C++ | C incompatibilities

This describes what C code will break in a C++ compiler.

Reserved Keywords

The first example are keywords that have a special purpose in C++: the following is legal in C, but not C++.

int class = 5

These errors are easy to fix: just rename the variable.

Weakly typed pointers

In C, pointers can be cast to a void*, which needs an explicit cast in C++. The following is illegal in C++, but legal in C:

void* ptr;
int* intptr = ptr;

Adding an explicit cast makes this work, but can cause further issues.

goto or switch

In C++, you may not skip initializations with goto or switch. The following is valid in C, but not C++:

goto foo;
int skipped = 1;
foo;

These bugs may require redesign.