[lldb-dev] PATCH for REVIEW: Implement Host::SetThreadName on Linux

[Mike Sartain]

> This is my first submission, so any feedback/comments on anything I'm messing up ...

And, of course, I did screw it up. I just ran across ThreadCreated and noticed that's where thread names are being set for OSX.

Updated patch:
- Host::SetThreadName was declared void, but the comments in Host.h said it returns a bool. It now returns true on success, false on failure.
- Host::SetThreadName is now implemented on Linux.
- Added code to set the lldb thread name in Host::ThreadCreated() in linux/Host.cpp

Path down below, and also: https://gist.github.com/mikesartain/5550857

Thanks!
 -Mike

Index: source/Host/common/Host.cpp
===================================================================
--- source/Host/common/Host.cpp	(revision 181496)
+++ source/Host/common/Host.cpp	(working copy)
@@ -512,7 +512,8 @@
 {
 }
 
-#if !defined (__APPLE__) && !defined (__FreeBSD__) // see macosx/Host.mm
+#if !defined (__APPLE__) && !defined (__FreeBSD__) && !defined (__linux__) // see macosx/Host.mm
+
 void
 Host::ThreadCreated (const char *thread_name)
 {
@@ -531,7 +532,7 @@
     return 0;
 }
 
-#endif
+#endif // #if !defined (__APPLE__) && !defined (__FreeBSD__) && !defined (__linux__)
 
 struct HostThreadCreateInfo
 {
@@ -652,7 +653,7 @@
     return thread_name;
 }
 
-void
+bool
 Host::SetThreadName (lldb::pid_t pid, lldb::tid_t tid, const char *name)
 {
 #if defined(__APPLE__) && MAC_OS_X_VERSION_MAX_ALLOWED > MAC_OS_X_VERSION_10_5
@@ -667,8 +668,33 @@
     // Set the pthread name if possible
     if (pid == curr_pid && tid == curr_tid)
     {
-        ::pthread_setname_np (name);
+        if (::pthread_setname_np (name) == 0)
+            return true;
     }
+    return false;
+#elif defined (__linux__)
+    void *fn = dlsym (RTLD_DEFAULT, "pthread_setname_np");
+    if (fn)
+    {
+        int (*pthread_setname_np_func)(pthread_t thread, const char *name);
+        *reinterpret_cast<void **> (&pthread_setname_np_func) = fn;
+
+        lldb::pid_t curr_pid = Host::GetCurrentProcessID();
+        lldb::tid_t curr_tid = Host::GetCurrentThreadID();
+
+        if (pid == LLDB_INVALID_PROCESS_ID)
+            pid = curr_pid;
+
+        if (tid == LLDB_INVALID_THREAD_ID)
+            tid = curr_tid;
+
+        if (pid == curr_pid)
+        {
+            if (pthread_setname_np_func (tid, name) == 0)
+                return true;
+        }
+    }
+    return false;
 #endif
 }
 
Index: source/Host/linux/Host.cpp
===================================================================
--- source/Host/linux/Host.cpp	(revision 181496)
+++ source/Host/linux/Host.cpp	(working copy)
@@ -169,4 +169,51 @@
     // FIXME: Parse /proc/<pid>/status to get uid, gid, euid, egid and parent_pid
 
     return true;
-}
\ No newline at end of file
+}
+
+void
+Host::ThreadCreated (const char *thread_name)
+{
+    if (!Host::SetThreadName (LLDB_INVALID_PROCESS_ID, LLDB_INVALID_THREAD_ID, thread_name))
+    {
+        // pthread_setname_np_func can fail if the thread name is longer than
+        //  the supported limit on Linux. When this occurs, the error ERANGE is returned
+        // and SetThreadName will fail. Let's drop it down to 16 characters and try again.
+        char namebuf[16];
+
+        // Thread names are coming in like '<lldb.comm.debugger.edit>' and '<lldb.comm.debugger.editline>'
+        // So just chopping the end of the string off leads to a lot of similar named threads.
+        // Go through the thread name and search for the last dot and use that.
+        const char *lastdot = ::strrchr( thread_name, '.' );
+
+        if (lastdot && lastdot != thread_name)
+            thread_name = lastdot + 1;
+        ::strncpy (namebuf, thread_name, sizeof(namebuf));
+        namebuf[ sizeof(namebuf) - 1 ] = 0;
+
+        int namebuflen = strlen(namebuf);
+        if (namebuflen > 0)
+        {
+            if (namebuf[namebuflen - 1] == '(' || namebuf[namebuflen - 1] == '>')
+            {
+                // Trim off trailing '(' and '>' characters for a bit more cleanup.
+                namebuflen--;
+                namebuf[namebuflen] = 0;
+            }
+            Host::SetThreadName (LLDB_INVALID_PROCESS_ID, LLDB_INVALID_THREAD_ID, namebuf);
+        }
+    }
+}
+
+void
+Host::Backtrace (Stream &strm, uint32_t max_frames)
+{
+    // TODO: Is there a way to backtrace the current process on linux?
+}
+
+size_t
+Host::GetEnvironment (StringList &env)
+{
+    // TODO: Is there a way to the host environment for this process on linux?
+    return 0;
+}
Index: include/lldb/Host/Host.h
===================================================================
--- include/lldb/Host/Host.h	(revision 181496)
+++ include/lldb/Host/Host.h	(working copy)
@@ -299,7 +299,7 @@
     ///     \b true if the thread name was able to be set, \b false
     ///     otherwise.
     //------------------------------------------------------------------
-    static void
+    static bool
     SetThreadName (lldb::pid_t pid, lldb::tid_t tid, const char *name);
 
     //------------------------------------------------------------------