0

I am using Windows-11, 64-bit, and Dev-C++ (Bloodshed v5.11); the following is the simple code snippet:-

#include<stdio.h>

int main()
{
    return -1;
}

I am getting the following output in the console:-

Process exited after 0.2015 seconds with return value 4294967295 Press any key to continue . . .

In the output, I do recognize that 4294967295 (2^32 - 1) is the max value of the unsigned 4-byte integer, but I cannot understand why this value is returned instead of "-1".

Ashish Jog
  • 11
  • 3
  • 1
    It's the *same* bit pattern `0xFFFFFFFF` (in 2's complement representation) and `unsigned` must be how the shell interprets it. – Weather Vane Nov 11 '21 at 17:18
  • Hi, Weather Vane, Sorry but I do not understand what you tried to explain, can you elaborate or suggest some text to read, and why the question is closed ? – Ashish Jog Nov 11 '21 at 17:20
  • Everything in the computer is a number, and what that number means depends on context. The `0xFFFFFFFF` returned was `-1` to the function that returned it, and `4294967295` to the function that received it, for some reason of the implementation. They are the same set of bits, treated in a different context. – Weather Vane Nov 11 '21 at 17:23
  • 1
    This is a behavior of the console or command line program, not your program. – aschepler Nov 11 '21 at 17:23
  • 1
    It is a mismatch between the C language specification and the [operating system](https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getexitcodeprocess). Which uses DWORD for the exit status, an unsigned integer type. No biggie, but it is best to reserve negative values for program aborts. – Hans Passant Nov 11 '21 at 17:49

1 Answers1

1

-1 in two's complement signed number format (assuming 4 bytes long integers) is 0xffffffff which is the maximum unsigned value that can be stored in the 4 bytes. Two's complement format is used by almost all computers used nowadays (including your PC, Mac and any mobile phone)

Your shell is displaying the program return value as unsigned integer. The decimal representation of the 0xffffffff hex number is 4294967295

0___________
  • 60,014
  • 4
  • 34
  • 74
  • Not a 2's complement issue. -1 encode as a non-2's complement, when assigned to a 32-bit unsigned would still have the value 4294967295. This is a _signed_ versus _unsigned_ type issue, not an encoding one. – chux - Reinstate Monica Nov 11 '21 at 19:27
  • @chux-ReinstateMonica you assume that shell was written in C and it has assigned the variable. But if the language is not following the C rules or code in shell simple memcpy the return value. Then -1, if ones complement is used, will be 4294967294. You do not know what shell is doing with the return value. So I do not agree with your comment as it covers only one of many possibilities – 0___________ Nov 11 '21 at 19:35