xcode - Convert Objective-C enum constants to string names

Question

Previously, this was impossible (you have to write it all out by hand / create a static array / put all the values into a dictionary and read them back ... etc)

But I've noticed that the latest Xcode's lldb (4.6, maybe earlier versions too) is automatically converting enum-constants to strings.

My problem is that we use a lot of libraries - including Apple's own! - which use annoying public enums with no "value-to-string" method offered. So I end up having to (many, many times over) do the "well, since Mr. Library Author didn't do this, now I have to make the static array for them...".

I kept hoping Apple would provide a way out of this - is it finally here? Or is this some trick that only the debugger can do - mere runtime code has no access to it?

Answer 1

lldb doesn't have any special capabilities regarding printing enum names. I think what you're seeing is the result of the enum values being recorded in the debug info (or not). For instance,

enum myenums {a = 0, b, c};
int main ()
{
 enum myenums var = b;
 return (int) var;  // break here
}

% xcrun clang -g a.c
% xcrun lldb a.out
(lldb) br s -p break
Breakpoint 1: where = a.out`main + 18 at a.c:5, address = 0x0000000100000f92
(lldb) r
[...]
-> 5     return (int) var;  // break here
   6    }
(lldb) p var
(myenums) $0 = b
(lldb) p (myenums) 0
(myenums) $1 = a
(lldb) 

If you look at the debug info for this binary (dwarfdump a.out.dSYM) you'll see that the variable var's type is myenums and the debug information includes the values of those enumerated types:

0x0000005a:     TAG_enumeration_type [5] *
                 AT_name( "myenums" )
                 AT_byte_size( 0x04 )
                 AT_decl_file( "/private/tmp/a.c" )
                 AT_decl_line( 1 )

0x00000062:         TAG_enumerator [6]  
                     AT_name( "a" )
                     AT_const_value( 0x0000000000000000 )

0x00000068:         TAG_enumerator [6]  
                     AT_name( "b" )
                     AT_const_value( 0x0000000000000001 )

0x0000006e:         TAG_enumerator [6]  
                     AT_name( "c" )
                     AT_const_value( 0x0000000000000002 )

If I add another enum to my sample file which isn't used anywhere,

enum myenums {a = 0, b, c};
enum otherenums {d = 0, e, f}; // unused in this CU
int main ()
{
 enum myenums var = b;
 return (int) var;  // break here
}

re-compile and look at the DWARF again via dwarfdump, I won't find any debug info describing otherenums - it is unused (in this compilation unit) and so it is elided.