Add failing test of log statement during TLS dtors

Cargo.toml

@@ -34,6 +34,10 @@ harness = false
 name = "log-in-log"
 harness = false
 
+[[test]]
+name = "log_tls_dtors"
+harness = false
+
 [[test]]
 name = "init-twice-retains-filter"
 harness = false

tests/log_tls_dtors.rs

@@ -0,0 +1,66 @@
+#[macro_use]
+extern crate log;
+extern crate env_logger;
+
+use std::env;
+use std::process;
+use std::str;
+use std::thread;
+
+struct DropMe;
+
+impl Drop for DropMe {
+    fn drop(&mut self) {
+        debug!("Dropping now");
+    }
+}
+
+fn run() {
+    // Use multiple thread local values to increase the chance that our TLS
+    // value will get destroyed after the FORMATTER key in the library
+    thread_local! {
+        static DROP_ME_0: DropMe = DropMe;
+        static DROP_ME_1: DropMe = DropMe;
+        static DROP_ME_2: DropMe = DropMe;
+        static DROP_ME_3: DropMe = DropMe;
+        static DROP_ME_4: DropMe = DropMe;
+        static DROP_ME_5: DropMe = DropMe;
+        static DROP_ME_6: DropMe = DropMe;
+        static DROP_ME_7: DropMe = DropMe;
+        static DROP_ME_8: DropMe = DropMe;
+        static DROP_ME_9: DropMe = DropMe;
+    }
+    DROP_ME_0.with(|_| {});
+    DROP_ME_1.with(|_| {});
+    DROP_ME_2.with(|_| {});
+    DROP_ME_3.with(|_| {});
+    DROP_ME_4.with(|_| {});
+    DROP_ME_5.with(|_| {});
+    DROP_ME_6.with(|_| {});
+    DROP_ME_7.with(|_| {});
+    DROP_ME_8.with(|_| {});
+    DROP_ME_9.with(|_| {});
+}
+
+fn main() {
+    env_logger::init();
+    if env::var("YOU_ARE_TESTING_NOW").is_ok() {
+        // Run on a separate thread because TLS values on the main thread
+        // won't have their destructors run if pthread is used.
+        // https://doc.rust-lang.org/std/thread/struct.LocalKey.html#platform-specific-behavior
+        thread::spawn(run).join().unwrap();
+    } else {
+        let exe = env::current_exe().unwrap();
+        let out = process::Command::new(exe)
+            .env("YOU_ARE_TESTING_NOW", "1")
+            .env("RUST_LOG", "debug")
+            .output()
+            .unwrap_or_else(|e| panic!("Unable to start child process: {}", e));
+        if !out.status.success() {
+            println!("test failed: {}", out.status);
+            println!("--- stdout\n{}", str::from_utf8(&out.stdout).unwrap());
+            println!("--- stderr\n{}", str::from_utf8(&out.stderr).unwrap());
+            process::exit(1);
+        }
+    }
+}