Enum initializer as const - vala

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).