From 50678d0942ae77c618d597dc3fec28cde5824e71 Mon Sep 17 00:00:00 2001
From: Rangi <sylvie.oukaour+rangi42@gmail.com>
Date: Tue, 21 Jul 2026 14:38:14 -0400
Subject: [PATCH] Use `_fseeki64`/`_ftelli64` on Windows since `fseek`/`fell`
 are limited by 32-bit `long`

---
 include/platform.hpp | 6 ++++++
 src/asm/section.cpp  | 3 ++-
 src/util.cpp         | 2 +-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/platform.hpp b/include/platform.hpp
index 5b64a572..7c20c9c1 100644
--- a/include/platform.hpp
+++ b/include/platform.hpp
@@ -55,6 +55,12 @@
 	#define setmode(fd, mode) (0)
 #endif
 
+// Windows has 32-bit `long`, which limits `fseek` and `ftell` to 2 GiB
+#if defined(_MSC_VER) || defined(__MINGW32__)
+	#define fseek _fseeki64
+	#define ftell _ftelli64
+#endif
+
 // MingGW and Cygwin need POSIX functions which are not standard C explicitly enabled,
 #if defined(__MINGW32__) || defined(__CYGWIN__)
 	#define _POSIX_C_SOURCE 200809L
diff --git a/src/asm/section.cpp b/src/asm/section.cpp
index e5c6d49f..c9723f58 100644
--- a/src/asm/section.cpp
+++ b/src/asm/section.cpp
@@ -21,7 +21,8 @@
 #include "helpers.hpp"
 #include "itertools.hpp" // InsertionOrderedMap
 #include "linkdefs.hpp"
-#include "util.hpp" // xfclose, seekSize
+#include "platform.hpp" // fseek
+#include "util.hpp"     // xfclose, seekSize
 
 #include "asm/fstack.hpp"
 #include "asm/lexer.hpp"
diff --git a/src/util.cpp b/src/util.cpp
index 5384107a..48d73f8a 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -29,7 +29,7 @@ std::optional<uint64_t> seekSize(FILE *file) {
 	if (fseek(file, 0, SEEK_END) != 0) {
 		return std::nullopt;
 	}
-	long size = ftell(file);
+	auto size = ftell(file); // Use `auto` since Windows' `_ftelli64` returns `__int64`, not `long`
 	if (size < 0) {
 		return std::nullopt;
 	}