source: tests/except-mac.hfa@ d6b03b7

// Macros to try and make declaring and using exceptions easier
// No, these are not part of the language, they replace the virtual system.

// Internal use:
#define GLUE2(left, right) left##right
#define GLUE3(left, middle, right) left##middle##right

// The fully (perhaps overly) qualified name of the base exception type:
#define BASE_EXCEPT __cfaabi_ehm__base_exception_t

// Get the name of the vtable type and vtable instance for an exception type:
#define TABLE(name) GLUE2(name,_vtable)
#define INSTANCE(name) GLUE3(_,name,_vtable_instance)

// Throws and the bit of overhead:
#define THROW(expr) throw ((BASE_EXCEPT *)(expr))
#define THROW_RESUME(expr) throwResume ((BASE_EXCEPT *)(expr))



// The following macros are for defining your own new exception types.

// Declare vtable and forward declare the exception type and vtable instance.
// This should start a new exception declaration.
// ... argument is the additional vtable fields.
#define DECLARE_EXCEPT(except_name,parent_name,...) \
struct except_name; \
struct TABLE(except_name) { \
        struct TABLE(parent_name) const * parent; \
        size_t size; \
        void (*copy)(except_name *this, except_name * other); \
        void (*free)(except_name &this); \
        const char * (*msg)(except_name *this); \
        __VA_ARGS__ \
}; \
extern TABLE(except_name) INSTANCE(except_name);

// The first field of the exception structure should be created with this.
#define VTABLE_FIELD(except_name) \
struct TABLE(except_name) const * virtual_table

// In each constructor the vtable must be initialized.
#define VTABLE_INIT(this_name,except_name) \
this_name.virtual_table = &INSTANCE(except_name)

// Declare the vtable instance. This should end an exception declaration.
// ... argument is the remaining vtable field values.
#define VTABLE_INSTANCE(except_name,parent_name,copy,free,msg,...) \
TABLE(except_name) INSTANCE(except_name) @= { \
        &INSTANCE(parent_name), sizeof(except_name), \
        copy, free, msg, ## __VA_ARGS__ \
};

// Same, but used declarators for arguments.
#define VTABLE_INSTANCE_KEY(except_name,parent_name,copy,free,msg,...) \
TABLE(except_name) INSTANCE(except_name) @= { \
        .parent : &INSTANCE(parent_name), .size : sizeof(except_name), \
        .copy : copy, .free : free, .msg : msg, ## __VA_ARGS__ \
};



// Declare a trivial exception, one that adds no features:
#define TRIVIAL_EXCEPTION(name) \
DECLARE_EXCEPT(name,BASE_EXCEPT,) \
struct name { \
        VTABLE_FIELD(name); \
}; \
const char * GLUE2(name,_msg)(name * this) { \
    return #name; \
} \
void GLUE2(name,_copy)(name * this, name * other) { \
    this->virtual_table = other->virtual_table; \
} \
void ?{}(name & this) { \
        VTABLE_INIT(this,name); \
} \
VTABLE_INSTANCE(name,BASE_EXCEPT,GLUE2(name,_copy),^?{},GLUE2(name,_msg),)