Add SWIFT_STDLIB_HAS_ENVIRON to remove usage of getenv/environ from stdlib (#39599)

Author: kubamracek

stdlib/CMakeLists.txt

@@ -111,6 +111,10 @@ option(SWIFT_STDLIB_HAS_STDIN
        "Build stdlib assuming the platform supports stdin and getline API."
        TRUE)
 
+option(SWIFT_STDLIB_HAS_ENVIRON
+       "Build stdlib assuming the platform supports environment variables."
+       TRUE)
+
 option(SWIFT_STDLIB_SINGLE_THREADED_RUNTIME
        "Build the standard libraries assuming that they will be used in an environment with only a single thread."
        FALSE)

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -343,6 +343,10 @@ function(_add_target_variant_c_compile_flags)
     list(APPEND result "-DSWIFT_STDLIB_HAS_STDIN")
   endif()
 
+  if(SWIFT_STDLIB_HAS_ENVIRON)
+    list(APPEND result "-DSWIFT_STDLIB_HAS_ENVIRON")
+  endif()
+
   if(SWIFT_STDLIB_SINGLE_THREADED_RUNTIME)
     list(APPEND result "-DSWIFT_STDLIB_SINGLE_THREADED_RUNTIME")
   endif()

stdlib/cmake/modules/SwiftSource.cmake

@@ -293,6 +293,11 @@ function(_add_target_variant_swift_compile_flags
     list(APPEND result "-D" "SWIFT_STDLIB_HAS_STDIN")
   endif()
 
+  if(SWIFT_STDLIB_HAS_ENVIRON)
+    list(APPEND result "-D" "SWIFT_STDLIB_HAS_ENVIRON")
+    list(APPEND result "-Xcc" "-DSWIFT_STDLIB_HAS_ENVIRON")
+  endif()
+
   set("${result_var_name}" "${result}" PARENT_SCOPE)
 endfunction()
 

stdlib/private/SwiftPrivateLibcExtras/CMakeLists.txt

@@ -1,3 +1,8 @@
+set(swift_private_libc_extras_flags)
+if(SWIFT_STDLIB_HAS_ENVIRON)
+  set(swift_private_libc_extras_flags "-D" "SWIFT_STDLIB_HAS_ENVIRON")
+endif()
+
 add_swift_target_library(swiftSwiftPrivateLibcExtras ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB
   # This file should be listed the first.  Module name is inferred from the
   # filename.
@@ -8,7 +13,7 @@ add_swift_target_library(swiftSwiftPrivateLibcExtras ${SWIFT_STDLIB_LIBRARY_BUIL
   "${SWIFT_SOURCE_DIR}/stdlib/linker-support/magic-symbols-for-install-name.c"
 
   SWIFT_MODULE_DEPENDS SwiftPrivate
-  SWIFT_COMPILE_FLAGS ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
+  SWIFT_COMPILE_FLAGS ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS} ${swift_private_libc_extras_flags}
   SWIFT_MODULE_DEPENDS_OSX Darwin
   SWIFT_MODULE_DEPENDS_IOS Darwin
   SWIFT_MODULE_DEPENDS_TVOS Darwin

stdlib/private/SwiftPrivateLibcExtras/Subprocess.swift

@@ -213,6 +213,23 @@ func posixPipe() -> (readFD: CInt, writeFD: CInt) {
   return (fds[0], fds[1])
 }
 
+#if !SWIFT_STDLIB_HAS_ENVIRON
+@_silgen_name("_NSGetEnviron")
+func _NSGetEnviron() -> UnsafeMutablePointer<UnsafeMutablePointer<UnsafeMutablePointer<CChar>?>>
+
+var environ: UnsafeMutablePointer<UnsafeMutablePointer<CChar>?> {
+  #if os(macOS)
+  return _NSGetEnviron().pointee
+  #elseif os(Windows)
+  return __p_environ().pointee
+  #elseif os(Linux)
+  return __environ
+  #else
+  #error("unsupported platform")
+  #endif
+}
+#endif
+
 /// Start the same executable as a child process, redirecting its stdout and
 /// stderr.
 public func spawnChild(_ args: [String])

stdlib/public/Platform/Platform.swift

@@ -427,6 +427,7 @@ public func sem_open(
 //===----------------------------------------------------------------------===//
 
 // Some platforms don't have `extern char** environ` imported from C.
+#if SWIFT_STDLIB_HAS_ENVIRON
 #if os(macOS) || os(iOS) || os(watchOS) || os(tvOS) || os(FreeBSD) || os(OpenBSD) || os(PS4)
 public var environ: UnsafeMutablePointer<UnsafeMutablePointer<CChar>?> {
   return _swift_stdlib_getEnviron()
@@ -436,3 +437,4 @@ public var environ: UnsafeMutablePointer<UnsafeMutablePointer<CChar>?> {
   return __environ
 }
 #endif
+#endif // SWIFT_STDLIB_HAS_ENVIRON

stdlib/public/SwiftShims/LibcOverlayShims.h

@@ -52,6 +52,7 @@ static inline int _swift_stdlib_fcntlPtr(int fd, int cmd, void* ptr) {
 #endif
 
 // Environment
+#if SWIFT_STDLIB_HAS_ENVIRON
 #if defined(__FreeBSD__) || defined(__OpenBSD__)
 static inline char * _Nullable * _Null_unspecified _swift_stdlib_getEnviron() {
   extern char **environ;
@@ -63,6 +64,7 @@ static inline char * _Nullable *_swift_stdlib_getEnviron() {
   return *_NSGetEnviron();
 }
 #endif
+#endif  // SWIFT_STDLIB_HAS_ENVIRON
 
 // System error numbers <errno.h>
 static inline int _swift_stdlib_getErrno() {

stdlib/public/runtime/EnvironmentVariables.cpp

@@ -35,6 +35,8 @@ static constexpr bool hasSwiftPrefix(const char *str) {
   static_assert(hasSwiftPrefix(#name), "Names must start with SWIFT");
 #include "EnvironmentVariables.def"
 
+#if SWIFT_STDLIB_HAS_ENVIRON
+
 // Value parsers. Add new functions named parse_<type> to accommodate more
 // debug variable types.
 static bool parse_bool(const char *name, const char *value, bool defaultValue) {
@@ -108,6 +110,8 @@ void printHelp(const char *extra) {
   swift::warning(RuntimeErrorFlagNone, "SWIFT_DEBUG_HELP=YES - Print this help.");
 }
 
+#endif  // SWIFT_STDLIB_HAS_ENVIRON
+
 } // end anonymous namespace
 
 // Define backing variables.
@@ -118,7 +122,7 @@ void printHelp(const char *extra) {
 // Initialization code.
 OnceToken_t swift::runtime::environment::initializeToken;
 
-#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__linux__)
+#if SWIFT_STDLIB_HAS_ENVIRON && (defined(__APPLE__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__linux__))
 extern "C" char **environ;
 #define ENVIRON environ
 #elif defined(_WIN32)
@@ -184,7 +188,7 @@ void swift::runtime::environment::initialize(void *context) {
   if (SWIFT_DEBUG_HELP_variable)
     printHelp(nullptr);
 }
-#else
+#elif SWIFT_STDLIB_HAS_ENVIRON
 void swift::runtime::environment::initialize(void *context) {
   // Emit a getenv call for each variable. This is less efficient but works
   // everywhere.
@@ -197,6 +201,10 @@ void swift::runtime::environment::initialize(void *context) {
     printHelp("Using getenv to read variables. Unknown SWIFT_DEBUG_ variables "
               "will not be flagged.");
 }
+#else
+void swift::runtime::environment::initialize(void *context) {
+  (void)context;
+}
 #endif
 
 SWIFT_RUNTIME_EXPORT

utils/build-presets.ini

@@ -2468,6 +2468,7 @@ swift-stdlib-supports-backtrace-reporting=0
 swift-stdlib-has-darwin-libmalloc=0
 swift-stdlib-has-asl=0
 swift-stdlib-has-stdin=0
+swift-stdlib-has-environ=0
 swift-runtime-static-image-inspection=1
 swift-stdlib-single-threaded-runtime=1
 swift-stdlib-os-versioning=0

utils/build-script-impl

@@ -215,6 +215,7 @@ KNOWN_SETTINGS=(
     swift-stdlib-has-darwin-libmalloc             "1"               "whether the Darwin build of stdlib can use extended libmalloc APIs"
     swift-stdlib-has-asl                          ""                "whether the stdlib can use the asl_log API, defaults to true on Darwin, false otherwise"
     swift-stdlib-has-stdin                        "1"               "whether to build stdlib assuming the platform supports stdin and getline API"
+    swift-stdlib-has-environ                      "1"               "whether to build stdlib assuming the platform supports environment variables"
     swift-stdlib-lto                              ""                "enable LLVM LTO on the stdlib, valid values are empty string (no LTO), 'full' and 'thin'"
     swift-disable-dead-stripping                  "0"               "turns off Darwin-specific dead stripping for Swift host tools"
     common-swift-flags                            ""                "Flags used for Swift targets other than the stdlib, like the corelibs"
@@ -1991,6 +1992,7 @@ for host in "${ALL_HOSTS[@]}"; do
                     -DSWIFT_STDLIB_OS_VERSIONING:BOOL=$(true_false "${SWIFT_STDLIB_OS_VERSIONING}")
                     -DSWIFT_STDLIB_HAS_DARWIN_LIBMALLOC:BOOL=$(true_false "${SWIFT_STDLIB_HAS_DARWIN_LIBMALLOC}")
                     -DSWIFT_STDLIB_HAS_STDIN:BOOL=$(true_false "${SWIFT_STDLIB_HAS_STDIN}")
+                    -DSWIFT_STDLIB_HAS_ENVIRON:BOOL=$(true_false "${SWIFT_STDLIB_HAS_ENVIRON}")
                     -DSWIFT_STDLIB_ENABLE_LTO:STRING="${SWIFT_STDLIB_LTO}"
                     -DSWIFT_NATIVE_LLVM_TOOLS_PATH:STRING="${native_llvm_tools_path}"
                     -DSWIFT_NATIVE_CLANG_TOOLS_PATH:STRING="${native_clang_tools_path}"

utils/check_freestanding_dependencies.py

@@ -51,7 +51,7 @@
 common_expected_dependencies = [
     "___bzero", "___divti3", "___error", "___stderrp", "___stdoutp",
     "___truncsfhf2", "___udivti3", "_abort", "_arc4random_buf",
-    "_calloc", "_close", "_environ", "_flockfile", "_floorl", "_fprintf",
+    "_calloc", "_close", "_flockfile", "_floorl", "_fprintf",
     "_fputc", "_fputs", "_free", "_funlockfile", "_fwrite", "_malloc",
     "_malloc_size", "_memchr", "_memcmp", "_memcpy", "_memmove", "_memset",
     "_posix_memalign", "_putc", "_read", "_realloc", "_snprintf", "_strchr",

validation-test/stdlib/Hashing.swift

@@ -1,6 +1,9 @@
 // RUN: %target-run-stdlib-swift
 // REQUIRES: executable_test
 
+// Freestanding doesn't support environment variables, and this test depends on SWIFT_DETERMINISTIC_HASHING=1
+// UNSUPPORTED: freestanding
+
 import Swift
 import SwiftPrivate
 import StdlibUnittest

validation-test/stdlib/HashingRandomization.swift

@@ -10,6 +10,9 @@
 
 // REQUIRES: executable_test
 
+// Freestanding doesn't support environment variables, and this test depends on SWIFT_DETERMINISTIC_HASHING=1
+// UNSUPPORTED: freestanding
+
 // This check verifies that the hash seed is randomly generated on every
 // execution of a Swift program unless the SWIFT_DETERMINISTIC_HASHING
 // environment variable is set.