[PATCH 0/2] Fix Windows build issues with newer MinGW

[PATCH 0/2] Fix Windows build issues with newer MinGW

[phind.uet]

From: Nguyen Dinh Phi <phind.uet@gmail.com>

This series fixes build issues when compiling QEMU on Windows with
newer MinGW-w64 toolchains.

Patch 1 addresses a redefinition error for ConvertStringToBSTR(),
which is now provided by newer MinGW versions in <comutil.h>.

Patch 2 relocates qemu_ftruncate64() to a more appropriate location.

Nguyen Dinh Phi (2):
  qga/vss-win32: Fix ConvertStringToBSTR redefinition with newer MinGW
  util: Move qemu_ftruncate64 from block/file-win32.c to oslib-win32.c

 block/file-win32.c        | 32 --------------------------------
 meson.build               | 12 ++++++++++++
 qga/vss-win32/install.cpp |  2 ++
 util/oslib-win32.c        | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 48 insertions(+), 32 deletions(-)

-- 
2.43.0

[PATCH 1/2] qga/vss-win32: Fix ConvertStringToBSTR redefinition with newer MinGW

[phind.uet]

From: Nguyen Dinh Phi <phind.uet@gmail.com>

Newer versions of MinGW-w64 provide ConvertStringToBSTR() in the
_com_util namespace via <comutil.h>. This causes a redefinition
error when building qemu-ga on Windows with these toolchains.

Add a meson check to detect whether ConvertStringToBSTR is already
available, and conditionally compile our fallback implementation
only when the system does not provide one.

Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
---
 meson.build               | 12 ++++++++++++
 qga/vss-win32/install.cpp |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/meson.build b/meson.build
index c5710a6a47..60a980e610 100644
--- a/meson.build
+++ b/meson.build
@@ -3299,6 +3299,18 @@ endif
 # Detect host pointer size for the target configuration loop.
 host_long_bits = cc.sizeof('void *') * 8
 
+# Detect if ConvertStringToBSTR has been defined in _com_util namespace
+if host_os == 'windows'
+  has_convert_string_to_bstr = cxx.compiles('''
+    #include <comutil.h>
+    int main() {
+        BSTR b = _com_util::ConvertStringToBSTR("test");
+        return b ? 0 : 1;
+    }
+  ''')
+  config_host_data.set('CONFIG_CONVERT_STRING_TO_BSTR', has_convert_string_to_bstr)
+endif
+
 ########################
 # Target configuration #
 ########################
diff --git a/qga/vss-win32/install.cpp b/qga/vss-win32/install.cpp
index 7b25d9098b..5b7a8e9bc5 100644
--- a/qga/vss-win32/install.cpp
+++ b/qga/vss-win32/install.cpp
@@ -549,6 +549,7 @@ STDAPI DllUnregisterServer(void)
 
 
 /* Support function to convert ASCII string into BSTR (used in _bstr_t) */
+#ifndef CONFIG_CONVERT_STRING_TO_BSTR
 namespace _com_util
 {
     BSTR WINAPI ConvertStringToBSTR(const char *ascii) {
@@ -566,6 +567,7 @@ namespace _com_util
         return bstr;
     }
 }
+#endif
 
 /* Stop QGA VSS provider service using Winsvc API  */
 STDAPI StopService(void)
-- 
2.43.0

[PATCH 2/2] util: Move qemu_ftruncate64 from block/file-win32.c to oslib-win32.c

[phind.uet]

From: Nguyen Dinh Phi <phind.uet@gmail.com>

qemu_ftruncate64() is utility function that may be used outside of the block 
layer. Move it to util/oslib-win32.c where other Windows-specific utility 
functions reside.

Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
---
 block/file-win32.c | 32 --------------------------------
 util/oslib-win32.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 32 deletions(-)

diff --git a/block/file-win32.c b/block/file-win32.c
index af9aea631c..8a44853389 100644
--- a/block/file-win32.c
+++ b/block/file-win32.c
@@ -170,38 +170,6 @@ static BlockAIOCB *paio_submit(BlockDriverState *bs, HANDLE hfile,
     return thread_pool_submit_aio(aio_worker, acb, cb, opaque);
 }
 
-int qemu_ftruncate64(int fd, int64_t length)
-{
-    LARGE_INTEGER li;
-    DWORD dw;
-    LONG high;
-    HANDLE h;
-    BOOL res;
-
-    if ((GetVersion() & 0x80000000UL) && (length >> 32) != 0)
-        return -1;
-
-    h = (HANDLE)_get_osfhandle(fd);
-
-    /* get current position, ftruncate do not change position */
-    li.HighPart = 0;
-    li.LowPart = SetFilePointer (h, 0, &li.HighPart, FILE_CURRENT);
-    if (li.LowPart == INVALID_SET_FILE_POINTER && GetLastError() != NO_ERROR) {
-        return -1;
-    }
-
-    high = length >> 32;
-    dw = SetFilePointer(h, (DWORD) length, &high, FILE_BEGIN);
-    if (dw == INVALID_SET_FILE_POINTER && GetLastError() != NO_ERROR) {
-        return -1;
-    }
-    res = SetEndOfFile(h);
-
-    /* back to old position */
-    SetFilePointer(h, li.LowPart, &li.HighPart, FILE_BEGIN);
-    return res ? 0 : -1;
-}
-
 static int set_sparse(int fd)
 {
     DWORD returned;
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index 839b8a4170..766c602172 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -899,3 +899,37 @@ int qemu_shm_alloc(size_t size, Error **errp)
     error_setg(errp, "Shared memory is not supported.");
     return -1;
 }
+
+int qemu_ftruncate64(int fd, int64_t length)
+{
+    LARGE_INTEGER li;
+    DWORD dw;
+    LONG high;
+    HANDLE h;
+    BOOL res;
+
+    if ((GetVersion()&0x80000000UL) && (length >> 32) != 0) {
+        return -1;
+    }
+
+    h = (HANDLE)_get_osfhandle(fd);
+
+    /* get current position, ftruncate do not change position */
+    li.HighPart = 0;
+    li.LowPart = SetFilePointer (h, 0, &li.HighPart, FILE_CURRENT);
+    if (li.LowPart == INVALID_SET_FILE_POINTER && GetLastError() != NO_ERROR) {
+        return -1;
+    }
+
+    high = length >> 32;
+    dw = SetFilePointer(h, (DWORD) length, &high, FILE_BEGIN);
+    if (dw == INVALID_SET_FILE_POINTER && GetLastError() != NO_ERROR) {
+        return -1;
+    }
+    res = SetEndOfFile(h);
+
+    /* back to old position */
+    SetFilePointer(h, li.LowPart, &li.HighPart, FILE_BEGIN);
+    return res ? 0 : -1;
+}
+
-- 
2.43.0

Re: [PATCH 2/2] util: Move qemu_ftruncate64 from block/file-win32.c to oslib-win32.c

[Philippe Mathieu-Daudé]

On 15/12/25 17:45, phind.uet@gmail.com wrote:
> From: Nguyen Dinh Phi <phind.uet@gmail.com>
> 
> qemu_ftruncate64() is utility function that may be used outside of the block
> layer. Move it to util/oslib-win32.c where other Windows-specific utility
> functions reside.
> 
> Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
> ---
>   block/file-win32.c | 32 --------------------------------
>   util/oslib-win32.c | 34 ++++++++++++++++++++++++++++++++++
>   2 files changed, 34 insertions(+), 32 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH 1/2] qga/vss-win32: Fix ConvertStringToBSTR redefinition with newer MinGW

[Marc-André Lureau]

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Hi

On Mon, Dec 15, 2025 at 8:57 PM <phind.uet@gmail.com> wrote:

> From: Nguyen Dinh Phi <phind.uet@gmail.com>
>
> Newer versions of MinGW-w64 provide ConvertStringToBSTR() in the
> _com_util namespace via <comutil.h>. This causes a redefinition
> error when building qemu-ga on Windows with these toolchains.
>
> Add a meson check to detect whether ConvertStringToBSTR is already
> available, and conditionally compile our fallback implementation
> only when the system does not provide one.
>
> Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
> ---
>  meson.build               | 12 ++++++++++++
>  qga/vss-win32/install.cpp |  2 ++
>  2 files changed, 14 insertions(+)
>
> diff --git a/meson.build b/meson.build
> index c5710a6a47..60a980e610 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -3299,6 +3299,18 @@ endif
>  # Detect host pointer size for the target configuration loop.
>  host_long_bits = cc.sizeof('void *') * 8
>
> +# Detect if ConvertStringToBSTR has been defined in _com_util namespace
> +if host_os == 'windows'
> +  has_convert_string_to_bstr = cxx.compiles('''
> +    #include <comutil.h>
> +    int main() {
> +        BSTR b = _com_util::ConvertStringToBSTR("test");
> +        return b ? 0 : 1;
> +    }
> +  ''')
> +  config_host_data.set('CONFIG_CONVERT_STRING_TO_BSTR',
> has_convert_string_to_bstr)
> +endif
> +
>  ########################
>  # Target configuration #
>  ########################
> diff --git a/qga/vss-win32/install.cpp b/qga/vss-win32/install.cpp
> index 7b25d9098b..5b7a8e9bc5 100644
> --- a/qga/vss-win32/install.cpp
> +++ b/qga/vss-win32/install.cpp
> @@ -549,6 +549,7 @@ STDAPI DllUnregisterServer(void)
>
>
>  /* Support function to convert ASCII string into BSTR (used in _bstr_t) */
> +#ifndef CONFIG_CONVERT_STRING_TO_BSTR
>

I wonder if it could check __MINGW64_VERSION_MAJOR >= 14 instead of adding
a configure-time check.

lgtm anyway
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

 namespace _com_util
>  {
>      BSTR WINAPI ConvertStringToBSTR(const char *ascii) {
> @@ -566,6 +567,7 @@ namespace _com_util
>          return bstr;
>      }
>  }
> +#endif
>
>  /* Stop QGA VSS provider service using Winsvc API  */
>  STDAPI StopService(void)
> --
> 2.43.0
>
>

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Re: [PATCH 1/2] qga/vss-win32: Fix ConvertStringToBSTR redefinition with newer MinGW

[Kostiantyn Kostiuk]

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Hi

On Tue, Dec 16, 2025 at 8:26 AM Marc-André Lureau <
marcandre.lureau@redhat.com> wrote:

> Hi
>
> On Mon, Dec 15, 2025 at 8:57 PM <phind.uet@gmail.com> wrote:
>
>> From: Nguyen Dinh Phi <phind.uet@gmail.com>
>>
>> Newer versions of MinGW-w64 provide ConvertStringToBSTR() in the
>> _com_util namespace via <comutil.h>. This causes a redefinition
>> error when building qemu-ga on Windows with these toolchains.
>>
>> Add a meson check to detect whether ConvertStringToBSTR is already
>> available, and conditionally compile our fallback implementation
>> only when the system does not provide one.
>>
>> Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
>> ---
>>  meson.build               | 12 ++++++++++++
>>  qga/vss-win32/install.cpp |  2 ++
>>  2 files changed, 14 insertions(+)
>>
>> diff --git a/meson.build b/meson.build
>> index c5710a6a47..60a980e610 100644
>> --- a/meson.build
>> +++ b/meson.build
>> @@ -3299,6 +3299,18 @@ endif
>>  # Detect host pointer size for the target configuration loop.
>>  host_long_bits = cc.sizeof('void *') * 8
>>
>> +# Detect if ConvertStringToBSTR has been defined in _com_util namespace
>> +if host_os == 'windows'
>> +  has_convert_string_to_bstr = cxx.compiles('''
>> +    #include <comutil.h>
>> +    int main() {
>> +        BSTR b = _com_util::ConvertStringToBSTR("test");
>> +        return b ? 0 : 1;
>> +    }
>> +  ''')
>> +  config_host_data.set('CONFIG_CONVERT_STRING_TO_BSTR',
>> has_convert_string_to_bstr)
>> +endif
>> +
>>  ########################
>>  # Target configuration #
>>  ########################
>> diff --git a/qga/vss-win32/install.cpp b/qga/vss-win32/install.cpp
>> index 7b25d9098b..5b7a8e9bc5 100644
>> --- a/qga/vss-win32/install.cpp
>> +++ b/qga/vss-win32/install.cpp
>> @@ -549,6 +549,7 @@ STDAPI DllUnregisterServer(void)
>>
>>
>>  /* Support function to convert ASCII string into BSTR (used in _bstr_t)
>> */
>> +#ifndef CONFIG_CONVERT_STRING_TO_BSTR
>>
>
> I wonder if it could check __MINGW64_VERSION_MAJOR >= 14 instead of adding
> a configure-time check.
>

@Peter Maydell <peter.maydell@linaro.org> preferred to avoid specific
version-number checks.
See: https://gitlab.com/qemu-project/qemu/-/issues/3217#note_2935451782

I also preferred the idea of checking the real function present instead of
the version of the component.

Reviewed-by: Kostiantyn Kostiuk <kkostiuk@redhat.com>


>
> lgtm anyway
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>
>  namespace _com_util
>>  {
>>      BSTR WINAPI ConvertStringToBSTR(const char *ascii) {
>> @@ -566,6 +567,7 @@ namespace _com_util
>>          return bstr;
>>      }
>>  }
>> +#endif
>>
>>  /* Stop QGA VSS provider service using Winsvc API  */
>>  STDAPI StopService(void)
>> --
>> 2.43.0
>>
>>

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Re: [PATCH 1/2] qga/vss-win32: Fix ConvertStringToBSTR redefinition with newer MinGW

[Pierrick Bouvier]

On 12/15/25 8:45 AM, phind.uet@gmail.com wrote:
> From: Nguyen Dinh Phi <phind.uet@gmail.com>
> 
> Newer versions of MinGW-w64 provide ConvertStringToBSTR() in the
> _com_util namespace via <comutil.h>. This causes a redefinition
> error when building qemu-ga on Windows with these toolchains.
> 
> Add a meson check to detect whether ConvertStringToBSTR is already
> available, and conditionally compile our fallback implementation
> only when the system does not provide one.
> 
> Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
> ---
>   meson.build               | 12 ++++++++++++
>   qga/vss-win32/install.cpp |  2 ++
>   2 files changed, 14 insertions(+)

Thanks for the fix, I was looking at this error.
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>

Re: [PATCH 2/2] util: Move qemu_ftruncate64 from block/file-win32.c to oslib-win32.c

[Pierrick Bouvier]

On 12/15/25 8:45 AM, phind.uet@gmail.com wrote:
> From: Nguyen Dinh Phi <phind.uet@gmail.com>
> 
> qemu_ftruncate64() is utility function that may be used outside of the block
> layer. Move it to util/oslib-win32.c where other Windows-specific utility
> functions reside.
> 
> Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
> ---
>   block/file-win32.c | 32 --------------------------------
>   util/oslib-win32.c | 34 ++++++++++++++++++++++++++++++++++
>   2 files changed, 34 insertions(+), 32 deletions(-)
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>

Re: [PATCH 1/2] qga/vss-win32: Fix ConvertStringToBSTR redefinition with newer MinGW

[Pierrick Bouvier]

On 12/16/25 1:53 AM, Kostiantyn Kostiuk wrote:
> Hi
> 
> On Tue, Dec 16, 2025 at 8:26 AM Marc-André Lureau 
> <marcandre.lureau@redhat.com <mailto:marcandre.lureau@redhat.com>> wrote:
> 
>     Hi
> 
>     On Mon, Dec 15, 2025 at 8:57 PM <phind.uet@gmail.com
>     <mailto:phind.uet@gmail.com>> wrote:
> 
>         From: Nguyen Dinh Phi <phind.uet@gmail.com
>         <mailto:phind.uet@gmail.com>>
> 
>         Newer versions of MinGW-w64 provide ConvertStringToBSTR() in the
>         _com_util namespace via <comutil.h>. This causes a redefinition
>         error when building qemu-ga on Windows with these toolchains.
> 
>         Add a meson check to detect whether ConvertStringToBSTR is already
>         available, and conditionally compile our fallback implementation
>         only when the system does not provide one.
> 
>         Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com
>         <mailto:phind.uet@gmail.com>>
>         ---
>           meson.build               | 12 ++++++++++++
>           qga/vss-win32/install.cpp |  2 ++
>           2 files changed, 14 insertions(+)
> 
>         diff --git a/meson.build b/meson.build
>         index c5710a6a47..60a980e610 100644
>         --- a/meson.build
>         +++ b/meson.build
>         @@ -3299,6 +3299,18 @@ endif
>           # Detect host pointer size for the target configuration loop.
>           host_long_bits = cc.sizeof('void *') * 8
> 
>         +# Detect if ConvertStringToBSTR has been defined in _com_util
>         namespace
>         +if host_os == 'windows'
>         +  has_convert_string_to_bstr = cxx.compiles('''
>         +    #include <comutil.h>
>         +    int main() {
>         +        BSTR b = _com_util::ConvertStringToBSTR("test");
>         +        return b ? 0 : 1;
>         +    }
>         +  ''')
>         +  config_host_data.set('CONFIG_CONVERT_STRING_TO_BSTR',
>         has_convert_string_to_bstr)
>         +endif
>         +
>           ########################
>           # Target configuration #
>           ########################
>         diff --git a/qga/vss-win32/install.cpp b/qga/vss-win32/install.cpp
>         index 7b25d9098b..5b7a8e9bc5 100644
>         --- a/qga/vss-win32/install.cpp
>         +++ b/qga/vss-win32/install.cpp
>         @@ -549,6 +549,7 @@ STDAPI DllUnregisterServer(void)
> 
> 
>           /* Support function to convert ASCII string into BSTR (used in
>         _bstr_t) */
>         +#ifndef CONFIG_CONVERT_STRING_TO_BSTR
> 
> 
>     I wonder if it could check __MINGW64_VERSION_MAJOR >= 14 instead of
>     adding a configure-time check.
> 
> 
> @Peter Maydell <mailto:peter.maydell@linaro.org> preferred to avoid 
> specific version-number checks.
> See: https://gitlab.com/qemu-project/qemu/-/issues/3217#note_2935451782 
> <https://gitlab.com/qemu-project/qemu/-/issues/3217#note_2935451782>
> 
> I also preferred the idea of checking the real function present instead 
> of the version of the component.
> 
> Reviewed-by: Kostiantyn Kostiuk <kkostiuk@redhat.com 
> <mailto:kkostiuk@redhat.com>>
> 
> 
>     lgtm anyway
>     Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com
>     <mailto:marcandre.lureau@redhat.com>>
> 
>           namespace _com_util
>           {
>               BSTR WINAPI ConvertStringToBSTR(const char *ascii) {
>         @@ -566,6 +567,7 @@ namespace _com_util
>                   return bstr;
>               }
>           }
>         +#endif
> 
>           /* Stop QGA VSS provider service using Winsvc API  */
>           STDAPI StopService(void)
>         -- 
>         2.43.0
> 

When cross-compiling using fedora-win64-cross, it can find the function 
in header but does not link it.

$ podman run --pull newer --init --rm -it -v $(pwd):$(pwd) -w $(pwd) \
docker.io/pbolinaro/qemu-ci:fedora-win64-cross \
bash -cx './configure $QEMU_CONFIGURE_OPTS && ninja -C build install'
...
[4434/4696] Linking target qga/vss-win32/qga-vss.dll
FAILED: qga/vss-win32/qga-vss.dll
x86_64-w64-mingw32-g++ -m64  -o qga/vss-win32/qga-vss.dll 
qga/vss-win32/qga-vss.dll.p/requester.cpp.obj 
qga/vss-win32/qga-vss.dll.p/provider.cpp.obj 
qga/vss-win32/qga-vss.dll.p/install.cpp.obj 
qga/vss-win32/qga-vss.dll.p/vss-debug.cpp.obj 
-Wl,--allow-shlib-undefined -shared ../qga/vss-win32/qga-vss.def 
-Wl,--start-group -Wl,--out-implib=qga/vss-win32/qga-vss.dll.a 
-fstack-protector-strong -Wl,--no-seh -Wl,--nxcompat -Wl,--dynamicbase 
-Wl,--high-entropy-va -fstack-protector-all -fstack-protector-strong 
-Wl,--add-stdcall-alias -Wl,--enable-stdcall-fixup -lws2_32 -lole32 
-loleaut32 -lshlwapi -luuid -lkernel32 -luser32 -lgdi32 -lwinspool 
-lshell32 -lcomdlg32 -ladvapi32 -Wl,--end-group
/usr/lib/gcc/x86_64-w64-mingw32/14.2.1/../../../../x86_64-w64-mingw32/bin/ld: 
qga/vss-win32/qga-vss.dll.p/install.cpp.obj: in function 
`_bstr_t::Data_t::Data_t(char const*)':
/usr/x86_64-w64-mingw32/sys-root/mingw/include/comutil.h:279:(.text+0x1dc8): 
undefined reference to `_com_util::ConvertStringToBSTR(char const*)'
...

Looking into mingw files, the symbol is not there.
$ nm /usr/x86_64-w64-mingw32/sys-root/mingw/lib/lib*.a |
grep -i ConvertStringToBSTR

It's present in header file though:
/usr/x86_64-w64-mingw32/sys-root/mingw/include/comutil.h

Not sure if something is missing in mingw, or if it's missing an 
attribute to say it should be available at runtime only, but in all 
cases, a simple fix to the patch is:

diff --git a/meson.build b/meson.build
index ab19317f5af..113296544c4 100644
--- a/meson.build
+++ b/meson.build
@@ -3261,7 +3261,7 @@ host_long_bits = cc.sizeof('void *') * 8

  # Detect if ConvertStringToBSTR has been defined in _com_util namespace
  if host_os == 'windows'
-  has_convert_string_to_bstr = cxx.compiles('''
+  has_convert_string_to_bstr = cxx.links('''
      #include <comutil.h>
      int main() {
          BSTR b = _com_util::ConvertStringToBSTR("test");

I would recommend to use cxx.links instead of cxx.compiles for now.

Regards,
Pierrick