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C Interview Questions and Answers

Ques. Will the following program execute?
void main()
void *vptr = (void *) malloc(sizeof(void));

It will throw an error, as arithmetic operations cannot be performed on void pointers.

It will not build as sizeof cannot be applied to void* ( error ?Unknown size? )

How can it execute if it won?t even compile? It needs to be int main, not void main. Also, cannot increment a void *.

According to gcc compiler it won?t show any error, simply it executes. but in general we can?t do arthematic operation on void, and gives size of void as 1

The program compiles in GNU C while giving a warning for ?void main?. The program runs without a crash. sizeof(void) is ?1? hence when vptr++, the address is incremented by 1.

Regarding arguments about GCC, be aware that this is a C++ question, not C. So gcc will compile and execute, g++ cannot. g++ complains that the return type cannot be void and the argument of sizeof() cannot be void. It also reports that ISO C++ forbids incrementing a pointer of type ?void*?.

in C++
voidp.c: In function `int main()?:
voidp.c:4: error: invalid application of `sizeof? to a void type
voidp.c:4: error: `malloc? undeclared (first use this function)
voidp.c:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
voidp.c:6: error: ISO C++ forbids incrementing a pointer of type `void*?

But in c, it work without problems

void main()
char *cptr = 0?2000;
long *lptr = 0?2000;
printf(? %x %x?, cptr, lptr);
Will it execute or not?

For Q2: As above, won?t compile because main must return int. Also, 02000 cannot be implicitly converted to a pointer (I assume you meant 02000 and not 0?2000.)

Not Excute.
Compile with VC7 results following errors:
error C2440: ?initializing? : cannot convert from ?int? to ?char *?
error C2440: ?initializing? : cannot convert from ?int? to ?long *?

Not Excute if it is C++, but Excute in C.
The printout:
2001 2004

In C++
[$]> g++ point.c
point.c: In function `int main()?:
point.c:4: error: invalid conversion from `int? to `char*?
point.c:5: error: invalid conversion from `int? to `long int*?

in C
[$] etc > gcc point.c
point.c: In function `main?:
point.c:4: warning: initialization makes pointer from integer without a cast
point.c:5: warning: initialization makes pointer from integer without a cast
[$] etc > ./a.exe
2001 2004
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