[llvm-branch-commits] [llvm-branch] r227646 - Revert r227332, which merged in r227300: "[LPM] Rip all of ManagedStatic

[Hans Wennborg]

Author: hans
Date: Fri Jan 30 17:58:51 2015
New Revision: 227646

URL: http://llvm.org/viewvc/llvm-project?rev=227646&view=rev
Log:
Revert r227332, which merged in r227300: "[LPM] Rip all of ManagedStatic
and ThreadLocal out of the pretty stack tracing code."

The patch has been having trouble on trunk and doesn't seem ready for 3.6.
Reverting to get it out of the branch before tagging rc2.

Modified:
    llvm/branches/release_36/   (props changed)
    llvm/branches/release_36/lib/Support/PrettyStackTrace.cpp

Propchange: llvm/branches/release_36/
------------------------------------------------------------------------------
--- svn:mergeinfo (original)
+++ svn:mergeinfo Fri Jan 30 17:58:51 2015
@@ -1,3 +1,3 @@
 /llvm/branches/Apple/Pertwee:110850,110961
 /llvm/branches/type-system-rewrite:133420-134817
-/llvm/trunk:155241,226023,226029,226044,226046,226048,226058,226075,226170-226171,226182,226473,226664,226708,226711,226755,227005,227085,227250,227260-227261,227290,227294,227299-227300,227319,227339,227491,227584
+/llvm/trunk:155241,226023,226029,226044,226046,226048,226058,226075,226170-226171,226182,226473,226664,226708,226711,226755,227005,227085,227250,227260-227261,227290,227294,227299,227319,227339,227491,227584

Modified: llvm/branches/release_36/lib/Support/PrettyStackTrace.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/release_36/lib/Support/PrettyStackTrace.cpp?rev=227646&r1=227645&r2=227646&view=diff
==============================================================================
--- llvm/branches/release_36/lib/Support/PrettyStackTrace.cpp (original)
+++ llvm/branches/release_36/lib/Support/PrettyStackTrace.cpp Fri Jan 30 17:58:51 2015
@@ -16,7 +16,9 @@
 #include "llvm-c/Core.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Config/config.h"     // Get autoconf configuration settings
+#include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Signals.h"
+#include "llvm/Support/ThreadLocal.h"
 #include "llvm/Support/Watchdog.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -26,18 +28,7 @@
 
 using namespace llvm;
 
-// We need a thread local pointer to manage the stack of our stack trace
-// objects, but we *really* cannot tolerate destructors running and do not want
-// to pay any overhead of synchronizing. As a consequence, we use a raw
-// thread-local variable. Some day, we should be able to use a limited subset
-// of C++11's thread_local, but compilers aren't up for it today.
-// FIXME: This should be moved to a Compiler.h abstraction.
-#ifdef _MSC_VER // MSVC supports this with a __declspec.
-static __declspec(thread) const PrettyStackTraceEntry
-    *PrettyStackTraceHead = nullptr;
-#else // Clang, GCC, and all compatible compilers tend to use __thread.
-static __thread const PrettyStackTraceEntry *PrettyStackTraceHead = nullptr;
-#endif
+static ManagedStatic<sys::ThreadLocal<const PrettyStackTraceEntry> > PrettyStackTraceHead;
 
 static unsigned PrintStack(const PrettyStackTraceEntry *Entry, raw_ostream &OS){
   unsigned NextID = 0;
@@ -55,12 +46,12 @@ static unsigned PrintStack(const PrettyS
 /// PrintCurStackTrace - Print the current stack trace to the specified stream.
 static void PrintCurStackTrace(raw_ostream &OS) {
   // Don't print an empty trace.
-  if (!PrettyStackTraceHead) return;
+  if (!PrettyStackTraceHead->get()) return;
   
   // If there are pretty stack frames registered, walk and emit them.
   OS << "Stack dump:\n";
   
-  PrintStack(PrettyStackTraceHead, OS);
+  PrintStack(PrettyStackTraceHead->get(), OS);
   OS.flush();
 }
 
@@ -110,14 +101,26 @@ static void CrashHandler(void *) {
 
 PrettyStackTraceEntry::PrettyStackTraceEntry() {
   // Link ourselves.
-  NextEntry = PrettyStackTraceHead;
-  PrettyStackTraceHead = this;
+  NextEntry = PrettyStackTraceHead->get();
+  PrettyStackTraceHead->set(this);
 }
 
 PrettyStackTraceEntry::~PrettyStackTraceEntry() {
-  assert(PrettyStackTraceHead == this &&
+  // Do nothing if PrettyStackTraceHead is uninitialized. This can only happen
+  // if a shutdown occurred after we created the PrettyStackTraceEntry. That
+  // does occur in the following idiom:
+  //
+  // PrettyStackTraceProgram X(...);
+  // llvm_shutdown_obj Y;
+  //
+  // Without this check, we may end up removing ourselves from the stack trace
+  // after PrettyStackTraceHead has already been destroyed.
+  if (!PrettyStackTraceHead.isConstructed())
+    return;
+  
+  assert(PrettyStackTraceHead->get() == this &&
          "Pretty stack trace entry destruction is out of order");
-  PrettyStackTraceHead = getNextEntry();
+  PrettyStackTraceHead->set(getNextEntry());
 }
 
 void PrettyStackTraceString::print(raw_ostream &OS) const {