What should be the sizeof int on a 64-bit machine

Question

Possible Duplicate    size of int  long  etc   Does the size of an int depend on the compiler and or processor    What decides the sizeof an integer        I m using a 64-bit machine     uname -m x86 64   file  usr bin file  usr bin file  ELF 64-bit LSB executable  x86-64  version 1  SYSV   dynamically linked  uses shared libs   for GNU Linux 2 6 32  stripped      When I ran the following program  I got the sizeof int  as 4-bytes    include  lt stdio h gt   int main void        printf  sizeof int     d bytes n    int  sizeof int         return 0      If I m running a 16-  32- and 64- bit machine  then doesn t it mean that the size of an integer is 16-  32- and 64- bit respectively   In my machine  I found the WORD BIT is 32  Shouldn t it be 64 on a 64-bit machine      getconf WORD BIT 32      And  shouldn t the sizeof int  be 64-bits  8 bytes  in the above case

User · Accepted Answer

Doesn t have to be   64-bit machine  can mean many things  but typically means that the CPU has registers that big   The sizeof a type is determined by the compiler  which doesn t have to have anything to do with the actual hardware  though it typically does   in fact  different compilers on the same machine can have different values for these

User · Answer

Size of a pointer should be 8 byte on any 64-bit C C   compiler  but not necessarily size of int

User · Answer

In C    the size of int isn t specified explicitly  It just tells you that it must be at least the size of short int  which must be at least as large as signed char  The size of char in bits isn t specified explicitly either  although sizeof char  is defined to be 1  If you want a 64 bit int  C  11 specifies long long to be at least 64 bits

User · Answer

Not really  for backward compatibility it is 32 bits  If you want 64 bits you have long  size t or int64 t

[c++] What should be the sizeof(int) on a 64-bit machine?

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