C++ Literal suffix behavior

code.cpp

#include <iostream>

using namespace std;

int main()
{
	// Likely to generate a warning.
	unsigned long long limit63bit = 18446744073709551615; // 2^64 - 1

	// OK
	unsigned long long limit56bit = 18446744073709551615u;

	cout << limit63bit << " " << limit56bit << endl;

	return 0;
}

compilation-result.md

Result on compilation:

• With C++98

himanshu-dell ➜  /tmp g++ sample.cpp -Wall -std=c++98 && ./a.out 
sample.cpp:8:34: warning: integer constant is so large that it is unsigned
  unsigned long long limit63bit = 18446744073709551615; // 2^64 - 1
                                  ^~~~~~~~~~~~~~~~~~~~
sample.cpp:8:2: warning: this decimal constant is unsigned only in ISO C90
  unsigned long long limit63bit = 18446744073709551615; // 2^64 - 1
  ^~~~~~~~
18446744073709551615 18446744073709551615

• With C++11

himanshu-dell ➜  /tmp g++ sample.cpp -Wall -std=c++11 && ./a.out 
sample.cpp:8:34: warning: integer constant is so large that it is unsigned
  unsigned long long limit63bit = 18446744073709551615; // 2^64 - 1
                                  ^~~~~~~~~~~~~~~~~~~~
18446744073709551615 18446744073709551615

intro.md

The code is taken from https://stackoverflow.com/a/40265895/5163807 Find more here: https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.1.0/com.ibm.zos.v2r1.cbclx01/lit_integer.htm and https://stackoverflow.com/questions/13134956/what-is-the-reason-for-explicitly-declaring-l-or-ul-for-long-values