Document providing include paths and FAQ for missing system headers

[vks]

Sometimes there is a cryptic fatal error: 'stddef.h' file not found, presumabely when libclang is incorrectly configured:

servo/gecko-media#71
rsmpi/rsmpi#1
#242
ajtulloch/caffe.rs#1

In the past, this issue was fixed by making sure to install the clang package or by finding the missing pathes and adding them to the includes.

I was wondering whether bindgen could work around this issue? (The second solution above can be automated.) Alternatively, it could be documented how to fix it.

[emilio]

This is probably better suited for https://github.com/KyleMayes/clang-sys. That's the crate bindgen uses for figuring out system headers.

I agree that if this is a common problem, it'd be nice to document it, though.

Thanks for the report :)

[fitzgen]

For the most part, bindgen is not in the include-path-wrangling game, and we leave that to libclang. It's full of tricky edge cases and system specific bits, and at least C compilers and their behavior are largely a known quantity, even if not always the most transparent.

I would love to merge some PRs adding more documentation / FAQs about this stuff though!

[Imirsen]

I was experiencing this issue on Ubuntu 17.10 compiling a simple C file including stddef.h. I investigated and was able to fix it by making bindgen pass the C search paths to the driver when it detects that it is compiling C. See pull request #1351

[virtualritz]

I have the 'stddef.hI' issue. I'm on macOS 10.13.6, latest command line tools installed.
When trying to generate any C++ bindings through bindgen I get:

/Library/Developer/CommandLineTools/usr/include/c++/v1/cstddef:44:15: fatal error: 'stddef.h' file not found
/Library/Developer/CommandLineTools/usr/include/c++/v1/cstddef:44:15: fatal error: 'stddef.h' file not found, err: true
thread 'main' panicked at 'Unable to generate 3Delight bindings: ()', libcore/result.rs:1009:5

Generating C bindings works fine. I tried with several different C++ headers as input for bindgen. I always get this error.
The supposedly missing header is present on my system in many locations:

$ locate stddef.h
/Library/Developer/CommandLineTools/Library/PrivateFrameworks/LLDB.framework/Versions/A/Resources/Clang/include/stddef.h
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Kernel.framework/Versions/A/Headers/stddef.h
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stddef.h
/Library/Developer/CommandLineTools/usr/include/c++/v1/stddef.h
/Library/Developer/CommandLineTools/usr/lib/clang/10.0.0/include/stddef.h
/Library/Developer/CommandLineTools/usr/lib/tapi/10.0.0/include/stddef.h
/System/Library/Frameworks/Kernel.framework/Versions/A/Headers/stddef.h
/System/Library/Frameworks/OpenCL.framework/Versions/A/lib/clang/2.0/include/stddef.h
/System/Library/PrivateFrameworks/GPUCompiler.framework/Versions/A/Libraries/lib/clang/3.5/include/stddef.h
/usr/include/stddef.h
/usr/local/Cellar/boost/1.67.0_1/include/boost/asio/detail/cstddef.hpp

bindgen 0.41.0
rustc 1.30.0-nightly (ae7fe84e8 2018-09-26)
Apple LLVM version 10.0.0 (clang-1000.10.44.2)

I tried adding some (and even all) of the above paths as clang args in build.rs but the issue remains.

[bbqsrc]

Is there a known solution to this problem?

[emilio]

Each problem is generally different depending on the setup. Could you file a separate issue pointing out which libclang are you using, and the first few lines of running bindgen with RUST_LOG=debug?

[virtualritz]

I have not managed to find a solution for this. It's basically the reason why bindgen is useless for me on macOS for certain projects that depend on system headers.
Even if there are multiple ailments – depending on setup –, could they be documented somewhere, please?

[BusyJay]

Although it may not be rust-bindgen's problem, but it hurts user experiences of rust-bindgen badly. Hope to find a way to fix it permanently.

[psporysz]

I had similar problem when building Firefox codebase and the solution was to point auto-tools script to clang installed in CommandLineTools:

--with-clang-path=/Library/Developer/CommandLineTools/usr/bin/clang
--with-libclang-path=/Library/Developer/CommandLineTools/usr/lib/

Not sure how to set this up in rust world thus i did something ugly:

sudo installer -pkg /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg -target /

The above "fix" is just work-around for impatient souls who ended up here and do not know rust and mac ecosystem well enough ;)