feat: allow custom arguments for clang

Author: richerfu

README.md

@@ -128,6 +128,9 @@ The following variables affect the building the of the `opencv` crate, but belon
   `*.dll`s next to your binary. Be sure to specify paths in UNIX style (/C/Program Files/Dir) because colon
   in `PATH` might be interpreted as the entry separator. Summary [here](https://stackoverflow.com/a/6546427).
 
+* `OPENCV_CLANG_ARGS`
+  Allow custom arguments for generating and parsing code with clang, see the [documentation for clang arguments](https://docs.rs/clang/latest/clang/struct.Parser.html#method.arguments).
+
 * clang crate environment variables
   See crate's [README](https://github.com/KyleMayes/clang-sys/blob/master/README.md#environment-variables)
 

binding-generator/src/generator.rs

@@ -1,4 +1,5 @@
 use std::borrow::Cow;
+use std::env;
 use std::fs::File;
 use std::io::BufReader;
 use std::ops::ControlFlow;
@@ -433,6 +434,11 @@ impl Generator {
 		args.push("-includeocvrs_common.hpp".into());
 		// need to have c++14 here because VS headers contain features that require it
 		args.push("-std=c++14".into());
+		// allow us to use some custom clang args
+		let clang_args = env::var_os("OPENCV_CLANG_ARGS").unwrap_or_default();
+		clang_args.to_string_lossy().split_whitespace().map(String::from).for_each(|i| {
+			args.push(i.into());
+		});
 		args
 	}