C code with macros

[sindhu sweet]

Hi ,all

#define MAX(x,y) ((x)>(y)?(x):(y)
main()
{
intx=5,y=5;
printf("maximum is %d",MAX(++x,++y));
}

this is a code using macros....
the output for this code is 6
is my answer right...

i hav a little bit confusion whether the maximum will be 6 or 5...
please clear my confusion..

Thanks in advance....

[weaknessforcats]

The macro expands to:

 ((++x)>(++y)?(++x):(++y)
 

x and y are altered multiple times before the end of the statement (called a sequence point). Changing a variable more than once within a given sequence point produces indeterminate results.

Therefore, any answer may be expected.

[suresh gani]

Hey max value will increment two times so take a close look at the code by replacing the macro call by its body

[sindhu sweet]

ok....i will try some more codes with macros..

[pradesah]

Answer I think is 7.
Because the result i.e ++y will be calculated twice.
Once during the comparision (++x > ++Y) and again during answering.
++x : ++y.
This sort of arguments should not be used in macros, as their answer cant be predicted easily and they may give unexpected results.

Thanks
Pradeep

[weaknessforcats]

Did anyone read my Post#2??

[JosAH]

Did anyone read my Post#2??

I did, but I wasn't participating in this thread ;-) You're right though: the OP should
be happy that no daemons flew out of his nose after doing such naughty deeds.

kind regards,

Jos

[RRick]

In this case, I think undefined means that no specific/single value can be expected. Are you going to get -23457898 as an answer? Probably not, but if you're expecting 7 you're going to be just as disappointed. What happens is compiler specific and that spells trouble.