Unclear about Order of passing arguments while callng a function in C programming

Question

Unclear about Order of passing arguments while callng a function in C programming

Anonymous

I want to know the preference order of passing arguments while calling a function in C programming. Actually i am getting different-different answer, so help me out. Here are the two sets of C program.

1-

include<stdio.h>

int main()
{
int a = 1;
printf("%d\t%d\t%d\n", a,++a, a++);
return 0;
}

2-

include<stdio.h>

int main()
{
int a = 1;
printf("%d\t%d\t%d\n", --a,++a, a++);
return 0;
}

3-

include<stdio.h>

int main()
{
int a = 5;
printf("%d\t%d\t%d\n", --a,++a,a--);
return 0;
}

Barry Schwarz 3,746 Reputation points

2021-05-13T17:56:49.007+00:00
In addition to the reference provided, you should be aware that the order of evaluating the arguments is unspecified. Consequently, even without undefined behavior, if evaluating one argument could affect the evaluation of a different argument, the code in question could produce different results depending on the order of evaluation. Since the order of evaluation is unspecified, the compiler is free to change the order of evaluation based on optimization settings, time when the program is being compiled, phase of the moon, or any other criteria it chooses. Consider the following:

#include <stdio.h> int x = 5; int f(int y) { x = y; return y; } int main(void) { printf("%d %d %d\n", f(1), f(2), x); return 0; }

The first two values printed must be 1 and 2 but the third could be 1, 2, or 5. For a single compilation, the value will never change but if you recompile the program it could.

1 answer

Your answer

Barry Schwarz 3,746 Reputation points

2021-05-13T17:56:49.007+00:00

In addition to the reference provided, you should be aware that the order of evaluating the arguments is unspecified. Consequently, even without undefined behavior, if evaluating one argument could affect the evaluation of a different argument, the code in question could produce different results depending on the order of evaluation. Since the order of evaluation is unspecified, the compiler is free to change the order of evaluation based on optimization settings, time when the program is being compiled, phase of the moon, or any other criteria it chooses. Consider the following:

#include <stdio.h> int x = 5; int f(int y) { x = y; return y; } int main(void) { printf("%d %d %d\n", f(1), f(2), x); return 0; }

The first two values printed must be 1 and 2 but the third could be 1, 2, or 5. For a single compilation, the value will never change but if you recompile the program it could.

Answer 1

RLWA32 49,551

Here's a link to get you started reading about C and undefined behavior - why-are-these-constructs-using-pre-and-post-increment-undefined-behavior

Share via

Unclear about Order of passing arguments while callng a function in C programming

include<stdio.h>

include<stdio.h>

include<stdio.h>

1 answer

Your answer