long long in C C

Question

I am trying this code on GNU s C   compiler and am unable to understand its behaviour    include  lt stdio h gt    int main         int  num1   1000000000      long num2   1000000000      long long num3        num3   100000000000      long long num4    0       printf   u  u  u   sizeof num1   sizeof num2   sizeof num3        printf   d  ld  lld  llu   num1  num2  num3  num4       return 0      When I uncomment the commented line  the code doesn t compile and is giving an error      error  integer constant is too large for long type   But  if the code is compiled as it is and is executed  it produces values much larger than 10000000000   Why

User · Accepted Answer

The letters 100000000000 make up a literal integer constant, but the value is too large for the type int. You need to use a suffix to change the type of the literal, i.e.

long long num3 = 100000000000LL;

The suffix LL makes the literal into type long long. C is not "smart" enough to conclude this from the type on the left, the type is a property of the literal itself, not the context in which it is being used.

User · Answer

Try   num3   100000000000LL    And BTW  in C   this is a compiler extension  the standard does not define long long  thats part of C99

User · Answer

It depends in what mode you are compiling  long long is not part of the C   standard but only  usually  supported as extension  This affects the type of literals  Decimal integer literals without any suffix are always of type int if int is big enough to represent the number  long otherwise  If the number is even too big for long the result is implementation-defined  probably just a number of type long int that has been truncated for backward compatibility   In this case you have to explicitly use the LL suffix to enable the long long extension  on most compilers    The next C   version will officially support long long in a way that you won t need any suffix unless you explicitly want the force the literal s type to be at least long long  If the number cannot be represented in long the compiler will automatically try to use long long even without LL suffix  I believe this is the behaviour of C99 as well

User · Answer

your code compiles here fine  even with that line uncommented  had to change it to  num3   100000000000000000000    to start getting the warning

[c++] long long in C/C++

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