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Can you write a code which compiles in C but not in C++ ?
This question puzzles many who believe that C++ is a superset of C language, and all C language code is valid in C++. But it is not true and you should read the differences between C and C++ to know how they are different.Below are few examples which compiles in C and would fail to compile in C++:
Example 1:
This will not compile under C++ because class is a keyword, but will compile in C without any problems. Similarly any keywords which are specific to C++ such as public, private, virtual, friend etc can be used as identifiers in C, but not in C++.
Example 2:
int fun()
{
//some code
}
int main()
{
fun(10,20);
}
{
//some code
}
int main()
{
fun(10,20);
}
This will fail to compile in C++, because in C++, the declaration of a function with no argument list is equivalent to declaring it as function with void parameter list. But in C language, it means a function with unspecified number of arguments and we can pass any number of arguments to this function in C.
Example 3:
#include<stdlib.h>
int main()
{
int *array=malloc(sizeof(int)*100);
}
int main()
{
int *array=malloc(sizeof(int)*100);
}
This is valid in C because a pointer of type void* can be assigned to any other pointer without cast, but this is not in valid C++ because will have to give an explicit cast to it as in:
int *array=(int*)malloc(sizeof(int)*100);
Example 4:
#include<stdio.h>
int main()
{
static int i=5;
if(i>0)
printf("%d\n",i);
else
{
i--;
main();
return 0;
}
}
int main()
{
static int i=5;
if(i>0)
printf("%d\n",i);
else
{
i--;
main();
return 0;
}
}
This code is valid in C because recursion of main function is legal in C language whereas it is illegal in C++ language.
For more such differences, read the article by David R. Tribble on Incompatibilities between ISO C and ISO C++∞.
Comments [Hide comments/form]
This will not compile under c++ but will compile in C
-- proxy.iiit.ac.in (2006-10-14 12:18:23)
for the second program when we pass the arguments how will it accept and calculate in c....
-- 221-134-208-203.sify.net (2007-07-31 13:15:27)
ya........ur question is right.Even I am having the same doubt.
-- 123.236.92.91 (2008-12-26 13:59:01)
Can we somehow get an access the stack addresses for these passed values since they reside on the stack on function being called?
-- cpe-76-185-58-5.tx.res.rr.com (2009-06-16 19:21:41)
That depends on your implementation. If you do find out a way to access them, your method would not apply for other compiler implementations because the C standard does not specify how the underlying storage is taken care of - stack/heap or whatever.
-- SharathAV
(2009-06-18 15:13:11)
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