SignalDelegator: Simplify support for musl's sigset_t

Source/Tools/LinuxEmulation/CMakeLists.txt

@@ -164,29 +164,3 @@ add_custom_target(struct_verifier
   WORKING_DIRECTORY "${CMAKE_BINARY_DIR}"
   USES_TERMINAL
   COMMAND "ctest" "--output-on-failure" "--timeout" "302" ${TEST_JOB_FLAG} "-R" "Test_verify*")
-
-include(CheckCSourceCompiles)
-
-check_c_source_compiles("
-#include <signal.h>
-int main(void){
-    sigset_t s;
-    (void)sizeof(s.__val);   // glibc
-    return 0;
-}" SIGSET_HAS___VAL)
-
-check_c_source_compiles("
-#include <signal.h>
-int main(void){
-    sigset_t s;
-    (void)sizeof(s.__bits);  // musl
-    return 0;
-}" SIGSET_HAS___BITS)
-
-if(SIGSET_HAS___VAL)
-  add_compile_definitions("SIGSET_VAL=__val")
-elseif(SIGSET_HAS___BITS)
-  add_compile_definitions("SIGSET_VAL=__bits")
-else()
-  message(FATAL_ERROR "Unknown sigset_t layout!")
-endif()

Source/Tools/LinuxEmulation/LinuxSyscalls/SignalDelegator.cpp

@@ -649,17 +649,19 @@ void SignalDelegator::HandleGuestSignal(FEX::HLE::ThreadStateObject* ThreadObjec
                        "capacity size. This will "
                        "likely crash! Asserting now!");
 
+    // Peek into sigset_t implementation details, extracting the __val member for glibc and __bits for musl
+    auto& [sigmask_val] = _context->uc_sigmask;
+    static_assert(sizeof(sigmask_val[0]) == sizeof(uint64_t), "Unknown sigset_t layout");
+
     ThreadObject->SignalInfo.DeferredSignalFrames.emplace_back(ThreadStateObject::DeferredSignalState {
       .Info = SigInfo,
       .Signal = Signal,
-      .SigMask = _context->uc_sigmask.SIGSET_VAL[0],
+      .SigMask = sigmask_val[0],
     });
 
-    uint64_t NewMask = GetNewSigMask(Signal);
-
     // Update our host signal mask so we don't hit race conditions with signals
     // This allows us to maintain the expected signal mask through the guest signal handling and then all the way back again
-    memcpy(&_context->uc_sigmask, &NewMask, sizeof(uint64_t));
+    sigmask_val[0] = GetNewSigMask(Signal);
 
     // Now update the faulting page permissions so it will fault on write.
     mprotect(reinterpret_cast<void*>(&Thread->InterruptFaultPage), sizeof(Thread->InterruptFaultPage), PROT_NONE);