Require libclang 9.0 or newer

Adds a check for the loaded libclang version and returns an error
if the version is unsupported.

bindgen/lib.rs

@@ -65,6 +65,7 @@ use ir::item::Item;
 use options::BindgenOptions;
 use parse::ParseError;
 
+use clang_sys::Version;
 use std::borrow::Cow;
 use std::collections::hash_map::Entry;
 use std::env;
@@ -644,6 +645,8 @@ pub enum BindgenError {
     ClangDiagnostic(String),
     /// Code generation reported an error.
     Codegen(CodegenError),
+    /// Clang version is too old.
+    ClangTooOld(String),
 }
 
 impl std::fmt::Display for BindgenError {
@@ -664,6 +667,9 @@ impl std::fmt::Display for BindgenError {
             BindgenError::Codegen(err) => {
                 write!(f, "codegen error: {}", err)
             }
+            BindgenError::ClangTooOld(version) => {
+                write!(f, "clang is too old, loaded version: {}", version)
+            }
         }
     }
 }
@@ -744,6 +750,21 @@ impl Bindings {
     ) -> Result<Bindings, BindgenError> {
         ensure_libclang_is_loaded();
 
+        match clang_sys::get_library().unwrap().version() {
+            None => {
+                return Err(BindgenError::ClangTooOld(
+                    "3.4 or earlier".to_string(),
+                ))
+            }
+            Some(version) => {
+                if version < Version::V9_0 {
+                    return Err(BindgenError::ClangTooOld(format!(
+                        "{version:?}"
+                    )));
+                }
+            }
+        }
+
         #[cfg(feature = "runtime")]
         debug!(
             "Generating bindings, libclang at {}",

book/src/requirements.md

@@ -7,7 +7,7 @@ This page lists the requirements for running `bindgen` and how to get them.
 `bindgen` leverages `libclang` to preprocess, parse, and type check C and C++
 header files.
 
-It is required to use Clang 5.0 or greater.
+It is required to use Clang 9.0 or greater.
 
 ### Installing Clang