Revert "Define _GNU_SOURCE and _DEFAULT_SOURCE in the package manifest and cmakefile"

This reverts commit 4801296.

Author: grynspan

Package.swift

@@ -162,13 +162,6 @@ extension Array where Element == PackageDescription.CXXSetting {
   static var packageSettings: Self {
     var result = Self()
 
-    // On platforms that use glibc, define some additional macros to expose some
-    // useful (but non-standard) interfaces.
-    result += [
-      .define("_DEFAULT_SOURCE", to: "1", .when(platforms: [.linux, .custom("FreeBSD"), .android])),
-      .define("_GNU_SOURCE", to: "1", .when(platforms: [.linux, .custom("FreeBSD"), .android])),
-    ]
-
     // Capture the testing library's version as a C++ string constant.
     if let git = Context.gitInformation {
       let testingLibraryVersion = if let tag = git.currentTag {

Sources/Testing/ExitTests/ExitTest.swift

@@ -56,7 +56,7 @@ public struct ExitTest: Sendable {
     // will often be disabled by default.) If a particular Linux distro performs
     // additional crash diagnostics, we may want to special-case them as well if we can.
     var rl = rlimit(rlim_cur: 0, rlim_max: 0)
-    _ = setrlimit(RLIMIT_CORE, &rl)
+    _ = setrlimit(CInt(RLIMIT_CORE.rawValue), &rl)
 #elseif os(Windows)
     // On Windows, similarly disable Windows Error Reporting and the Windows
     // Error Reporting UI. Note we expect to be the first component to call

Sources/Testing/ExitTests/WaitFor.swift

@@ -109,7 +109,7 @@ private let _createWaitThreadImpl: Void = {
 #if SWT_TARGET_OS_APPLE
       _ = pthread_setname_np("Swift Testing exit test monitor")
 #elseif os(Linux)
-      _ = pthread_setname_np(pthread_self(), "SWT ExT monitor")
+      _ = swt_pthread_setname_np(pthread_self(), "SWT ExT monitor")
 #elseif os(FreeBSD)
       _ = pthread_set_name_np(pthread_self(), "SWT ex test monitor")
 #else

Sources/_TestingInternals/Stubs.cpp

@@ -0,0 +1,52 @@
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+//
+
+/// This source file includes implementations of functions that _should_ simply
+/// be `static` stubs in Stubs.h, but which for technical reasons cannot be
+/// imported into Swift when defined in a header.
+///
+/// Do not, as a rule, add function implementations in this file. Prefer to add
+/// them to Stubs.h so that they can be inlined at compile- or link-time. Only
+/// include functions here if Swift cannot successfully import and call them
+/// otherwise.
+
+#if defined(__linux__) || defined(__FreeBSD__)
+#undef _DEFAULT_SOURCE
+#define _DEFAULT_SOURCE 1
+#undef _GNU_SOURCE
+#define _GNU_SOURCE 1
+#endif
+
+#include "Stubs.h"
+
+#include <features.h>
+
+#if defined(__linux__) || defined(__FreeBSD__)
+#endif
+
+#if defined(__linux__)
+int swt_pthread_setname_np(pthread_t thread, const char *name) {
+  return pthread_setname_np(thread, name);
+}
+#endif
+
+#if defined(__linux__) || defined(__FreeBSD__)
+int swt_posix_spawn_file_actions_addclosefrom_np(posix_spawn_file_actions_t *fileActions, int from) {
+  int result = 0;
+
+#if defined(__GLIBC_PREREQ)
+#if __GLIBC_PREREQ(2, 34)
+  result = posix_spawn_file_actions_addclosefrom_np(fileActions, from);
+#endif
+#endif
+
+  return result;
+}
+#endif

Sources/_TestingInternals/include/Stubs.h

@@ -109,22 +109,23 @@ static char *_Nullable *_Null_unspecified swt_environ(void) {
 }
 #endif
 
+#if defined(__linux__)
+/// Set the name of the current thread.
+///
+/// This function declaration is provided because `pthread_setname_np()` is
+/// only declared if `_GNU_SOURCE` is set, but setting it causes build errors
+/// due to conflicts with Swift's Glibc module.
+SWT_EXTERN int swt_pthread_setname_np(pthread_t thread, const char *name);
+#endif
+
 #if defined(__linux__) || defined(__FreeBSD__)
 /// Close file descriptors above a given value when spawing a new process.
 ///
 /// This symbol is provided because the underlying function was added to glibc
-/// relatively recently and may not be available on all targets.
-static int swt_posix_spawn_file_actions_addclosefrom_np(posix_spawn_file_actions_t *fileActions, int from) {
-  int result = 0;
-
-#if defined(__GLIBC_PREREQ)
-#if __GLIBC_PREREQ(2, 34)
-  result = posix_spawn_file_actions_addclosefrom_np(fileActions, from);
-#endif
-#endif
-
-  return result;
-}
+/// relatively recently and may not be available on all targets. Checking
+/// `__GLIBC_PREREQ()` is insufficient because `_DEFAULT_SOURCE` may not be
+/// defined at the point spawn.h is first included.
+SWT_EXTERN int swt_posix_spawn_file_actions_addclosefrom_np(posix_spawn_file_actions_t *fileActions, int from);
 #endif
 
 #if !defined(__ANDROID__)

cmake/modules/shared/CompilerSettings.cmake

@@ -16,11 +16,6 @@ add_compile_options(
   "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-upcoming-feature -Xfrontend ExistentialAny>"
   "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-upcoming-feature -Xfrontend InternalImportsByDefault>")
 
-set(SWT_GLIBC "Linux" "FreeBSD" "Android")
-if(CMAKE_SYSTEM_NAME IN_LIST SWT_GLIBC)
-add_compile_definitions("_DEFAULT_SOURCE" "_GNU_SOURCE")
-endif()
-
 # Platform-specific definitions.
 if(APPLE)
   add_compile_definitions("SWT_TARGET_OS_APPLE")