[stdlib] Add build option to enable _debugPrecondition in Release mode

CMakeLists.txt

@@ -434,6 +434,10 @@ option(SWIFT_ENABLE_STDLIBCORE_EXCLUSIVITY_CHECKING
   "Build stdlibCore with exclusivity checking enabled"
   FALSE)
 
+option(SWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE
+  "Enable _debugPrecondition checks in the stdlib in Release configurations"
+  FALSE)
+
 option(SWIFT_ENABLE_EXPERIMENTAL_DIFFERENTIABLE_PROGRAMMING
   "Enable experimental Swift differentiable programming features"
   FALSE)

stdlib/public/core/Assert.swift

@@ -261,24 +261,32 @@ internal func _debugPrecondition(
   _ condition: @autoclosure () -> Bool, _ message: StaticString = StaticString(),
   file: StaticString = #file, line: UInt = #line
 ) {
+#if SWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE
+  _precondition(condition(), message, file: file, line: line)
+#else
   // Only check in debug mode.
   if _slowPath(_isDebugAssertConfiguration()) {
     if !_fastPath(condition()) {
       _fatalErrorMessage("Fatal error", message, file: file, line: line,
         flags: _fatalErrorFlags())
     }
   }
+#endif
 }
 
 @usableFromInline @_transparent
 internal func _debugPreconditionFailure(
   _ message: StaticString = StaticString(),
   file: StaticString = #file, line: UInt = #line
 ) -> Never {
+#if SWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE
+  _preconditionFailure(message, file: file, line: line)
+#else
   if _slowPath(_isDebugAssertConfiguration()) {
     _precondition(false, message, file: file, line: line)
   }
   _conditionallyUnreachable()
+#endif
 }
 
 /// Internal checks.

stdlib/public/core/AssertCommon.swift

@@ -58,6 +58,17 @@ func _isStdlibInternalChecksEnabled() -> Bool {
 #endif
 }
 
+@_transparent
+@_alwaysEmitIntoClient // Introduced in 5.7
+public // @testable
+func _isStdlibDebugChecksEnabled() -> Bool {
+#if SWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE
+  return !_isFastAssertConfiguration()
+#else
+  return _isDebugAssertConfiguration()
+#endif
+}
+
 @usableFromInline @_transparent
 internal func _fatalErrorFlags() -> UInt32 {
   // The current flags are:

stdlib/public/core/CMakeLists.txt

@@ -272,6 +272,9 @@ endif()
 if(SWIFT_STDLIB_ENABLE_STDLIBCORE_EXCLUSIVITY_CHECKING)
   list(APPEND swift_stdlib_compile_flags "-enforce-exclusivity=checked")
 endif()
+if(SWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE)
+  list(APPEND swift_stdlib_compile_flags "-DSWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE")
+endif()
 set(compile_flags_for_final_build)
 if(SWIFT_ENABLE_ARRAY_COW_CHECKS)
   list(APPEND compile_flags_for_final_build "-DCOW_CHECKS_ENABLED")

test/CMakeLists.txt

@@ -202,6 +202,7 @@ normalize_boolean_spelling(SWIFT_OPTIMIZED)
 normalize_boolean_spelling(SWIFT_STDLIB_SINGLE_THREADED_RUNTIME)
 normalize_boolean_spelling(SWIFT_ENABLE_REFLECTION)
 normalize_boolean_spelling(SWIFT_ENABLE_RUNTIME_FUNCTION_COUNTERS)
+normalize_boolean_spelling(SWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE)
 normalize_boolean_spelling(SWIFT_HAVE_LIBXML2)
 normalize_boolean_spelling(SWIFT_INCLUDE_TOOLS)
 normalize_boolean_spelling(SWIFT_STDLIB_STATIC_PRINT)

test/lit.site.cfg.in

@@ -143,6 +143,8 @@ if "@SWIFT_STDLIB_ENABLE_UNICODE_DATA" == "TRUE":
     config.available_features.add('stdlib_unicode_data')
 if "@SWIFT_ENABLE_EXPERIMENTAL_STRING_PROCESSING@" == "TRUE":
     config.available_features.add('string_processing')
+if "@SWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE@" == "TRUE":
+    config.available_features.add('swift_stdlib_debug_preconditions_in_release')
 
 config.swift_freestanding_is_darwin = "@SWIFT_FREESTANDING_IS_DARWIN@" == "TRUE"
 config.swift_enable_dispatch = "@SWIFT_ENABLE_DISPATCH@" == "TRUE"

test/stdlib/RangeTraps.swift

@@ -129,7 +129,7 @@ if #available(SwiftStdlib 5.5, *) {
   // Debug check was introduced in https://github.com/apple/swift/pull/34961
   RangeTraps.test("UncheckedHalfOpen")
   .xfail(.custom(
-      { !_isDebugAssertConfiguration() },
+      { !_isStdlibDebugChecksEnabled() },
       reason: "assertions are disabled in Release and Unchecked mode"))
   .code {
     expectCrashLater()
@@ -138,7 +138,7 @@ if #available(SwiftStdlib 5.5, *) {
 
   RangeTraps.test("UncheckedClosed")
   .xfail(.custom(
-      { !_isDebugAssertConfiguration() },
+      { !_isStdlibDebugChecksEnabled() },
       reason: "assertions are disabled in Release and Unchecked mode"))
   .code {
     expectCrashLater()

validation-test/lit.site.cfg.in

@@ -122,6 +122,8 @@ if "@SWIFT_ENABLE_EXPERIMENTAL_DISTRIBUTED@" == "TRUE":
     config.available_features.add('distributed')
 if "@SWIFT_ENABLE_EXPERIMENTAL_STRING_PROCESSING@" == "TRUE":
     config.available_features.add('string_processing')
+if "@SWIFT_STDLIB_ENABLE_DEBUG_PRECONDITIONS_IN_RELEASE@" == "TRUE":
+    config.available_features.add('swift_stdlib_debug_preconditions_in_release')
 
 config.swift_freestanding_is_darwin = "@SWIFT_FREESTANDING_IS_DARWIN@" == "TRUE"
 config.swift_enable_dispatch = "@SWIFT_ENABLE_DISPATCH@" == "TRUE"

validation-test/stdlib/Assert-debugPrecondition-off.swift

@@ -0,0 +1,34 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift %s -Xfrontend -disable-access-control -o %t/Assert_Debug -Onone
+// RUN: %target-build-swift %s -Xfrontend -disable-access-control -o %t/Assert_Release -O
+// RUN: %target-build-swift %s -Xfrontend -disable-access-control -o %t/Assert_Unchecked -Ounchecked
+// RUN: %target-codesign %t/Assert_Debug
+// RUN: %target-codesign %t/Assert_Release
+// RUN: %target-codesign %t/Assert_Unchecked
+// RUN: %target-run %t/Assert_Debug | %FileCheck --check-prefixes=DEBUG %s
+// RUN: %target-run %t/Assert_Release | %FileCheck --check-prefixes=RELEASE %s
+// RUN: %target-run %t/Assert_Unchecked | %FileCheck --check-prefixes=UNCHECKED %s
+
+// UNSUPPORTED: swift_stdlib_debug_preconditions_in_release
+
+// DEBUG: _isStdlibDebugChecksEnabled: true
+// RELEASE: _isStdlibDebugChecksEnabled: false
+// UNCHECKED: _isStdlibDebugChecksEnabled: false
+print("_isStdlibDebugChecksEnabled: \(_isStdlibDebugChecksEnabled())")
+
+
+func check() -> Bool {
+  print("Debug preconditions are active")
+  return true
+}
+
+// DEBUG-NEXT: Debug preconditions are active
+// RELEASE-NOT: Debug preconditions are active
+// UNCHECKED-NOT: Debug preconditions are active
+_debugPrecondition(check()) // Note: side effects in an assert are a terrible
+                            // idea; do not emulate this pattern in real code.
+
+// DEBUG-NEXT: Done
+// RELEASE-NEXT: Done
+// UNCHECKED-NEXT: Done
+print("Done")

validation-test/stdlib/Assert-debugPrecondition-on.swift

@@ -0,0 +1,34 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift %s -Xfrontend -disable-access-control -o %t/Assert_Debug -Onone
+// RUN: %target-build-swift %s -Xfrontend -disable-access-control -o %t/Assert_Release -O
+// RUN: %target-build-swift %s -Xfrontend -disable-access-control -o %t/Assert_Unchecked -Ounchecked
+// RUN: %target-codesign %t/Assert_Debug
+// RUN: %target-codesign %t/Assert_Release
+// RUN: %target-codesign %t/Assert_Unchecked
+// RUN: %target-run %t/Assert_Debug | %FileCheck --check-prefixes=DEBUG %s
+// RUN: %target-run %t/Assert_Release | %FileCheck --check-prefixes=RELEASE %s
+// RUN: %target-run %t/Assert_Unchecked | %FileCheck --check-prefixes=UNCHECKED %s
+
+// REQUIRES: swift_stdlib_debug_preconditions_in_release
+
+// DEBUG: _isStdlibDebugChecksEnabled: true
+// RELEASE: _isStdlibDebugChecksEnabled: true
+// UNCHECKED: _isStdlibDebugChecksEnabled: false
+print("_isStdlibDebugChecksEnabled: \(_isStdlibDebugChecksEnabled())")
+
+
+func check() -> Bool {
+  print("Debug preconditions are active")
+  return true
+}
+
+// DEBUG-NEXT: Debug preconditions are active
+// RELEASE-NEXT: Debug preconditions are active
+// UNCHECKED-NOT: Debug preconditions are active
+_debugPrecondition(check()) // Note: side effects in an assert are a terrible
+                            // idea; do not emulate this pattern in real code.
+
+// DEBUG-NEXT: Done
+// RELEASE-NEXT: Done
+// UNCHECKED-NEXT: Done
+print("Done")

validation-test/stdlib/Assert.swift

@@ -174,10 +174,32 @@ Assert.test("preconditionFailure")
   preconditionFailure("this should fail")
 }
 
+Assert.test("_precondition")
+  .xfail(.custom(
+    { _isFastAssertConfiguration() },
+    reason: "preconditions are disabled in Unchecked mode"))
+  .crashOutputMatches(_isDebugAssertConfiguration() ? "this should fail" : "")
+  .code {
+  var x = 2
+  _precondition(x * 21 == 42, "should not fail")
+  expectCrashLater()
+  _precondition(x == 42, "this should fail")
+}
+
+Assert.test("_preconditionFailure")
+  .skip(.custom(
+    { _isFastAssertConfiguration() },
+    reason: "optimizer assumes that the code path is unreachable"))
+  .crashOutputMatches(_isDebugAssertConfiguration() ? "this should fail" : "")
+  .code {
+  expectCrashLater()
+  _preconditionFailure("this should fail")
+}
+
 Assert.test("_debugPrecondition")
   .xfail(.custom(
-    { !_isDebugAssertConfiguration() },
-    reason: "debug preconditions are disabled in Release and Unchecked mode"))
+    { !_isStdlibDebugChecksEnabled() },
+    reason: "debug preconditions are disabled"))
   .crashOutputMatches(_isDebugAssertConfiguration() ? "this should fail" : "")
   .code {
   var x = 2
@@ -188,9 +210,9 @@ Assert.test("_debugPrecondition")
 
 Assert.test("_debugPreconditionFailure")
   .skip(.custom(
-    { !_isDebugAssertConfiguration() },
+    { !_isStdlibDebugChecksEnabled() },
     reason: "optimizer assumes that the code path is unreachable"))
-  .crashOutputMatches("this should fail")
+  .crashOutputMatches(_isDebugAssertConfiguration() ? "this should fail" : "")
   .code {
   expectCrashLater()
   _debugPreconditionFailure("this should fail")