[nicl] RFR: Support UnexposedDecl

[Henry Jen]

Hi,

C allows K&R style function declaration, although is obsolete. Such declaration is considered non-prototype function declaration. Compile with -Wstrict-prototypes in clang will emit warnings.

However, many C++ code when providing C binding will use this form instead of int func(void) because that’s exactly what it should be in C++ and -Wstrict-prototypes for C is off by default.

So, consider following C header file which is actually quite often from C++ developer, who may consider writing int func(void) redundant,

#ifdef __cplusplus
extern “C” {
#endif

int func();

#ifdef __cplusplus
}
#endif

jextract will need to deal with that situation. With proposed webrev[1], developer can run jextract with C++ mode by passing ‘-C -x -C c++’, this is essential forcing libclang to parse header using c++ syntax. This is not too bad as eventually we will support c++, but there could be unexpected side-effects as jextract cannot deal with all c++ syntax yet. However, this is no worse than using jextract against a .hpp file.

When running in c++ mode, the extern “C” would be a UnexposedDecl, the webrev add support for that.

[1] http://cr.openjdk.java.net/~henryjen/panama/namespace/webrev/

I would like to propose additional follow up by adding a switch —noKR(name is up to discussion). Developer can use that switch if he is certain the header file is not using K&R style prototype. In this case, we simply consider all non-prototype function declaration as no argument function prototype. Then we still parsing use C mode which should be less surprising. What do you think?

The change is made for nicl branch, I will port into foreign branch later with a couple other fixes for nicl in queue.

Cheers,
Henry