161) #define
assert(cond) if(!(cond)) \
(fprintf(stderr, "assertion failed: %s,
file %s, line %d \n",#cond,\
__FILE__,__LINE__), abort())
void main()
{
int i = 10;
if(i==0)
assert(i < 100);
else
printf("This statement becomes else
for if in assert macro");
}
Answer:
No
output
Explanation:
The else
part in which the printf is there becomes the else for if in the assert macro.
Hence nothing is printed.
The solution is to
use conditional operator instead of if statement,
#define
assert(cond) ((cond)?(0): (fprintf (stderr, "assertion failed: \ %s, file
%s, line %d \n",#cond, __FILE__,__LINE__), abort()))
Note:
However
this problem of “matching with nearest else” cannot be solved by the usual
method of placing the if statement inside a block like this,
#define
assert(cond) { \
if(!(cond))
\
(fprintf(stderr, "assertion failed: %s,
file %s, line %d \n",#cond,\
__FILE__,__LINE__), abort()) \
}
162) Is
the following code legal?
struct a
{
int
x;
struct a b;
}
Answer:
No
Explanation:
Is
it not legal for a structure to contain a member that is of the same
type as
in this case. Because this will cause the structure declaration to be recursive
without end.
163) Is
the following code legal?
struct a
{
int
x;
struct a *b;
}
Answer:
Yes.
Explanation:
*b is a
pointer to type struct a and so is legal. The compiler knows, the size of the
pointer to a structure even before the size of the structure
is
determined(as you know the pointer to any type is of same size). This type of
structures is known as ‘self-referencing’ structure.
164) Is
the following code legal?
typedef struct a
{
int
x;
aType *b;
}aType
Answer:
No
Explanation:
The typename
aType is not known at the point of declaring the structure (forward references
are not made for typedefs).
165) Is
the following code legal?
typedef struct a
aType;
struct a
{
int
x;
aType
*b;
};
Answer:
Yes
Explanation:
The
typename aType is known at the point of declaring the structure, because it is
already typedefined.
166) Is
the following code legal?
void main()
{
typedef
struct a aType;
aType
someVariable;
struct
a
{
int
x;
aType *b;
};
}
Answer:
No
Explanation:
When
the declaration,
typedef
struct a aType;
is
encountered body of struct a is not known. This is known as ‘incomplete types’.
167) void
main()
{
printf(“sizeof (void
*) = %d \n“, sizeof( void *));
printf(“sizeof
(int *) = %d \n”, sizeof(int *));
printf(“sizeof
(double *) = %d \n”, sizeof(double *));
printf(“sizeof(struct
unknown *) = %d \n”, sizeof(struct unknown *));
}
Answer :
sizeof
(void *) = 2
sizeof
(int *) = 2
sizeof
(double *) = 2
sizeof(struct
unknown *) = 2
Explanation:
The
pointer to any type is of same size.
168) char
inputString[100] = {0};
To get string input
from the keyboard which one of the following is better?
1) gets(inputString)
2) fgets(inputString,
sizeof(inputString), fp)
Answer &
Explanation:
The
second one is better because gets(inputString) doesn't know the size of the
string passed and so, if a very big input (here, more than 100 chars) the
charactes will be written past the input string. When fgets is used with stdin
performs the same operation as gets but is safe.
169) which
versions do you prefer of the following two,
1)
printf(“%s”,str); // or the more
curt one
2)
printf(str);
Answer &
Explanation:
Prefer
the first one. If the str contains any format characters like %d then it will
result in a subtle bug.
170) void
main()
{
int
i=10, j=2;
int
*ip= &i, *jp = &j;
int
k = *ip/*jp;
printf(“%d”,k);
}
Answer:
Compiler
Error: “Unexpected end of file in comment started in line 5”.
Explanation:
The
programmer intended to divide two integers, but by the “maximum munch” rule,
the compiler treats the operator sequence / and * as /* which happens to be the
starting of comment. To force what is intended by the programmer,
int
k = *ip/ *jp;
//
give space explicity separating / and *
//or
int
k = *ip/(*jp);
//
put braces to force the intention
will
solve the problem. 
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