Improve macro defined constants to recognize #define CONSTANT ((int) 1)

[azerupi]

In the header files I am trying to make bindings for, some constants are defined like this:

#define kOfxStatFailed  ((int)1)
#define kOfxStatErrFatal ((int)2)
// ...

Can this pattern be supported? Maybe I can attempt to add this if I get some guidance :)

[emilio]

This can certainly be supported, though it'd be kind of a one-off.

Indeed I think this eventually worked (by chance) because at one point we tried to find just the first integer literal token.

I think the best approach for this is something like:

• Stripping parentheses of the cexpr_tokens variable in src/ir/var.rs.
• Try to split a leading cast on those tokens (something like: First one is punctuation and the character b'(', next token is a literal and a well known type (let's support only int to begin with, for example), and then another punctuation with the b')' char.
• With that stripped, the rest of the code should just work. Also, we can detect what the cast is, and save it to generate the correct type, that'd be a plus :)

Do you want to try implementing it? I'm not sure I'll find the time myself in the near term. If you want, happy to elaborate more if needed :)

[azerupi]

Yes, I will give it a try :)
I'll let you know if I get stuck.

[nox]

Can't we just make cexpr support casts?

[azerupi]

I think it would be better too. The code I wrote felt out of place and it would be better to handle all macro const stuff in the same place.

[emilio]

Yeah, that'd work better. I've also just realized we can't just strip wrapping parentheses since they can change the precedence of operators.

[bbigras]

I have a similar case. Anyone knows how I can use the following in Rust in the meantime?

#define GSS_C_NO_NAME ((gss_name_t) 0)
#define GSS_C_NO_BUFFER ((gss_buffer_t) 0)

[emilio]

I guess you'd need to define them manually :/

[fitzgen]

@BrunoQC if gss_foo_t are typedefs of pointers, then this should work:

0 as *mut _

If they are typedefs of some kind of integer type, then this should work:

0 as _

Otherwise, you'll need to use std::mem::transmute (maybe with lazy_static if you want it to be a global):

use std::mem;

let no_name: gss_name_t = unsafe { mem::transmute(0) };

[target-san]

I have a rather stupid idea. Which can 'shoot' tho.
For each macro definition, construct a stub C++ file

#include "source_header.h"
const auto CONSTANT = MACRO;

Then force CLang to process it and give type and value of CONSTANT. If it doesn't compile, then it's not a macro constant.
It may be rather slow - but I'd presonally wait once to have proper constants.

[ristew]

I imagine the following could never work with this
#define ECL_T ((cl_object)(cl_symbols+1))
where cl_symbols is an array holding structs.