Undo code changes and add fix in cmake

Author: Hugh Delaney

scripts/templates/libapi.cpp.mako

@@ -82,13 +82,4 @@ try {
 
 %endfor
 %endfor
-
-namespace {
-// This uselessFunc is needed to ensure that pthread is linked correctly against
-// ur_loader.so for gcc-9
-void uselessFunc() {
-    std::thread UselessThread([]{});
-}
-}
-
 } // extern "C"

source/loader/CMakeLists.txt

@@ -48,6 +48,13 @@ if (UNIX)
     set(THREADS_PREFER_PTHREAD_FLAG TRUE)
     find_package(Threads REQUIRED)
     target_link_libraries(ur_loader PRIVATE Threads::Threads)
+    # Older gcc versions need -pthread, not just -lpthread
+    if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+        if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 11.1)
+            find_library(PTHREAD_LIBRARY pthread)
+            target_link_libraries(ur_loader PRIVATE "-pthread")
+        endif()
+    endif()
 endif()
 
 if(WIN32)

source/loader/ur_lib.hpp

@@ -26,7 +26,6 @@
 #include <atomic>
 #include <mutex>
 #include <set>
-#include <thread>
 #include <vector>
 
 struct ur_loader_config_handle_t_ {

source/loader/ur_libapi.cpp

@@ -7743,12 +7743,4 @@ ur_result_t UR_APICALL urUsmP2PPeerAccessGetInfoExp(
     return exceptionToResult(std::current_exception());
 }
 
-namespace {
-// This uselessFunc is needed to ensure that pthread is linked correctly against
-// ur_loader.so for gcc-9
-void uselessFunc() {
-    std::thread UselessThread([] {});
-}
-} // namespace
-
 } // extern "C"