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Write a C program that won’t compile in C++
Here, we will write some c programs that won’t compile in c++. Though c++ is considered as a successor of c that has all its features and has compatibility with c code there are some programs that won’t compiler or given a compilation error when compiled with c++ compiler.
A list of some of the C programs that won’t compile in c++ are −
Call to a function before declaration − In c++, function call before declaration gives compilation error. But this works fine in c.
Example
#include <stdio.h>
int main(){
printHello();
return 0;
}
void printHello(){
printf("TutorialsPoint");
}Output
TutorialsPoint
Using typecasted pointers − if we declare a pointer in c as void and then use this pointer to point other data variables. This can be done in c by the compiler itself but in c++, these pointers need to be typecasted.
Example
#include <stdio.h>
int main(){
void *ptr;
int *ptr2 = ptr;
return 0;
}Declaring constant values without initialising − in c, you can declare constant values without providing any value to it but this returns an error when done in c++.
Example
#include <stdio.h>
int main(){
const int x;
printf("%d", x);
return 0;
}Output
0
Using normal pointer with const variable − in c++ this is not allowed while c allows the use of const variable with a normal pointer.
Example
#include <stdio.h>
int main(void){
int const x = 3424;
int *cptr = &x;
printf("value of pointer : %d\n", *cptr);
return 0;
}Output
Value of pointer: 3424
Using specific keywords as variable names − In c programming language use of certain keywords as variable names is valid i.e. would compile in c but won’t compile in c++.
Example
#include <stdio.h>
int main(void){
int class = 5;
printf("%d", class);
}Output
5
These are those keywords that are included in c++, some more are new, delete, explicit, etc.
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