c++ - error: 'INT32_MAX' was not declared in this scope - Stack Overflow

Asked 10 years, 11 months ago

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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!

c++

asked Jul 12 '10 at 23:27

jm1234567890

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@WalterTross baaaad baad idea, – IanNorton Jan 8 '14 at 10:17
@IanNorton, maybe you are right, but I still have to see a place where INT32_MAX is a different value – Walter Tross Jan 8 '14 at 14:35
My Eclipse (Helios)/MinGW setup did not highlight <limits> as an error, and I was able to right click and open declaration, but I had to change 'include<limits>' to 'include <limits.h>' in order to stop INT_MAX reporting a 'not declared in this scope' error. – Clarius Feb 25 '17 at 9:55

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7 Answers

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#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 at 11:18

answered Jul 12 '10 at 23:41

doc

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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 FritzscheJul 12 '10 at 23:43
1
yes! This is what I am looking for, a C++ way to do it. Thanks – jm1234567890Jul 12 '10 at 23:44
1
If you use <cstdint> and compile with -std=c++0x, INT32_MAX is defined as a constant anyway (At least over here it is [GCC 4.4.4]). – tjmJul 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<int32_t>::max(): } or struct X { static const int i = std::numeric_limits<int32_t>::max(); };. I'm btw not saying <limits> is bad, just pointing out a difference. – Georg FritzscheJul 13 '10 at 1:50
2
Pedantic: need to qualify std::int32_t, since the .h wasn't included and for the sake of good practice in general. – PotatoswatterJul 22 '15 at 14:55

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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 5 '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... – jm1234567890Jul 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 JohnstonApr 23 '15 at 18:36
2
5 years later... still not the accepted answer :p Thanks, Blindy. That is a big help. – Spencer DMay 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. – BlindyMay 15 '15 at 21:06
2
This was a gcc bug: sourceware.org/bugzilla/show_bug.cgi?id=15366– TechnophileDec 1 '17 at 20:51

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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 2:04

pixelpax

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

worked for me

edited Feb 5 '19 at 18:21

answered Feb 5 '19 at 18:14

Rahul Dutta

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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

user8024721

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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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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

answered Aug 5 '19 at 21:29

Ram

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