Capture and log stderr on build failure

Author: jdub

libbindgen/tests/tests.rs

@@ -6,10 +6,10 @@ use std::env;
 use std::fs;
 use std::io::{BufReader, BufRead, Read, Write};
 use std::path::{Path, PathBuf};
-use std::process::{Command, ExitStatus};
+use std::process::Command;
 use tempdir::TempDir;
 
-fn test_generated_bindings(header: &PathBuf, output: &str) -> Result<ExitStatus, std::io::Error> {
+fn test_generated_bindings(header: &PathBuf, output: &str) -> Result<(), ()> {
     let temp_dir = TempDir::new("bindgen-tests")
         .expect("Couldn't create temp dir");
 
@@ -25,14 +25,24 @@ fn test_generated_bindings(header: &PathBuf, output: &str) -> Result<ExitStatus,
     binary.set_extension("bin");
 
     let mut file = fs::File::create(&source).expect("Couldn't create output source file");
-    try!(file.write_all(output.as_bytes()));
+    file.write_all(output.as_bytes()).expect("Couldn't write to output source file");
 
-    Command::new("rustc")
+    let output = Command::new("rustc")
         .arg("--test")
-        .arg(source)
+        .arg(&source)
         .arg("-o")
         .arg(binary)
-        .status()
+        .output();
+    
+    match output {
+        Ok(o) => if o.status.success() {
+            Ok(())
+        } else {
+            println!("Failed to build {:?}:\n{}", source, String::from_utf8(o.stderr).unwrap());
+            Err(())
+        },
+        Err(_) => Err(()),
+    }
 }
 
 fn spawn_bindgen(header: &PathBuf, builder: libbindgen::Builder) -> Result<(), ()> {
@@ -58,7 +68,7 @@ fn spawn_bindgen(header: &PathBuf, builder: libbindgen::Builder) -> Result<(), (
         .expect("Couldn't read from expected test output");
 
     if output == buffer {
-        test_generated_bindings(&header, &output).and(Ok(())).or(Err(()))
+        test_generated_bindings(&header, &output)
     } else {
         println!("diff expected generated\n--- expected: {:?}\n+++ generated from: {:?}",
             expected, header);