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@lmielick lmielick commented Sep 4, 2025

Contrary to pthread_join on Windows WaitForSingleObject does not destroy the thread handle. Add missing CloseHandle call to avoid a handle leak.

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llvmbot commented Sep 4, 2025

@llvm/pr-subscribers-platform-windows

Author: Lukasz Mielicki (lmielick)

Changes

Contrary to pthread_join on Windows WaitForSingleObject does not destroy the thread handle. Add missing CloseHandle call to avoid a handle leak.


Full diff: https://github.com/llvm/llvm-project/pull/156854.diff

1 Files Affected:

  • (modified) llvm/lib/Support/Windows/Threading.inc (+3)
diff --git a/llvm/lib/Support/Windows/Threading.inc b/llvm/lib/Support/Windows/Threading.inc
index b11f216adeba4..fd872a2b133e9 100644
--- a/llvm/lib/Support/Windows/Threading.inc
+++ b/llvm/lib/Support/Windows/Threading.inc
@@ -42,6 +42,9 @@ void llvm_thread_join_impl(HANDLE hThread) {
   if (::WaitForSingleObject(hThread, INFINITE) == WAIT_FAILED) {
     ReportLastErrorFatal("WaitForSingleObject failed");
   }
+  if (::CloseHandle(hThread) == FALSE) {
+    ReportLastErrorFatal("CloseHandle failed");
+  }
 }
 
 void llvm_thread_detach_impl(HANDLE hThread) {

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llvmbot commented Sep 4, 2025

@llvm/pr-subscribers-llvm-support

Author: Lukasz Mielicki (lmielick)

Changes

Contrary to pthread_join on Windows WaitForSingleObject does not destroy the thread handle. Add missing CloseHandle call to avoid a handle leak.


Full diff: https://github.com/llvm/llvm-project/pull/156854.diff

1 Files Affected:

  • (modified) llvm/lib/Support/Windows/Threading.inc (+3)
diff --git a/llvm/lib/Support/Windows/Threading.inc b/llvm/lib/Support/Windows/Threading.inc
index b11f216adeba4..fd872a2b133e9 100644
--- a/llvm/lib/Support/Windows/Threading.inc
+++ b/llvm/lib/Support/Windows/Threading.inc
@@ -42,6 +42,9 @@ void llvm_thread_join_impl(HANDLE hThread) {
   if (::WaitForSingleObject(hThread, INFINITE) == WAIT_FAILED) {
     ReportLastErrorFatal("WaitForSingleObject failed");
   }
+  if (::CloseHandle(hThread) == FALSE) {
+    ReportLastErrorFatal("CloseHandle failed");
+  }
 }
 
 void llvm_thread_detach_impl(HANDLE hThread) {

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lmielick commented Sep 4, 2025

@aganea @mstorsjo please have a look

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@dpaoliello dpaoliello left a comment

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LGTM - thread::join clears the handle after calling this, so we are definitely leaking at the moment:

void thread::join() {
llvm_thread_join_impl(Thread);
Thread = native_handle_type();
}

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@aganea aganea left a comment

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LGTM, just a nit.

@@ -42,6 +42,9 @@ void llvm_thread_join_impl(HANDLE hThread) {
if (::WaitForSingleObject(hThread, INFINITE) == WAIT_FAILED) {
ReportLastErrorFatal("WaitForSingleObject failed");
}
if (::CloseHandle(hThread) == FALSE) {
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@aganea aganea Sep 4, 2025

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nit: The brackets don't follow this LLVM coding standard guideline (but I know, it looks like the whole file is like that, and that should be corrected). I think we should stick to the guidelines to keep the codebase uniform.

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4 participants