DRTVWR-494: Use std::thread::id for LLThread::currentID().

LLThread::currentID() used to return a U32, a distinct unsigned value
incremented by explicitly constructing LLThread or by calling LLThread::
registerThreadID() early in a thread launched by other means. The latter
imposed an unobvious requirement on new code based on std::thread. Using
std::thread::id instead delegates to the compiler/library the problem of
distinguishing threads launched by any means.

Change lots of explicit U32 declarations. Introduce LLThread::id_t typedef to
avoid having to run around fixing uses again if we later revisit this decision.

LLMutex, which stores an LLThread::id_t, wants a distinguished value meaning
NO_THREAD, and had an enum with that name. But as std::thread::id promises
that the default-constructed value is distinct from every valid value,
NO_THREAD becomes unnecessary and goes away.

Because LLMutex now stores LLThread::id_t instead of U32, make llmutex.h
#include "llthread.h" instead of the other way around. This makes LLMutex an
incomplete type within llthread.h, so move LLThread::lockData() and
unlockData() to the .cpp file. Similarly, remove llrefcount.h's #include
"llmutex.h" to break circularity; instead forward-declare LLMutex.

It turns out that a number of source files assumed that #include "llthread.h"
would get the definition for LLMutex. Sprinkle #include "llmutex.h" as needed.

In the SAFE_SSL code in llcorehttp/httpcommon.cpp, there's an ssl_thread_id()
callback that returns an unsigned long to the SSL library. When LLThread::
currentID() was U32, we could simply return that. But std::thread::id is very
deliberately opaque, and can't be reinterpret_cast to unsigned long.
Fortunately it can be hashed because std::hash is specialized with that type.

1 files changed, 3 insertions, 1 deletions

diff --git a/indra/llcorehttp/httpcommon.cpp b/indra/llcorehttp/httpcommon.cpp
index 7c93c54cdf..e37a38b05f 100644
--- a/indra/llcorehttp/httpcommon.cpp
+++ b/indra/llcorehttp/httpcommon.cpp
@@ -40,6 +40,7 @@
 #include <sstream>
 #if SAFE_SSL
 #include <openssl/crypto.h>
+#include <functional>               // std::hash
 #endif
 
 
@@ -369,7 +370,8 @@ void ssl_locking_callback(int mode, int type, const char *file, int line)
 //static
 unsigned long ssl_thread_id(void)
 {
-    return LLThread::currentID();
+    // std::thread::id is very deliberately opaque, but we can hash it
+    return std::hash<LLThread::id_t>()(LLThread::currentID());
 }
 #endif