From: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Date: Sat, 3 May 2026 18:00:00 +0000
Subject: Bug 2038068 - Make abseil-cpp use the Win32 path on mingw. r?#firefox-build-system-reviewers

The __MINGW32__ branches in absl's thread_identity and waiter code
assume winpthreads is available, but Mozilla's clangmingw toolchain
doesn't ship pthread headers. Drop the carve-outs so mingw uses absl's
native Windows path (CPP11 thread_local + win32_waiter), which clang
already supports for the mingw target.
---
 abseil-cpp/absl/base/internal/thread_identity.cc            | 8 ++++----
 abseil-cpp/absl/base/internal/thread_identity.h             | 2 +-
 abseil-cpp/absl/synchronization/internal/pthread_waiter.h   | 4 ++--
 abseil-cpp/absl/synchronization/internal/win32_waiter.h     | 4 ++--
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/abseil-cpp/absl/base/internal/thread_identity.cc b/abseil-cpp/absl/base/internal/thread_identity.cc
index 0471a25dceab..8b918843541c 100644
--- a/abseil-cpp/absl/base/internal/thread_identity.cc
+++ b/abseil-cpp/absl/base/internal/thread_identity.cc
@@ -14,7 +14,7 @@
 
 #include "absl/base/internal/thread_identity.h"
 
-#if !defined(_WIN32) || defined(__MINGW32__)
+#if !defined(_WIN32)
 #include <pthread.h>
 #ifndef __wasi__
 // WASI does not provide this header, either way we disable use
@@ -84,9 +84,9 @@ void SetCurrentThreadIdentity(ThreadIdentity* identity,
   absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey,
                   reclaimer);
 
-#if defined(__wasi__) || defined(__EMSCRIPTEN__) || defined(__MINGW32__) || \
+#if defined(__wasi__) || defined(__EMSCRIPTEN__) || \
     defined(__hexagon__)
-  // Emscripten, WASI and MinGW pthread implementations does not support
+  // Emscripten and WASI pthread implementations does not support
   // signals. See
   // https://kripken.github.io/emscripten-site/docs/porting/pthreads.html for
   // more information.
@@ -106,7 +106,7 @@ void SetCurrentThreadIdentity(ThreadIdentity* identity,
   pthread_setspecific(thread_identity_pthread_key,
                       reinterpret_cast<void*>(identity));
   pthread_sigmask(SIG_SETMASK, &curr_signals, nullptr);
-#endif  // !__EMSCRIPTEN__ && !__MINGW32__
+#endif  // !__EMSCRIPTEN__
 
 #elif ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS
   // NOTE: Not async-safe.  But can be open-coded.
diff --git a/abseil-cpp/absl/base/internal/thread_identity.h b/abseil-cpp/absl/base/internal/thread_identity.h
index acfc15a8f697..6a538897660c 100644
--- a/abseil-cpp/absl/base/internal/thread_identity.h
+++ b/abseil-cpp/absl/base/internal/thread_identity.h
@@ -217,7 +217,7 @@ void ClearCurrentThreadIdentity();
 #error ABSL_THREAD_IDENTITY_MODE cannot be directly set
 #elif defined(ABSL_FORCE_THREAD_IDENTITY_MODE)
 #define ABSL_THREAD_IDENTITY_MODE ABSL_FORCE_THREAD_IDENTITY_MODE
-#elif defined(_WIN32) && !defined(__MINGW32__)
+#elif defined(_WIN32)
 #define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11
 #elif defined(__APPLE__) && defined(ABSL_HAVE_THREAD_LOCAL)
 #define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11
diff --git a/abseil-cpp/absl/synchronization/internal/pthread_waiter.h b/abseil-cpp/absl/synchronization/internal/pthread_waiter.h
index 23db76ad442e..eb30b24d0e3b 100644
--- a/abseil-cpp/absl/synchronization/internal/pthread_waiter.h
+++ b/abseil-cpp/absl/synchronization/internal/pthread_waiter.h
@@ -16,7 +16,7 @@
 #ifndef ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
 #define ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
 
-#if !defined(_WIN32) && !defined(__MINGW32__)
+#if !defined(_WIN32)
 #include <pthread.h>
 
 #include "absl/base/config.h"
@@ -55,6 +55,6 @@ class PthreadWaiter : public WaiterCrtp<PthreadWaiter> {
 ABSL_NAMESPACE_END
 }  // namespace absl
 
-#endif  // !defined(_WIN32) && !defined(__MINGW32__)
+#endif  // !defined(_WIN32)
 
 #endif  // ABSL_SYNCHRONIZATION_INTERNAL_PTHREAD_WAITER_H_
diff --git a/abseil-cpp/absl/synchronization/internal/win32_waiter.h b/abseil-cpp/absl/synchronization/internal/win32_waiter.h
index fdab264e8cb7..cba1c9d8834f 100644
--- a/abseil-cpp/absl/synchronization/internal/win32_waiter.h
+++ b/abseil-cpp/absl/synchronization/internal/win32_waiter.h
@@ -20,7 +20,7 @@
 #include <sdkddkver.h>
 #endif
 
-#if defined(_WIN32) && !defined(__MINGW32__) && \
+#if defined(_WIN32) && \
     _WIN32_WINNT >= _WIN32_WINNT_VISTA
 
 #include "absl/base/config.h"
@@ -66,7 +66,7 @@ class Win32Waiter : public WaiterCrtp<Win32Waiter> {
 ABSL_NAMESPACE_END
 }  // namespace absl
 
-#endif  // defined(_WIN32) && !defined(__MINGW32__) &&
+#endif  // defined(_WIN32) &&
         // _WIN32_WINNT >= _WIN32_WINNT_VISTA
 
 #endif  // ABSL_SYNCHRONIZATION_INTERNAL_WIN32_WAITER_H_