[Concurrency] Use EnvVars utilities for SWIFT_IS_CURRENT_EXECUTOR_LEGACY_MODE_OVERRIDE

Author: ktoso

include/swift/Runtime/EnvironmentVariables.h

@@ -53,6 +53,10 @@ SWIFT_RUNTIME_STDLIB_SPI bool concurrencyEnableJobDispatchIntegration();
 // Concurrency library can call.
 SWIFT_RUNTIME_STDLIB_SPI bool concurrencyValidateUncheckedContinuations();
 
+// Wrapper around SWIFT_IS_CURRENT_EXECUTOR_LEGACY_MODE_OVERRIDE that the
+// Concurrency library can call.
+SWIFT_RUNTIME_STDLIB_SPI const char *concurrencyIsCurrentExecutorLegacyModeOverride();
+
 } // end namespace environment
 } // end namespace runtime
 } // end namespace swift

stdlib/public/Concurrency/Actor.cpp

@@ -30,6 +30,7 @@
 #include "swift/Runtime/Bincompat.h"
 #include "swift/Runtime/Casting.h"
 #include "swift/Runtime/DispatchShims.h"
+#include "swift/Runtime/EnvironmentVariables.h"
 #include "swift/Threading/Mutex.h"
 #include "swift/Threading/Once.h"
 #include "swift/Threading/Thread.h"
@@ -352,8 +353,8 @@ static void checkIsCurrentExecutorMode(void *context) {
   // Potentially, override the platform detected mode, primarily used in tests.
 #if SWIFT_STDLIB_HAS_ENVIRON
   if (const char *modeStr =
-          getenv("SWIFT_IS_CURRENT_EXECUTOR_LEGACY_MODE_OVERRIDE")) {
-    if (modeStr && *modeStr) {
+          runtime::environment::concurrencyIsCurrentExecutorLegacyModeOverride()) {
+    if (modeStr) {
       if (strcmp(modeStr, "nocrash") == 0) {
         useLegacyMode = true;
       } else if (strcmp(modeStr, "crash") == 0) {

stdlib/public/runtime/EnvironmentVariables.cpp

@@ -272,3 +272,7 @@ SWIFT_RUNTIME_STDLIB_SPI bool concurrencyEnableJobDispatchIntegration() {
 SWIFT_RUNTIME_STDLIB_SPI bool concurrencyValidateUncheckedContinuations() {
   return runtime::environment::SWIFT_DEBUG_VALIDATE_UNCHECKED_CONTINUATIONS();
 }
+
+SWIFT_RUNTIME_STDLIB_SPI const char *concurrencyIsCurrentExecutorLegacyModeOverride() {
+  return runtime::environment::SWIFT_IS_CURRENT_EXECUTOR_LEGACY_MODE_OVERRIDE();
+}

stdlib/public/runtime/EnvironmentVariables.def

@@ -119,4 +119,17 @@ VARIABLE(SWIFT_BACKTRACE, string, "",
          "crash catching and backtracing support in the runtime. "
          "See docs/Backtracing.rst in the Swift repository for details.")
 
+VARIABLE(SWIFT_IS_CURRENT_EXECUTOR_LEGACY_MODE_OVERRIDE, string, "",
+         "Allows for suppressing 'is current executor' equality check crashes. "
+         "As since Swift 6.0 checking for current executor equality, may crash "
+         "and will never return 'false' because we are calling into library "
+         "implemented SerialExecutor.checkIsolation which should crash if the "
+         "isolation is not the expected one. Some old code may rely on the "
+         "non-crashing behavior. This flag enables temporarily restoring the "
+         "legacy 'nocrash' behavior until adopting code has been adjusted.\n"
+         "\n"
+         "Legal values are: \n"
+         "  - nocrash (Legacy behavior)\n"
+         "  - crash (Swift 6.0+ behavior)")
+
 #undef VARIABLE