[PATCH 0/1] MR7594: msvcrt: Add _IONBF flag check in _filbuf to avoid dead loop in application which sets the flag.

[Kun Yang (＠yangkun)]

Signed-off-by: Kun Yang <yangkun(a)uniontech.com>
Change-Id: Ia68e11ccb0aa563eeb73a2f5cb93afcd328e1937

[fgetws_test.7z](/uploads/7b706f2c4f639e4260c548d834658b32/fgetws_test.7z)
If the application calls setvbuf(.., _IONBF, ..) before fgetws, wine sets the flag. In fgetws, this flag is not checked. read_i is called with paramenter count 1 which is not allowed in read_i implemantion. Function read_i returns -1 and the file stream is not actually read by program. The file pointer is not moved. If the application writes fgetws in a loop, it never reach EOF and falls in dead loop. By adding check for _IONBF in _filbuf, the application will run into another branch(file->_bufsiz=2). Thats's correct. Please checkout the example in my attachment. This application exits normally in Windows but falls in dead loop in wine.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/7594

[PATCH 1/1] msvcrt: Add _IONBF flag check in _filbuf to avoid dead loop in application which sets the flag.

[Kun Yang]

From: Kun Yang <yangkun(a)uniontech.com>

Signed-off-by: Kun Yang <yangkun(a)uniontech.com>
Change-Id: Ia68e11ccb0aa563eeb73a2f5cb93afcd328e1937
---
 dlls/msvcrt/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dlls/msvcrt/file.c b/dlls/msvcrt/file.c
index dda12a70194..38b422b2fab 100644
--- a/dlls/msvcrt/file.c
+++ b/dlls/msvcrt/file.c
@@ -3834,7 +3834,7 @@ int CDECL _filbuf(FILE* file)
             return EOF;
     }
 
-    if(!(file->_flag & (_IOMYBUF | MSVCRT__USERBUF))) {
+    if(!(file->_flag & (_IONBF | _IOMYBUF | MSVCRT__USERBUF))) {
         int r;
         if ((r = _read(file->_file,&c,1)) != 1) {
             file->_flag |= (r == 0) ? _IOEOF : _IOERR;
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/7594