[SYCL] Remove some OSUtil::* funcs from ABI under -fpreview-breaking-changes (#16177)

These are used internally in the DSO and don't need to be exposed
outside.

`OSUtil::getDirName` will become `static` inside single TU under the
`-fpreview-breaking-changes` flag and `private` for the time being
without the flag (to make sure no new uses will be added outside the
TU).

`OSUtil::getCurrentDSODir` is used in several TUs, so simply make it
`__SYCL_DLL_LOCAL` to remove from exported symbols during the next
ABI-breaking window.

Author: aelovikov-intel

sycl/include/sycl/detail/os_util.hpp

@@ -42,12 +42,22 @@ namespace detail {
 
 /// Groups the OS-dependent services.
 class __SYCL_EXPORT OSUtil {
+#if !defined(__INTEL_PREVIEW_BREAKING_CHANGES)
+#ifdef _WIN32
+  // Access control is part of the mangling on Windows, have to preserve this
+  // for backward ABI compatibility.
 public:
-  /// Returns an absolute path to a directory where the object was found.
-  static std::string getCurrentDSODir();
-
+#endif
   /// Returns a directory component of a path.
   static std::string getDirName(const char *Path);
+#endif
+
+public:
+  /// Returns an absolute path to a directory where the object was found.
+#if defined(__INTEL_PREVIEW_BREAKING_CHANGES)
+  __SYCL_DLL_LOCAL
+#endif
+  static std::string getCurrentDSODir();
 
 #ifdef __SYCL_RT_OS_WINDOWS
   static constexpr const char *DirSep = "\\";

sycl/source/detail/os_util.cpp

@@ -69,6 +69,20 @@ bool procMapsAddressInRange(std::istream &Stream, uintptr_t Addr) {
   return Addr >= Start && Addr < End;
 }
 
+#if defined(__INTEL_PREVIEW_BREAKING_CHANGES)
+static std::string getDirName(const char *Path)
+#else
+std::string OSUtil::getDirName(const char *Path)
+#endif
+{
+  std::string Tmp(Path);
+  // dirname(3) needs a writable C string: a null-terminator is written where a
+  // path should split.
+  size_t TruncatedSize = strlen(dirname(const_cast<char *>(Tmp.c_str())));
+  Tmp.resize(TruncatedSize);
+  return Tmp;
+}
+
 /// Returns an absolute path to a directory where the object was found.
 std::string OSUtil::getCurrentDSODir() {
   // Examine /proc/self/maps and find where this function (getCurrendDSODir)
@@ -130,21 +144,12 @@ std::string OSUtil::getCurrentDSODir() {
     char Path[PATH_MAX];
     Stream.getline(Path, PATH_MAX - 1);
     Path[PATH_MAX - 1] = '\0';
-    return OSUtil::getDirName(Path);
+    return getDirName(Path);
   }
   assert(false && "Unable to find the current function in /proc/self/maps");
   return "";
 }
 
-std::string OSUtil::getDirName(const char *Path) {
-  std::string Tmp(Path);
-  // dirname(3) needs a writable C string: a null-terminator is written where a
-  // path should split.
-  size_t TruncatedSize = strlen(dirname(const_cast<char *>(Tmp.c_str())));
-  Tmp.resize(TruncatedSize);
-  return Tmp;
-}
-
 #elif defined(__SYCL_RT_OS_WINDOWS)
 
 /// Returns an absolute path where the object was found.
@@ -169,6 +174,7 @@ std::string OSUtil::getCurrentDSODir() {
   return Path;
 }
 
+#if !defined(__INTEL_PREVIEW_BREAKING_CHANGES)
 std::string OSUtil::getDirName(const char *Path) {
   std::string Tmp(Path);
   // Remove trailing directory separators
@@ -181,6 +187,7 @@ std::string OSUtil::getDirName(const char *Path) {
   // If no directory separator is present return initial path like dirname does
   return Tmp;
 }
+#endif
 
 #elif defined(__SYCL_RT_OS_DARWIN)
 std::string OSUtil::getCurrentDSODir() {

sycl/source/detail/persistent_device_code_cache.hpp

@@ -24,10 +24,6 @@ namespace sycl {
 inline namespace _V1 {
 namespace detail {
 
-/* This is temporary solution until std::filesystem is available when SYCL RT
- * is moved to c++17 standard*/
-std::string getDirName(const char *Path);
-
 /* The class manages inter-process synchronization:
  *  - Path passed to the constructor is appended with .lock and used as lock
  *    file.

sycl/tools/sycl-trace/collector.cpp

@@ -18,7 +18,7 @@ sycl::detail::SpinLock GlobalLock;
 
 bool HasZEPrinter = false;
 
-std::string getCurrentDSODir() {
+static std::string getCurrentDSODir() {
   auto CurrentFunc = reinterpret_cast<const void *>(&getCurrentDSODir);
   Dl_info Info;
   int RetCode = dladdr(CurrentFunc, &Info);

sycl/ur_win_proxy_loader/ur_win_proxy_loader.cpp

@@ -65,7 +65,7 @@ static OSModuleHandle getOSModuleHandle(const void *VirtAddr) {
 
 // cribbed from sycl/source/detail/os_util.cpp
 /// Returns an absolute path where the object was found.
-std::wstring getCurrentDSODir() {
+static std::wstring getCurrentDSODir() {
   wchar_t Path[MAX_PATH];
   auto Handle = getOSModuleHandle(reinterpret_cast<void *>(&getCurrentDSODir));
   DWORD Ret = GetModuleFileName(