Enum initializer as const

Question

Are vala enums not integer based? This example generates a "c" compile error. Not a big deal, but would like to understand why.

const int INT_UNINITIALIZED = 999;
public enum ScopeTypes {
    /*OSS:Fix:GLib requires a default value, set GLOBALS = 0
     (VSCodeDbgSvr.exe:31979): GLib-GObject-CRITICAL **: g_param_spec_enum: assertion 'g_enum_get_value (enum_class, default_value) != NULL' failed*/
    NONE = INT_UNINITIALIZED,
    GLOBALS = 0,
    ARGUMENTS,
    LOCALS,
    EXCEPTIONS,
    TOT_SCOPE_TYPES;
    //Vala enums may have methods:
    public bool is_global() {
        return (this == GLOBALS || this == EXCEPTIONS);
        }
    public bool is_function() {
        return (this == ARGUMENTS || this == LOCALS);
        }
    public bool is_valid() {
        return (this != NONE);
        }
    }

The compile output:

    > Executing task: /opt/vala/bin/valac helloworld.vala class1.vala --pkg libvala-0.40 -X -I/opt/vala/include/vala-0.40 -X -O0 --vapidir=/opt/vala/share/vala/vapi --debug --save-temps -o helloworld.exe <

   /media/george/SharedData/Projects/Vala/Examples/playground-2/helloworld.c:82:21: error: ‘INT_UNINITIALIZED’ undeclared here (not in a function)
      SCOPE_TYPES_NONE = INT_UNINITIALIZED,
                         ^~~~~~~~~~~~~~~~~
    error: cc exited with status 256
    Compilation failed: 1 error(s), 1 warning(s)
    The terminal process terminated with exit code: 1

Answer 1

The relevant part of the error message is:

error: ‘INT_UNINITIALIZED’ undeclared here (not in a function)

The C compiler is complaining that it can not find the declaration of your constant. So it is not a type problem at all.

It is a scope / ordering problem.

If you compile the code with valac -C you get a .c file that looks something like this:

typedef enum  {
        SCOPE_TYPES_NONE = INT_UNINITIALIZED,
        SCOPE_TYPES_GLOBALS = 0,
        SCOPE_TYPES_ARGUMENTS,
        SCOPE_TYPES_LOCALS,
        SCOPE_TYPES_EXCEPTIONS,
        SCOPE_TYPES_TOT_SCOPE_TYPES
} ScopeTypes;



#define INT_UNINITIALIZED 999

Note how the Vala compiler has reordered the code to declare the enum first and the constant later.

Since in C the order of declarations in a file is important this can not compile.

I would consider this to be a compiler bug and you may want to report this to the GNOME bugtracker (product Vala).