ENUM types and usage in c and c++

Question

if I wrote like this:

typedef enum {
  foo_1,
  foo_2
}foo ;

I found that I can use

int footype = foo::foo_1 in c++

and I can directly use

int footype = foo_1 in c,

so is there a way that can write same code that works both in c++ and c? the code is inside one header file with only one structure.

Just use foo_1 without the namespace, it should work in both, althougt you have to declare using namespace foo for c++ — dinox0r
– dinox0r, Commented Nov 7, 2012 at 15:15
@h3nr1x foo is not a namespace and no need to declare it in C++. — SomeWittyUsername
– SomeWittyUsername, Commented Nov 7, 2012 at 15:16
@icepack yes, you're right, I missreaded the question and obviated the foo after the typedef, sorry — dinox0r
– dinox0r, Commented Nov 7, 2012 at 18:09

Praetorian · Accepted Answer · 2012-11-07 15:16:55Z

6

int footype = foo_1;

That will compile in both C and C++.

int footype = foo::foo_1;

This syntax is only necessary for C++11's strongly typed enums.

answered Nov 7, 2012 at 15:16

Praetorian

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Comments

Armen Tsirunyan · Accepted Answer · 2012-11-07 15:16:10Z

4

This

int footype = foo::foo_1

is legal only in C++11. In C++03 an enumeration is not a scope and this is illegal, just like in C. In C++11 there are two types of enums - ordinary C-like enums, and scoped enums, declared with

 enum class

For the latter, the enumerator qualification(::) is mandatory. For the former - optional.

So, using simply

int footype foo = foo_1;

will work in all C, C++03 and C++11

answered Nov 7, 2012 at 15:16

Armen Tsirunyan

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1 Comment

Dietrich Epp Over a year ago

It looks suspiciously like you didn't read the question... this is about writing code that is compatible with C and C++ (for use in header files).

user442585 · Accepted Answer · 2012-11-07 15:18:02Z

1

If you are OK with dropping the typedef it should "just work"

enum {
    foo_1,
    foo_2
};

int
main(void)
{
    int foo = foo_1;

    return 0;
}

That compiles for me with both gcc and g++

g++ --std=c++03 enum.cc -o enum_cpp
gcc --std=c99 enum.c -o enum_c

answered Nov 7, 2012 at 15:18

user442585

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2 Comments

Praetorian Over a year ago

Having the typedef there is not an issue

Paul R Over a year ago

Make it gcc -Wall .../g++ -Wall ....

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