Re: [PATCH RESEND v9 7/9] rust: add crate to expose bindings and interfaces

[Junjie Mao <junjie.mao@intel.com>]

On 8/31/2024 4:25 PM, Manos Pitsidianakis wrote:
> On Fri, 30 Aug 2024 14:03, Alex Bennée <alex.bennee@linaro.org> wrote:
> [.snip.]
>>
>> It is there:
>>
>>  /usr/lib/llvm-14/lib/clang/14.0.6/include/stdatomic.h
>>
>> in the search path:
>>
>>  clang -E -Wp,-v -
>>  clang -cc1 version 14.0.6 based upon LLVM 14.0.6 default target 
>> x86_64-pc-linux-gnu
>>  ignoring nonexistent directory 
>> "/usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../x86_64-linux-gnu/include"
>>  ignoring nonexistent directory "/include"
>>  #include "..." search starts here:
>>  #include <...> search starts here:
>>   /usr/lib/llvm-14/lib/clang/14.0.6/include
>>   /usr/local/include
>>   /usr/include/x86_64-linux-gnu
>>   /usr/include
>>  End of search list.
>>
>> but not in the list above. Have we told clang not to include system
>> search paths in the bindgen invocation?
> 
> stdatomic.h was first included in c11, and compilers already shipped the header 
> on their own (since they use builtin operations). The compiler header paths are 
> considered special system header paths by compilers, and what's happening here 
> is a bug in the manual searching logic in libclang like explained in the other 

Do you mean the manual searching logic in the *clang-sys* crate?

There is also a related issue [1] on GitHub.

[1] https://github.com/rust-lang/rust-bindgen/issues/2682

> replies. The bindgen invocation looks at system search paths otherwise, or it'd 
> fail to find headers used in QEMU.

Another approach to work around that issue is to define BOTH CLANG_PATH and 
LIBCLANG_PATH env vars, e.g., CLANG_PATH=/usr/bin/clang-13 
LIBCLANG_PATH=/lib/x86_64-linux-gnu/libclang-13.so. That works in my environment.

The following is a draft to do it in meson.build. It does NOT work yet as 
bindgen() does not allow customizing environment variables. I'm checking how to 
make it in meson.

diff --git a/meson.build b/meson.build
index 68d5b53684..1f6fc21f8d 100644
--- a/meson.build
+++ b/meson.build
@@ -3879,6 +3879,30 @@ if have_rust and have_system
      capture : true,
      check: true).stdout().strip().split()

+  host_clang = find_program(
+    'clang', version: '>=5.0.0',
+    required: true, native: true)
+  host_libclang = run_command(
+    host_clang,
+    '-print-file-name=libclang.so',
+    capture: true,
+    check: true).stdout().strip()
+  # Clang prints an absolute path when the library is found
+  if not host_libclang.startswith('/')
+    host_clang_major = host_clang.version().split('.')[0]
+    host_libclang = run_command(
+      host_clang,
+      '-print-file-name=libclang-' + host_clang_major + '.so',
+      capture: true,
+      check: true).stdout().strip()
+  endif
+  if not host_libclang.startswith('/')
+    error('Cannot find libclang.so for ' + host_clang.full_path())
+  endif
+  message('Found libclang: ' + host_libclang)
+
+  # TODO: set CLANG_PATH to host_clang.full_path() and LIBCLANG_PATH to
+  # host_libclang when invoking bindgen
    bindings_rs = import('rust').bindgen(
      input: 'rust/wrapper.h',
      dependencies: common_ss.all_dependencies(),