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[lldb] add support for thread names on Windows #74731

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merged 3 commits into from
Dec 21, 2023
Merged

[lldb] add support for thread names on Windows #74731

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9383b8b
lldb: add support for thread names on Windows
oltolm Dec 1, 2023
89ea63c
[lldb] add unit test for Windows thread names
oltolm Dec 8, 2023
da9125b
lldb: cleanup Windows thread names
oltolm Dec 12, 2023
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31 changes: 31 additions & 0 deletions lldb/source/Plugins/Process/Windows/Common/TargetThreadWindows.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
#include "lldb/Utility/LLDBLog.h"
#include "lldb/Utility/Log.h"
#include "lldb/Utility/State.h"
#include "llvm/Support/ConvertUTF.h"

#include "ProcessWindows.h"
#include "ProcessWindowsLog.h"
Expand All @@ -33,6 +34,9 @@
using namespace lldb;
using namespace lldb_private;

using GetThreadDescriptionFunctionPtr = HRESULT
WINAPI (*)(HANDLE hThread, PWSTR *ppszThreadDescription);

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TargetThreadWindows::TargetThreadWindows(ProcessWindows &process,
const HostThread &thread)
: Thread(process, thread.GetNativeThread().GetThreadId()),
Expand Down Expand Up @@ -175,3 +179,30 @@ Status TargetThreadWindows::DoResume() {

return Status();
}

const char *TargetThreadWindows::GetName() {
Log *log = GetLog(LLDBLog::Thread);
HMODULE hModule = ::LoadLibraryW(L"Kernel32.dll");
if (hModule) {
auto GetThreadDescription =
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This should be pulled out into a lambda and store the lookup rather than re-evaluating it each time.

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done

reinterpret_cast<GetThreadDescriptionFunctionPtr>(
::GetProcAddress(hModule, "GetThreadDescription"));
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This code is only compiled on windows, why do we need to get the library handle manually and get the function pointer. Can't we just #include <processthreadsapi.h> and then call the function directly?

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@Fulgen301 Fulgen301 Dec 7, 2023 •
edited
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The function was added in Windows 10 1607, which was also the only build (excluding Server 2016) where it isn't available in the header:

Windows Server 2016, Windows 10 LTSB 2016 and Windows 10 version 1607: GetThreadDescription is only available by Run Time Dynamic Linking in KernelBase.dll.

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If there is compatibility that we are concerned about, I think that we should consider falling back to more ... esoteric solutions.

__try {
  RaiseException(MS_VC_EXCEPTION, 0, sizeof(info) / sizeof(ULONG_PTR), (ULONG_PTR*)&info);  
} __except (EXCEPTION_EXECUTE_HANDLER) {
}

Should be far more portable and is what VS also uses. This is documented at https://learn.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2015/debugger/how-to-set-a-thread-name-in-native-code?view=vs-2015&redirectedfrom=MSDN.

I would be okay with also raising the requirements to a newer version of Windows as 1607 is RS1 which makes it more than 8 years old at this point.

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You are talking about setting thread names, but I implemented getting a thread name from Windows.

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There is the set name below though.

LLDB_LOGF(log, "GetProcAddress: %p",
reinterpret_cast<void *>(GetThreadDescription));
if (GetThreadDescription) {
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An early out here would be nice to reduce indentation.

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done

PWSTR pszThreadName;
if (SUCCEEDED(GetThreadDescription(
m_host_thread.GetNativeThread().GetSystemHandle(),
&pszThreadName))) {
LLDB_LOGF(log, "GetThreadDescription: %ls", pszThreadName);
llvm::convertUTF16ToUTF8String(
llvm::ArrayRef(reinterpret_cast<char *>(pszThreadName),
wcslen(pszThreadName) * sizeof(wchar_t)),
m_name);
::LocalFree(pszThreadName);
}
}
}

return m_name.c_str();
}
2 changes: 2 additions & 0 deletions lldb/source/Plugins/Process/Windows/Common/TargetThreadWindows.h
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ class TargetThreadWindows : public lldb_private::Thread {
lldb::RegisterContextSP
CreateRegisterContextForFrame(StackFrame *frame) override;
bool CalculateStopInfo() override;
const char *GetName() override;

Status DoResume();

Expand All @@ -42,6 +43,7 @@ class TargetThreadWindows : public lldb_private::Thread {
private:
lldb::RegisterContextSP m_thread_reg_ctx_sp;
HostThread m_host_thread;
std::string m_name;
};
} // namespace lldb_private

Expand Down