From: Viktor Szakats <commit@vsz.me>
Date: Mon, 5 Jan 2026 10:04:10 +0000 (+0100)
Subject: curlx_win32_fopen: use `_fsopen()`/`_wfsopen()` with `_SH_DENYNO`
X-Git-Tag: curl-8_18_0~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e2d61a6b306cece5f194d70c05e55352f525dff9;p=thirdparty%2Fcurl.git

curlx_win32_fopen: use `_fsopen()`/`_wfsopen()` with `_SH_DENYNO`

Replacing `fopen_s()`/`_wfopen_s()`, to allow customizing share mode,
and keep the sharing mode as was with `fopen()`/`_wopen()` earlier and
as used in `_sopen_s()`/`_wsopen_s()`.

The replaced functions used `_SH_SECURE` internally. Otherwise they are
identical to the replacements.

Ref: https://learn.microsoft.com/cpp/c-runtime-library/reference/fsopen-wfsopen

Reported-by: Jay Satiro
Fixes #20155
Ref: #20156
Follow-up to 1e7d0bafc6d25d98ec72ff419df65fda3cf147a7 #19643
Closes #20186
---

diff --git a/lib/curlx/fopen.c b/lib/curlx/fopen.c
index 035632af4b..e9eb6df3b0 100644
--- a/lib/curlx/fopen.c
+++ b/lib/curlx/fopen.c
@@ -348,7 +348,7 @@ FILE *curlx_win32_fopen(const char *filename, const char *mode)
       target = fixed;
     else
       target = filename_w;
-    errno = _wfopen_s(&result, target, mode_w);
+    result = _wfsopen(target, mode_w, _SH_DENYNO);
   }
   else
     /* !checksrc! disable ERRNOVAR 1 */
@@ -360,7 +360,7 @@ FILE *curlx_win32_fopen(const char *filename, const char *mode)
     target = fixed;
   else
     target = filename;
-  errno = fopen_s(&result, target, mode);
+  result = _fsopen(target, mode, _SH_DENYNO);
 #endif
 
   CURLX_FREE(fixed);