[PATCH v4] libio: Properly link in function _IO_wfile_doallocate in static binaries

[yunzezhu@linux.alibaba.com]

From: Yunze Zhu <yunzezhu@linux.alibaba.com>

Changes from V3:
Combine tests-static tests in Makefile.

Changes from V2:
Fix no newline at end of file error in tst-wfiledoallocate-static.
Put test tst-wfiledoallocate-static in Makefile into a new line.

Changes from V1:
Add a simple testcase that triggers Bug #33935.

This patch addresses Bug 33935 - _IO_wfile_doallocate not linked correctly
when linking glibc statically.
https://sourceware.org/bugzilla/show_bug.cgi?id=33935

The function _IO_wfile_doallocate has been added with pragma weak in vtable.c,
while it is the only one symbol contained in wfiledoalloc.c,
and has not been directly called in libio.

In static binaries the true function symbol _IO_wfile_doallocate may not
be correctly linked when linking glibc with cases contains wchar functions,
but the weak symbol in vtable is linked instead,
and cause segmentation fault when running.

This patch fixes this with similar way to symbol _IO_file_doallocate,
that add libio_static_fn_required(_IO_wfile_doallocate) in wgenops.c
to make _IO_wfile_doallocate always link in static binaries.
---
 libio/Makefile                     |  6 +++++-
 libio/tst-wfiledoallocate-static.c | 29 +++++++++++++++++++++++++++++
 libio/wgenops.c                    |  2 ++
 3 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 libio/tst-wfiledoallocate-static.c

diff --git a/libio/Makefile b/libio/Makefile
index 4f4dd9f275..08e1e0ec25 100644
--- a/libio/Makefile
+++ b/libio/Makefile
@@ -136,6 +136,7 @@ tests = \
   tst-ungetwc1 \
   tst-ungetwc2 \
   tst-wfile-sync \
+  tst-wfiledoallocate-static \
   tst-widetext \
   tst-wmemstream1 \
   tst-wmemstream2 \
@@ -151,7 +152,10 @@ tests = \
   tst_wscanf \
   # tests
 
-tests-static += tst-stdio-static
+tests-static += \
+   tst-stdio-static \
+   tst-wfiledoallocate-static \
+# tests-static
 
 $(objpfx)tst-popen-fork: $(shared-thread-library)
 
diff --git a/libio/tst-wfiledoallocate-static.c b/libio/tst-wfiledoallocate-static.c
new file mode 100644
index 0000000000..8cdba1bf75
--- /dev/null
+++ b/libio/tst-wfiledoallocate-static.c
@@ -0,0 +1,29 @@
+/* Test static link with function _IO_wfile_doallocate.
+   Copyright (C) 2026 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <wchar.h>
+
+/* NB: Call main directly to trigger BZ #33935.  */
+
+int main()
+{
+	const wchar_t *string = L"Test String.";
+	int res = wprintf(L"%ls\n", string);
+        return 0;
+}
diff --git a/libio/wgenops.c b/libio/wgenops.c
index 7a8466ea44..064d71266d 100644
--- a/libio/wgenops.c
+++ b/libio/wgenops.c
@@ -34,6 +34,8 @@
 
 static int save_for_wbackup (FILE *fp, wchar_t *end_p) __THROW;
 
+libio_static_fn_required (_IO_wfile_doallocate);
+
 /* Return minimum _pos markers
    Assumes the current get area is the main get area. */
 ssize_t
-- 
2.47.1