Changes for Bug 25251

[ravitheja]

Summary

The solution to bug 24074,rL249673 needed
to parse the function information from the Dwarf in order
to set the SymbolContext. For that, GetFunction was called
for the parent in GetTypeForDIE, which parses the
ChildParameters and in the flow, GetTypeForDIE was called
for one of the sibling die and so an infinite
loop was triggered by calling GetFunction repeatedly for the
same function.

The changes in this revision modify the GetTypeForDIE to only
resolve the function context in the Type Lookup flow and so
prevent the infinite loop.

A testcase has also been added to check for regression in the
future and a test vector had been added to the testcase of
24074.

[tberghammer]

Looks good, but it would be nice if you can create a smaller test case based on your understanding of the bug

[ravitheja]

Hi Tamas,

I did spend sometime to reproduce the error with a simpler testcase but i was unsuccessful.

[ravitheja]

Changes for new testsuite format.

packages/Python/lldbsuite/test/functionalities/thread/backtrace_all/Makefile

+LEVEL = ../../../make
+
+CXXFLAGS += -std=c++11
+CXX_SOURCES := ParallelTask.cpp
+ENABLE_STD_THREADS := YES
+include $(LEVEL)/Makefile.rules

packages/Python/lldbsuite/test/functionalities/thread/backtrace_all/ParallelTask.cpp

+#include <cstdint>
+#include <thread>
+#include <vector>
+#include <queue>
+#include <future>
+#include <iostream>
+#include <cassert>
+
+class TaskPoolImpl
+{
+public:
+    TaskPoolImpl(uint32_t num_threads) :
+        m_stop(false)
+    {
+        for (uint32_t i = 0; i < num_threads; ++i)
+            m_threads.emplace_back(Worker, this);
+    }
+
+    ~TaskPoolImpl()
+    {
+        Stop();
+    }
+
+    template<typename F, typename... Args>
+    std::future<typename std::result_of<F(Args...)>::type>
+    AddTask(F&& f, Args&&... args)
+    {
+        auto task = std::make_shared<std::packaged_task<typename std::result_of<F(Args...)>::type()>>(
+            std::bind(std::forward<F>(f), std::forward<Args>(args)...));
+
+        std::unique_lock<std::mutex> lock(m_tasks_mutex);
+        assert(!m_stop && "Can't add task to TaskPool after it is stopped");
+        m_tasks.emplace([task](){ (*task)(); });
+        lock.unlock();
+        m_tasks_cv.notify_one();
+
+        return task->get_future();
+    }
+
+    void
+    Stop()
+    {
+        std::unique_lock<std::mutex> lock(m_tasks_mutex);
+        m_stop = true;
+        m_tasks_mutex.unlock();
+        m_tasks_cv.notify_all();
+        for (auto& t : m_threads)
+            t.join();
+    }
+
+private:
+    static void
+    Worker(TaskPoolImpl* pool)
+    {
+        while (true)
+        {
+            std::unique_lock<std::mutex> lock(pool->m_tasks_mutex);
+            if (pool->m_tasks.empty())
+                pool->m_tasks_cv.wait(lock, [pool](){ return !pool->m_tasks.empty() || pool->m_stop; });
+            if (pool->m_tasks.empty())
+                break;
+
+            std::function<void()> f = pool->m_tasks.front();
+            pool->m_tasks.pop();
+            lock.unlock();
+
+            f();
+        }
+    }
+
+    std::queue<std::function<void()>> m_tasks;
+    std::mutex                        m_tasks_mutex;
+    std::condition_variable           m_tasks_cv;
+    bool                              m_stop;
+    std::vector<std::thread>          m_threads;
+};
+
+class TaskPool
+{
+public:
+    // Add a new task to the thread pool and return a std::future belongs for the newly created task.
+    // The caller of this function have to wait on the future for this task to complete.
+    template<typename F, typename... Args>
+    static std::future<typename std::result_of<F(Args...)>::type>
+    AddTask(F&& f, Args&&... args)
+    {
+        return GetImplementation().AddTask(std::forward<F>(f), std::forward<Args>(args)...);
+    }
+
+    // Run all of the specified tasks on the thread pool and wait until all of them are finished
+    // before returning
+    template<typename... T>
+    static void
+    RunTasks(T&&... t)
+    {
+        RunTaskImpl<T...>::Run(std::forward<T>(t)...);
+    }
+
+private:
+    static TaskPoolImpl&
+    GetImplementation()
+    {
+        static TaskPoolImpl g_task_pool_impl(std::thread::hardware_concurrency());
+        return g_task_pool_impl;
+    }
+
+    template<typename... T>
+    struct RunTaskImpl;
+};
+
+template<typename H, typename... T>
+struct TaskPool::RunTaskImpl<H, T...>
+{
+    static void
+    Run(H&& h, T&&... t)
+    {
+        auto f = AddTask(std::forward<H>(h));
+        RunTaskImpl<T...>::Run(std::forward<T>(t)...);
+        f.wait();
+    }
+};
+
+template<>
+struct TaskPool::RunTaskImpl<>
+{
+    static void
+    Run() {}
+};
+
+int main()
+{
+    std::vector<std::future<uint32_t>> tasks;
+    for (int i = 0; i < 100000; ++i)
+    {
+        tasks.emplace_back(TaskPool::AddTask([](int i){
+            uint32_t s = 0;
+            for (int j = 0; j <= i; ++j)
+                s += j;
+            return s;
+        },
+        i));
+    }
+
+    for (auto& it : tasks)  // Set breakpoint here
+        it.wait();
+
+    TaskPool::RunTasks(
+        []() { return 1; },
+        []() { return "aaaa"; }
+    );
+}

packages/Python/lldbsuite/test/functionalities/thread/backtrace_all/TestBacktraceAll.py

+"""
+Test regression for Bug 25251.
+"""
+
+import os, time
+import unittest2
+import lldb
+from lldbsuite.test.lldbtest import *
+import lldbsuite.test.lldbutil as lldbutil
+
+class BreakpointAfterJoinTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def setUp(self):
+        # Call super's setUp().
+        TestBase.setUp(self)
+        # Find the line number for our breakpoint.
+        self.breakpoint = line_number('ParallelTask.cpp', '// Set breakpoint here')
+
+    def test(self):
+        """Test breakpoint handling after a thread join."""
+        self.build(dictionary=self.getBuildFlags())
+
+        exe = os.path.join(os.getcwd(), "a.out")
+        self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
+
+        # This should create a breakpoint
+        lldbutil.run_break_set_by_file_and_line (self, "ParallelTask.cpp", self.breakpoint, num_expected_locations=-1)
+
+        # The breakpoint list should show 1 location.
+        self.expect("breakpoint list -f", "Breakpoint location shown correctly",
+            substrs = ["1: file = 'ParallelTask.cpp', line = %d, exact_match = 0" % self.breakpoint])
+
+        # Run the program.
+        self.runCmd("run", RUN_SUCCEEDED)
+
+        # The stop reason of the thread should be breakpoint.
+        self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
+            substrs = ['stopped',
+                       'stop reason = breakpoint'])
+
+        # This should not result in a segmentation fault
+        self.expect("thread backtrace all", STOPPED_DUE_TO_BREAKPOINT,
+            substrs = ["stop reason = breakpoint 1."])
+
+        # Run to completion
+        self.runCmd("continue")
+
+if __name__ == '__main__':
+    import atexit
+    lldb.SBDebugger.Initialize()
+    atexit.register(lambda: lldb.SBDebugger.Terminate())
+    unittest2.main()

packages/Python/lldbsuite/test/lang/c/typedef/Testtypedef.py

def test_with_dwarf(self):
         """Test 'image lookup -t a' and check for correct display at different scopes."""
         self.buildDwarf()
         self.image_lookup_for_multiple_typedefs()
 
     def image_lookup_for_multiple_typedefs(self):
         """Test 'image lookup -t a' at different scopes and check for correct display."""
         exe = os.path.join(os.getcwd(), "a.out")
         self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
-        typearray = ("float", "float", "char", "float", "int", "double", "float", "float")
+        typearray = ("float", "float", "char", "double *", "float", "int", "double", "float", "float")
         arraylen = len(typearray)+1
         for i in range(1,arraylen):
             loc_line = line_number('main.c', '// Set break point ' + str(i) + '.')
             lldbutil.run_break_set_by_file_and_line (self, "main.c",loc_line, num_expected_locations=1, loc_exact=True)
 
         self.runCmd("run", RUN_SUCCEEDED)
 
         for t in typearray:
             self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
             substrs = ['stopped', 'stop reason = breakpoint'])
             self.expect("image lookup -t a", DATA_TYPES_DISPLAYED_CORRECTLY,
             substrs = ['name = "' + t + '"'])
             self.runCmd("continue")

packages/Python/lldbsuite/test/lang/c/typedef/main.c

 //===-- main.c --------------------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+void test()
+{
+    typedef double * a;
+    a b = 0; // Set break point 4.
+}
 int main (int argc, char const *argv[])
 {
     typedef float a;
     int i = 0; // Set break point 1.
     i++;
     a floatvariable = 2.7; // Set break point 2.
     {
         typedef char a;
         i++;
         a charvariable = 'a'; // Set break point 3.
+        test();
     }
     {
         int c = 0;
-        c++; // Set break point 4.
+        c++; // Set break point 5.
         for(i = 0 ; i < 1 ; i++)
         {
             typedef int a;
             a b;
-            b = 7; // Set break point 5.
+            b = 7; // Set break point 6.
         }
         for(i = 0 ; i < 1 ; i++)
         {
             typedef double a;
             a b;
-            b = 3.14; // Set break point 6.
+            b = 3.14; // Set break point 7.
         }
-        c = 1; // Set break point 7.
+        c = 1; // Set break point 8.
     }
     floatvariable = 2.5;
-    floatvariable = 2.8; // Set break point 8.
+    floatvariable = 2.8; // Set break point 9.
     return 0;
 }

source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h

public:
     lldb_private::Type *
     ResolveTypeUID(lldb::user_id_t type_uid) override;
 
     bool
     CompleteType (lldb_private::CompilerType& compiler_type) override;
 
     lldb_private::Type *
     ResolveType (const DWARFDIE &die,
-                 bool assert_not_being_parsed = true);
+                 bool assert_not_being_parsed = true,
+                 bool resolve_function_context = false);
 
     lldb_private::CompilerDecl
     GetDeclForUID (lldb::user_id_t uid) override;
 
     lldb_private::CompilerDeclContext
     GetDeclContextForUID (lldb::user_id_t uid) override;
 
     lldb_private::CompilerDeclContext
protected:
     GetObjCClassSymbol (const lldb_private::ConstString &objc_class_name);
 
     void
     ParseFunctions (const DIEArray &die_offsets,
                     bool include_inlines,
                     lldb_private::SymbolContextList& sc_list);
 
     lldb::TypeSP
-    GetTypeForDIE (const DWARFDIE &die);
+    GetTypeForDIE (const DWARFDIE &die, bool resolve_function_context = false);
 
     void
     Index();
     
     void
     DumpIndexes();
 
     void

source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

SymbolFileDWARF::CompleteType (CompilerType &compiler_type)
     assert (compiler_type);
     DWARFASTParser *dwarf_ast = dwarf_die.GetDWARFParser();
     if (dwarf_ast)
         return dwarf_ast->CompleteTypeFromDWARF (dwarf_die, type, compiler_type);
     return false;
 }
 
 Type*
-SymbolFileDWARF::ResolveType (const DWARFDIE &die, bool assert_not_being_parsed)
+SymbolFileDWARF::ResolveType (const DWARFDIE &die, bool assert_not_being_parsed, bool resolve_function_context)
 {
     if (die)
     {
         Type *type = GetDIEToType().lookup (die.GetDIE());
 
         if (type == NULL)
-            type = GetTypeForDIE (die).get();
+            type = GetTypeForDIE (die, resolve_function_context).get();
 
         if (assert_not_being_parsed)
         { 
             if (type != DIE_IS_BEING_PARSED)
                 return type;
             
             GetObjectFile()->GetModule()->ReportError ("Parsing a die that is being parsed die: 0x%8.8x: %s %s",
                                                        die.GetOffset(),
if (num_die_matches)
             const DIERef& die_ref = die_offsets[i];
             DWARFDIE die = debug_info->GetDIE (die_ref);
 
             if (die)
             {
                 if (!DIEInDeclContext(parent_decl_ctx, die))
                     continue; // The containing decl contexts don't match
 
-                Type *matching_type = ResolveType (die);
+                Type *matching_type = ResolveType (die, true, true);
                 if (matching_type)
                 {
                     // We found a type pointer, now find the shared pointer form our type list
                     types.InsertUnique (matching_type->shared_from_this());
                     if (types.GetSize() >= max_matches)
                         break;
                 }
             }
if (log && namespace_decl_ctx)
                                                   static_cast<const void*>(namespace_decl_ctx.GetOpaqueDeclContext()),
                                                   namespace_decl_ctx.GetName().AsCString("<NULL>"));
     }
 
     return namespace_decl_ctx;
 }
 
 TypeSP
-SymbolFileDWARF::GetTypeForDIE (const DWARFDIE &die)
+SymbolFileDWARF::GetTypeForDIE (const DWARFDIE &die, bool resolve_function_context)
 {
     TypeSP type_sp;
     if (die)
     {
         Type *type_ptr = GetDIEToType().lookup (die.GetDIE());
         if (type_ptr == NULL)
         {
             CompileUnit* lldb_cu = GetCompUnitForDWARFCompUnit(die.GetCU());
             assert (lldb_cu);
             SymbolContext sc(lldb_cu);
             const DWARFDebugInfoEntry* parent_die = die.GetParent().GetDIE();
             while (parent_die != nullptr)
                 {
                     if (parent_die->Tag() == DW_TAG_subprogram)
                         break;
                     parent_die = parent_die->GetParent();
                 }
             SymbolContext sc_backup = sc;
-            if (parent_die != nullptr && !GetFunction(DWARFDIE(die.GetCU(),parent_die), sc))
+            if (resolve_function_context && parent_die != nullptr && !GetFunction(DWARFDIE(die.GetCU(),parent_die), sc))
                 sc = sc_backup;
 
             type_sp = ParseType(sc, die, NULL);
         }
         else if (type_ptr != DIE_IS_BEING_PARSED)
         {
             // Grab the existing type from the master types lists
             type_sp = type_ptr->shared_from_this();
if (num_matches)
                 
                 if (try_resolving_type)
                 {
                     if (must_be_implementation && type_die.Supports_DW_AT_APPLE_objc_complete_type())
                         try_resolving_type = type_die.GetAttributeValueAsUnsigned (DW_AT_APPLE_objc_complete_type, 0);
                     
                     if (try_resolving_type)
                     {
-                        Type *resolved_type = ResolveType (type_die, false);
+                        Type *resolved_type = ResolveType (type_die, false, true);
                         if (resolved_type && resolved_type != DIE_IS_BEING_PARSED)
                         {
                             DEBUG_PRINTF ("resolved 0x%8.8" PRIx64 " from %s to 0x%8.8" PRIx64 " (cu 0x%8.8" PRIx64 ")\n",
                                           die.GetID(),
                                           m_obj_file->GetFileSpec().GetFilename().AsCString("<Unknown>"),
                                           type_die.GetID(),
                                           type_cu->GetID());