[libcxx-commits] [libcxx] [libc++] Optimize std::print for Windows 8+ (PR #232993)

[Martin Storsjö via libcxx-commits]

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@@ -37,18 +40,52 @@ _LIBCPP_BEGIN_EXPLICIT_ABI_ANNOTATIONS
 
 #ifdef _WIN32
 
-_LIBCPP_EXPORTED_FROM_ABI bool __is_windows_terminal(FILE* __stream) {
+using NtQueryVolumeInformationFileType = NTSTATUS
+    NTAPI(HANDLE handle, PIO_STATUS_BLOCK ioStatus, PVOID information, ULONG length, ULONG informationClass);
+
+// https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/ns-wdm-_file_fs_device_information
+struct FILE_FS_DEVICE_INFORMATION {
+  DEVICE_TYPE DeviceType;
+  ULONG Characteristics;
+};
+
+// https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/ne-wdm-_fsinfoclass
+#  define FileFsDeviceInformation 4
+
+static NtQueryVolumeInformationFileType* __get_NtQVIF_win8_or_greater() {
+  // Windows 7 does not support querying the device type of a console handle, so returning nullptr indicates that this
+  // approach is not supported.
+  if (!IsWindows8OrGreater())
+    return nullptr;
+  return (NtQueryVolumeInformationFileType*)GetProcAddress(
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mstorsjo wrote:

IIRC it's not strictly well defined what happens if you pass `NULL` to `GetProcAddress` (if `GetModuleHandleW` fails). In practice it's fine, but if possible it's nicer if we can check the return value of `GetModuleHandleW` before, too.

https://github.com/llvm/llvm-project/pull/232993