Variable Number of Arguments Questions

• Point out the error in the following program. #include<stdio.h> #include<stdarg.h> fun(...); int main() { fun(3, 7, -11.2, 0.66); return 0; } fun(...) { va_list ptr; int num; va_start(ptr, n); num = va_arg(ptr, int); printf("%d", num); }
• Point out the error in the following program. #include<stdio.h> #include<stdarg.h> int main() { void display(int num, ...); display(4, 12.5, 13.5, 14.5, 44.3); return 0; } void display(int num, ...) { float c; int j; va_list ptr; va_start(ptr, num); for(j=1; j<=num; j++) { c = va_arg(ptr, float); printf("%f", c); } }
• Point out the error in the following program. #include<stdio.h> #include<stdarg.h> int main() { void display(char *s, int num1, int num2, ...); display("Hello", 4, 2, 12.5, 13.5, 14.5, 44.0); return 0; } void display(char *s, int num1, int num2, ...) { double c; char s; va_list ptr; va_start(ptr, s); c = va_arg(ptr, double); printf("%f", c); }
• Point out the error if any in the following program (Turbo C). #include<stdio.h> #include<stdarg.h> void display(int num, ...); int main() { display(4, 'A', 'a', 'b', 'c'); return 0; } void display(int num, ...) { char c; int j; va_list ptr; va_start(ptr, num); for(j=1; j<=num; j++) { c = va_arg(ptr, char); printf("%c", c); } }
• Point out the error in the following program. #include<stdio.h> #include<stdarg.h> void varfun(int n, ...); int main() { varfun(3, 7, -11, 0); return 0; } void varfun(int n, ...) { va_list ptr; int num; num = va_arg(ptr, int); printf("%d", num); }
• Point out the error in the following program. #include<stdio.h> #include<stdarg.h> void display(char *s, ...); void show(char *t, ...); int main() { display("Hello", 4, 12, 13, 14, 44); return 0; } void display(char *s, ...) { show(s, ...); } void show(char *t, ...) { int a; va_list ptr; va_start(ptr, s); a = va_arg(ptr, int); printf("%f", a); }
• Point out the error in the following program. #include<stdio.h> #include<stdarg.h> void varfun(int n, ...); int main() { varfun(3, 7, -11.2, 0.66); return 0; } void varfun(int n, ...) { float *ptr; int num; va_start(ptr, n); num = va_arg(ptr, int); printf("%d", num); }
• The macro va_start is used to initialise a pointer to the beginning of the list of fixed arguments.
• A function that receives variable number of arguments should use va_arg() to extract the last argument from the variable argument list.
• va_list is an array that holds information needed by va_arg and va_end
• The macro va_arg is used to extract an argument from the variable argument list and advance the pointer to the next argument.
• A function that receives variable number of arguments should use va_arg() to extract arguments from the variable argument list.
• For a function receives variable number of arguments it is necessary that the function should receive at least one fixed argument.
• In a function that receives variable number of arguments the fixed arguments passed to the function can be at the end of argument list.
• It is necessary to call the macro va_end if va_start is called in the function.
• Can we pass a variable argument list to a function at run-time?
• While defining a variable argument list function we drop the ellipsis(...)?
• Can we write a function that takes a variable argument list and passes the list to another function?
• Can the fixed arguments passed to the function that accepts variable argument list, occur at the end?
• Is it necessary that in a function which accepts variable argument list there should be at least be one fixed argument?