Unable to generate bindings: ()

[helloqirun]

I am using this script https://gist.github.com/fitzgen/187381e358f60efa8194d0b276b4d11a.

The hashtag for my bindgen version is 4dd4ac7 .
The header file compiles with clang++ -std=c++11

$ ./b.sh bindgen abc.h

clang-4.0: warning: treating 'c-header' input as 'c++-header' when in C++ mode, this behavior is deprecated [-Wdeprecated]
abc.h:2:11: error: no member named 'c' in 'a<int>::(anonymous union at abc.h:3:3)'
abc.h:6:18: note: in instantiation of member function 'a<int>::a' requested here
abc.h:2:11: error: no member named 'c' in 'a<int>::(anonymous union at abc.h:3:3)', err: true
thread 'main' panicked at 'Unable to generate bindings: ()', /checkout/src/libcore/result.rs:860:4
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:60
             at /checkout/src/libstd/panicking.rs:380
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:396
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:611
   5: std::panicking::begin_panic_new
             at /checkout/src/libstd/panicking.rs:553
   6: std::panicking::begin_panic_fmt
             at /checkout/src/libstd/panicking.rs:521
   7: rust_begin_unwind
             at /checkout/src/libstd/panicking.rs:497
   8: core::panicking::panic_fmt
             at /checkout/src/libcore/panicking.rs:92
   9: core::result::unwrap_failed
             at /checkout/src/libcore/macros.rs:41
  10: <core::result::Result<T, E>>::expect
             at /checkout/src/libcore/result.rs:762
  11: bindgen::main::{{closure}}
             at src/main.rs:55
  12: std::panicking::try::do_call
             at /checkout/src/libstd/panicking.rs:479
  13: __rust_maybe_catch_panic
             at /checkout/src/libpanic_unwind/lib.rs:98
  14: std::panicking::try
             at /checkout/src/libstd/panicking.rs:458
  15: std::panic::catch_unwind
             at /checkout/src/libstd/panic.rs:361
  16: bindgen::main
             at src/main.rs:54
  17: __rust_maybe_catch_panic
             at /checkout/src/libpanic_unwind/lib.rs:98
  18: std::rt::lang_start
             at /checkout/src/libstd/panicking.rs:458
             at /checkout/src/libstd/panic.rs:361
             at /checkout/src/libstd/rt.rs:59
  19: main
  20: __libc_start_main
  21: _start
Interesting: bindgen failed to generate bindings for the test case!

$ cat abc.h

template <typename = int> struct a {
  a() { b.c; }
  union {
  } b;
};
a<> d() { return {}; }

[fitzgen]

@helloqirun thanks as always for another bug report :)

I have a question: are you passing the same flags to bindgen that you're passing to clang++? For example, this test case compiles with clang++ -std=++11; when you invoke bindgen, are you passing -std=c++11 as a clang flag?

These differences in clang++ vs libclang bugs are a bit of a conundrum, and there honestly isn't much we can do about them ourselves...

[helloqirun]

Hi Nick,

In your testing script, you invoke clang with

clang++ --std=c++14 -c

Do I need to remove the flag?

[fitzgen]

I guess it doesn't really matter as long as clang and bindgen get the same flags. If we're testing bindgen with -std=c++14, then we should also be comparing with clang++ -std=c++14, etc.

In the original bug report, you mentioned it compiles with clang++ -std=c++11 -- do you see the same behavior with -std=c++14 that we're using with bindgen?

[helloqirun]

Yes, indeed. Both clang++ and bindgen take the "std=c++14". The reported file also compiles with c++14. I just arbitrarily picked c++11 to demonstrate that it compiled. In your test script, I believe everything is c++14.