[libcxx-commits] [libcxx] [libcxx] Use _ftelli64/_fseeki64 on Windows (PR #123128)

[Martin Storsjö via libcxx-commits]

https://github.com/mstorsjo created https://github.com/llvm/llvm-project/pull/123128

This allows using the full 64 bit range for file offsets.

This should fix the issue reported downstream at
https://github.com/mstorsjo/llvm-mingw/issues/462.

>From eec1f0c6e22145cedbad4b346bc6892b62e478af Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin at martin.st>
Date: Sat, 11 Jan 2025 17:16:41 +0200
Subject: [PATCH] [libcxx] Use _ftelli64/_fseeki64 on Windows

This allows using the full 64 bit range for file offsets.

This should fix the issue reported downstream at
https://github.com/mstorsjo/llvm-mingw/issues/462.
---
 libcxx/include/fstream                                | 11 +++++++++--
 .../fstreams/ifstream.members/offset_range.pass.cpp   |  6 ------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/libcxx/include/fstream b/libcxx/include/fstream
index f0e9425e0a53d99..b6f7f0439c566ab 100644
--- a/libcxx/include/fstream
+++ b/libcxx/include/fstream
@@ -936,7 +936,11 @@ basic_filebuf<_CharT, _Traits>::seekoff(off_type __off, ios_base::seekdir __way,
   default:
     return pos_type(off_type(-1));
   }
-#    if !_LIBCPP_HAS_OFF_T_FUNCTIONS
+#    if defined(_LIBCPP_MSVCRT_LIKE)
+  if (_fseeki64(__file_, __width > 0 ? __width * __off : 0, __whence))
+    return pos_type(off_type(-1));
+  pos_type __r = _ftelli64(__file_);
+#    elif !_LIBCPP_HAS_OFF_T_FUNCTIONS
   if (fseek(__file_, __width > 0 ? __width * __off : 0, __whence))
     return pos_type(off_type(-1));
   pos_type __r = ftell(__file_);
@@ -954,7 +958,10 @@ typename basic_filebuf<_CharT, _Traits>::pos_type
 basic_filebuf<_CharT, _Traits>::seekpos(pos_type __sp, ios_base::openmode) {
   if (__file_ == nullptr || sync())
     return pos_type(off_type(-1));
-#    if !_LIBCPP_HAS_OFF_T_FUNCTIONS
+#    if defined(_LIBCPP_MSVCRT_LIKE)
+  if (_fseeki64(__file_, __sp, SEEK_SET))
+    return pos_type(off_type(-1));
+#    elif !_LIBCPP_HAS_OFF_T_FUNCTIONS
   if (fseek(__file_, __sp, SEEK_SET))
     return pos_type(off_type(-1));
 #    else
diff --git a/libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/offset_range.pass.cpp b/libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/offset_range.pass.cpp
index 5afd4465db31e07..ca6c609c7be312f 100644
--- a/libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/offset_range.pass.cpp
+++ b/libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/offset_range.pass.cpp
@@ -11,12 +11,6 @@
 // Test that we can seek using offsets larger than 32 bit, and that we can
 // retrieve file offsets larger than 32 bit.
 
-// On MSVC targets, we only use the 32 bit fseek/ftell functions. For MinGW
-// targets, we use fseeko/ftello, but the user needs to define
-// _FILE_OFFSET_BITS=64 to make them 64 bit.
-//
-// XFAIL: target={{.*}}-windows{{.*}}
-
 // On 32 bit Android platforms, off_t is 32 bit by default. By defining
 // _FILE_OFFSET_BITS=64, one gets a 64 bit off_t, but the corresponding
 // 64 bit ftello/fseeko functions are only available since Android API 24 (7.0).