Log the current task name in the log! macros.

This requires doing an allocation on log! invocations
if the current task is named, since there is no non-allocating
way to access the name of the current task.

Fixes rust-lang#2672

Author: reem

src/liblog/lib.rs

@@ -247,9 +247,10 @@ impl fmt::Show for LogLevel {
 impl Logger for DefaultLogger {
     fn log(&mut self, record: &LogRecord) {
         match writeln!(&mut self.handle,
-                       "{}:{}: {}",
+                       "{}:{}:{}: {}",
                        record.level,
                        record.module_path,
+                       record.task_name,
                        record.args) {
             Err(e) => panic!("failed to log: {}", e),
             Ok(()) => {}
@@ -275,7 +276,7 @@ impl Drop for DefaultLogger {
 /// It is not recommended to call this function directly, rather it should be
 /// invoked through the logging family of macros.
 #[doc(hidden)]
-pub fn log(level: u32, loc: &'static LogLocation, args: &fmt::Arguments) {
+pub fn log(level: u32, loc: LogLocation, args: &fmt::Arguments) {
     // Test the literal string from args against the current filter, if there
     // is one.
     match unsafe { FILTER.as_ref() } {
@@ -297,6 +298,9 @@ pub fn log(level: u32, loc: &'static LogLocation, args: &fmt::Arguments) {
         file: loc.file,
         module_path: loc.module_path,
         line: loc.line,
+        task_name: loc.task_name
+                       .as_ref().map(|s| &**s)
+                       .unwrap_or("<unnamed>"),
     });
     set_logger(logger);
 }
@@ -335,13 +339,17 @@ pub struct LogRecord<'a> {
 
     /// The line number of where the LogRecord originated.
     pub line: uint,
+
+    /// The task name of the task where the LogRecord originated.
+    pub task_name: &'a str
 }
 
 #[doc(hidden)]
 pub struct LogLocation {
     pub module_path: &'static str,
     pub file: &'static str,
     pub line: uint,
+    pub task_name: Option<String>
 }
 
 /// Tests whether a given module's name is enabled for a particular level of

src/liblog/macros.rs

@@ -53,14 +53,15 @@
 #[macro_export]
 macro_rules! log(
     ($lvl:expr, $($arg:tt)+) => ({
-        static LOC: ::log::LogLocation = ::log::LogLocation {
-            line: line!(),
-            file: file!(),
-            module_path: module_path!(),
-        };
         let lvl = $lvl;
         if log_enabled!(lvl) {
-            format_args!(|args| { ::log::log(lvl, &LOC, args) }, $($arg)+)
+            format_args!(|args| { ::log::log(lvl, ::log::LogLocation {
+                    line: line!(),
+                    file: file!(),
+                    module_path: module_path!(),
+                    task_name: ::std::task::name()
+                }, args)
+            }, $($arg)+)
         }
     })
 )