Handle gdb command failure gracefully in compiletest

Previously, if the gdb command was available, but threw an error, compiletest would panic.  This is obviously not good. Now, gdb is treated as missing if calling `gdb --version` does not output anything on stdout.

diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index e3d453a991d802d3e23dbc5717ee4cc6cedbeba0..304143eaa0bfffcd32ea7c10e1303791786a9ca1 100644 (file)
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -736,17 +736,12 @@ fn analyze_gdb(gdb: Option<String>) -> (Option<String>, Option<u32>, bool) {
         Some(ref s) => s,
     };
 
-    let version_line = Command::new(gdb)
-        .arg("--version")
-        .output()
-        .map(|output| {
-            String::from_utf8_lossy(&output.stdout)
-                .lines()
-                .next()
-                .unwrap()
-                .to_string()
-        })
-        .ok();
+    let mut version_line = None;
+    if let Ok(output) = Command::new(gdb).arg("--version").output() {
+        if let Some(first_line) = String::from_utf8_lossy(&output.stdout).lines().next() {
+            version_line = Some(first_line.to_string());
+        }
+    }
 
     let version = match version_line {
         Some(line) => extract_gdb_version(&line),