fix: support header_contents in macro fallback

Author: zRedShift

bindgen-tests/tests/tests.rs

@@ -617,6 +617,37 @@ fn test_macro_fallback_non_system_dir() {
     }
 }
 
+#[test]
+fn test_macro_fallback_header_contents() {
+    if let Some((9, _)) = clang_version().parsed {
+        return;
+    }
+
+    let tmpdir = tempfile::tempdir().unwrap();
+    let actual = builder()
+        .disable_header_comment()
+        .header_contents(
+            "test.h",
+            "#define UINT32_C(c) c ## U\n\
+             #define SIMPLE 42\n\
+             #define COMPOUND UINT32_C(69)\n",
+        )
+        .clang_macro_fallback()
+        .clang_macro_fallback_build_dir(tmpdir.path())
+        .clang_arg("--target=x86_64-unknown-linux")
+        .generate()
+        .unwrap()
+        .to_string();
+
+    let actual = format_code(actual).unwrap();
+    let expected = format_code(
+        "pub const SIMPLE: u32 = 42;\npub const COMPOUND: u32 = 69;\n",
+    )
+    .unwrap();
+
+    assert_eq!(expected, actual);
+}
+
 #[test]
 // Doesn't support executing sh file on Windows.
 // We may want to implement it in Rust so that we support all systems.

bindgen/clang.rs

@@ -1915,6 +1915,7 @@ impl Drop for TranslationUnit {
 pub(crate) struct FallbackTranslationUnit {
     file_path: String,
     pch_path: String,
+    materialized_headers: Vec<String>,
     idx: Box<Index>,
     tu: TranslationUnit,
 }
@@ -1931,6 +1932,7 @@ impl FallbackTranslationUnit {
         file: String,
         pch_path: String,
         c_args: &[Box<str>],
+        materialized_headers: Vec<String>,
     ) -> Option<Self> {
         // Create empty file
         OpenOptions::new()
@@ -1951,6 +1953,7 @@ impl FallbackTranslationUnit {
         Some(FallbackTranslationUnit {
             file_path: file,
             pch_path,
+            materialized_headers,
             tu: f_translation_unit,
             idx: f_index,
         })
@@ -1989,6 +1992,9 @@ impl Drop for FallbackTranslationUnit {
     fn drop(&mut self) {
         let _ = std::fs::remove_file(&self.file_path);
         let _ = std::fs::remove_file(&self.pch_path);
+        for path in &self.materialized_headers {
+            let _ = std::fs::remove_file(path);
+        }
     }
 }
 

bindgen/ir/context.rs

@@ -2055,11 +2055,46 @@ If you encounter an error missing from this list, please file an issue or a PR!"
 
             let index = clang::Index::new(false, false);
 
+            let build_dir =
+                match self.options().clang_macro_fallback_build_dir {
+                    Some(ref path) => path.as_os_str().to_str()?,
+                    None => ".",
+                };
+            let materialized_headers: Vec<String> = self
+                .options()
+                .input_header_contents
+                .iter()
+                .enumerate()
+                .map(|(index, (_, contents))| {
+                    let path =
+                        format!("{build_dir}/.macro_eval_header_{index}.h");
+                    std::fs::write(&path, contents.as_ref()).unwrap_or_else(
+                        |error| {
+                            panic!(
+                                "failed to materialize header_contents() for \
+                                 clang_macro_fallback at {path}: {error}"
+                            )
+                        },
+                    );
+                    path
+                })
+                .collect();
+
+            let effective_headers: Vec<Box<str>> = self
+                .options()
+                .input_headers
+                .iter()
+                .cloned()
+                .chain(materialized_headers.iter().map(|path| {
+                    path.as_str().into()
+                }))
+                .collect();
+
             let mut header_names_to_compile = Vec::new();
             let mut header_paths = Vec::new();
             let mut header_includes = Vec::new();
             let [input_headers @ .., single_header] =
-                &self.options().input_headers[..]
+                &effective_headers[..]
             else {
                 return None;
             };
@@ -2121,8 +2156,12 @@ If you encounter an error missing from this list, please file an issue or a PR!"
                     c_args.push(arg.clone());
                 }
             }
-            self.fallback_tu =
-                Some(clang::FallbackTranslationUnit::new(file, pch, &c_args)?);
+            self.fallback_tu = Some(clang::FallbackTranslationUnit::new(
+                file,
+                pch,
+                &c_args,
+                materialized_headers,
+            )?);
         }
 
         self.fallback_tu.as_mut()

bindgen/lib.rs

@@ -361,13 +361,14 @@ impl Builder {
                 .flat_map(|header| ["-include".into(), header.clone()]),
         );
 
-        let input_unsaved_files =
-            std::mem::take(&mut self.options.input_header_contents)
-                .into_iter()
-                .map(|(name, contents)| {
-                    clang::UnsavedFile::new(name.as_ref(), contents.as_ref())
-                })
-                .collect::<Vec<_>>();
+        let input_unsaved_files = self
+            .options
+            .input_header_contents
+            .iter()
+            .map(|(name, contents)| {
+                clang::UnsavedFile::new(name.as_ref(), contents.as_ref())
+            })
+            .collect::<Vec<_>>();
 
         Bindings::generate(self.options, &input_unsaved_files)
     }