[PATCH 0/1] MR7312: msvcp: Avoid explicitly aligning fpos_mbstatet.

[Jacek Caban (＠jacek)]

Based on Piotr's findings.

On MSVC i386 targets, structs requiring alignment greater than 4 are never passed by value.
Clang follows the same behavior in MSVC mode (see [1] for details and [2] for a follow-up
that applies this logic when fields, not necessarily the entire struct, are aligned).

A number of ios functions take fpos_mbstatet as an argument and expect it to be passed by value.

[1] https://reviews.llvm.org/D72114
[2] https://github.com/llvm/llvm-project/issues/63257

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=57817

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https://gitlab.winehq.org/wine/wine/-/merge_requests/7312

[PATCH 1/1] msvcp: Avoid explicitly aligning fpos_mbstatet.

[Jacek Caban]

From: Jacek Caban <jacek(a)codeweavers.com>

Based on Piotr's findings.

On MSVC i386 targets, structs requiring alignment greater than 4 are never passed by value.
Clang follows the same behavior in MSVC mode (see [1] for details and [2] for a follow-up
that applies this logic when fields, not necessarily the entire struct, are aligned).

A number of ios functions take fpos_mbstatet as an argument and expect it to be passed by value.

[1] https://reviews.llvm.org/D72114
[2] https://github.com/llvm/llvm-project/issues/63257

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=57817
---
 dlls/msvcp90/ios.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dlls/msvcp90/ios.c b/dlls/msvcp90/ios.c
index cb3e7573283..d7f25b559a8 100644
--- a/dlls/msvcp90/ios.c
+++ b/dlls/msvcp90/ios.c
@@ -41,7 +41,7 @@ bool ios_base_Sync = FALSE;
 
 typedef struct {
     streamoff off;
-    __int64 DECLSPEC_ALIGN(8) pos;
+    INT64 pos;
     _Mbstatet state;
 } fpos_mbstatet;
 
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/7312

[Piotr Caban (＠piotr)]

Piotr Caban (@piotr) commented about dlls/msvcp90/ios.c:
> typedef struct {
>      streamoff off;

It doesn't work for newer versions of msvcp. `streamoff` and `streamsize` definition in `msvcp90.h` also needs to be fixed.

Could you please also add similar change to msvcp60/ios.c?

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/7312#note_94347