Check if bool is defined in mixed C/C++

Question

So I'm having issues with some code that I've inherited. This code was building fine in a C-only environment, but now I need to use C++ to call this code. The header `problem.h` contains: ``` #ifndef _BOOL typedef unsigned char bool; static const bool False = 0; static const bool True = 1; #endif struct astruct { bool myvar; /* and a bunch more */ } ``` When I compile it as C++ code, I get `error C2632: 'char' followed by 'bool' is illegal` I get the same error if I wrap the `#include "problem.h"` in `extern "C" { ... }` (which I don't understand, because there should be no keyword `bool` when compiling as C?) I tried removing the block from `#ifndef _BOOL` to `#endif`, and compiling as C++, and I get errors: `error C2061: C requires that a struct or union has at least one member` `error C2061: syntax error: identifier 'bool'` I just don't understand how the C++ compiler is complaining about a redefinition of `bool`, yet when I remove the redefinition and try to just use `bool` to def…

Accepted Answer

Because `bool` is a basic type in C++ (but not in C), and can't be redefined.

You can surround your code with

```
#ifndef __cplusplus
typedef unsigned char bool;
static const bool False = 0;
static const bool True = 1;
#endif
```

Check if bool is defined in mixed C/C++

Solution

Problem