C doesn't have a bool? Also VS2010 question

Question

I'm using VS 2010 Pro.

First, C doesn't have a bool type? I just have to use int with 0/1. Seems odd as most languages consider boolean a standard type.

Also I have Visual Studio 2010 Pro but doesn't have a "C Project". I just created an Empty C++ Project. The file names end with .c

The problem with this is the keywords are messed up (shows bool as highlighted/valid in the editor, but compiler doesn't like it).

I went to repair/add components and they have C#, F#, C++, Visual Basic; but no C?

Answer 1

Newest C standard (C99) has bool type indeed. Just include stdbool.h and you can use it. Unfortunately MSVC does not haver proper support for C at all. Only partial C89.

Answer 2

The current C language (C99) has a bool type (actually _Bool, but including stdbool.h declares a typedef alias bool for it), but since you're using MSVC, that's not available to you. In any case, using boolean types in C is completely non-idiomatic and largely useless. Just use int like everyone else. Or if you need a giant array of them, make your own bit-array implementation.

Answer 3

C did not have an actual Boolean type until C99.

As a result, idiomatic C doesn't really use boolean-valued symbols or expressions as such (i.e., you won't see many explicit tests against "true" or "false"). Instead, any zero-valued integral expression or a NULL pointer will evaluate to "false", and any non-zero-valued integral expression or a non-NULL pointer will evaluate to "true". So you'll see a lot of code like:

foo *bar = malloc(sizeof *bar * ...);
if (bar) // equivalent to writing bar != NULL
{
   // bar is non-NULL
} 

Relational and equality expressions such as a == b or c < d will evaluate to an integral type with a value of either 1 (true) or 0 (false).

Some people introduce their own TRUE or FALSE symbolic constants by doing something like

#define TRUE  (1)  // or (!FALSE), or (1==1), or...
#define FALSE (0)  // or (!TRUE), or (1==0), or ...

Unforunately, some of those people occasionally manage to misspell 0 or 1 (or the expressions that are supposed to evaluate to 0 or 1); I once spent an afternoon chasing my tail because someone screwed up and dropped a header where TRUE == FALSE.

Not coincidentally, that was the day I stopped using symbolic constants for Boolean values altogether.

Answer 4

See R.'s answer for information about the bool type.

Unfortunately, MSVC doesn't support C99 when it's compiling C code - it has bits and pieces (generally things in the C99 library that are required by C++), but for the most part it only supports C90.

As for bool still being highlighted in the editor - the highlighting in MSVC may be sophisticated, but it doesn't take into account the differentiation between C, C++, and C++/CLI. For example, if you use a construct that's CLI-only, it'll be highlighted as such even if your project has nothing to do with CLI.