need to add- #include <limits.h> after #include <iostream>

answered Dec 21 '18 at 10:27

hardik chugh

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score 0 · Answer 8 · answered Dec 27 '21 at 03:01

The code for all c++ version, compatible with lower GCC like CentOS 6.0(gcc version 4.4.7):

// https://onlinegdb.com/ApNzDNYUx

#include <stdio.h>

// @see https://stackoverflow.com/a/9162072/17679565
#include <inttypes.h>

// For CentOS 6(gcc version 4.4.7) or not defined the macro.
#ifndef INT32_MAX
#define INT32_MAX (2147483647)
#endif

int main()
{
    printf("INT32_MAX=%d\n", INT32_MAX);

    return 0;
}

OnlineGDB

Devansh Raut · Answer 9 · 2022-09-10T13:47:21.547

-1

include --> #include <bits/stdc++.h> <--

should look like :

#include<iostream>
using namespace std;
#include <bits/stdc++.h>

edited Sep 10 '22 at 13:47

answered Sep 10 '22 at 13:47

Devansh Raut

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score -2 · Answer 10 · edited Jan 16 '22 at 06:01

-2

#include<bits/stdc++.h>

add this at the beginning.

edited Jan 16 '22 at 06:01

Suraj Rao

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answered Jan 16 '22 at 06:01

Anurag Singh

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[Why should I not #include ?](https://stackoverflow.com/q/31816095/1458097) – heap underrun Jan 16 '22 at 06:36

error: 'INT32_MAX' was not declared in this scope

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