chardev/baum: Fix compiler warning for Windows builds

[PATCH trivial] chardev/baum: Fix compiler warning for Windows builds

Posted by Stefan Weil via 3 months, 1 week ago

Compiler warning:

../chardev/baum.c:657:25: warning: comparison between pointer and integer

Use brlapi_fileDescriptor instead of int for brlapi_fd and
BRLAPI_INVALID_FILE_DESCRIPTOR instead of -1.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
---

This is a rather old patch which I now use since more than two years
to support Braille with QEMU on Windows.

It's a hack (because Windows uses a pointer (64 bit) which is
assigned to an int (32 bit), but it seems to work.

Regards,
Stefan


 chardev/baum.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/chardev/baum.c b/chardev/baum.c
index f3e8cd27f0..5c3587dda5 100644
--- a/chardev/baum.c
+++ b/chardev/baum.c
@@ -94,7 +94,7 @@ struct BaumChardev {
     Chardev parent;
 
     brlapi_handle_t *brlapi;
-    int brlapi_fd;
+    brlapi_fileDescriptor brlapi_fd;
     unsigned int x, y;
     bool deferred_init;
 
@@ -654,7 +654,7 @@ static void baum_chr_open(Chardev *chr,
     baum->brlapi = handle;
 
     baum->brlapi_fd = brlapi__openConnection(handle, NULL, NULL);
-    if (baum->brlapi_fd == -1) {
+    if (baum->brlapi_fd == BRLAPI_INVALID_FILE_DESCRIPTOR) {
         error_setg(errp, "brlapi__openConnection: %s",
                    brlapi_strerror(brlapi_error_location()));
         g_free(handle);
-- 
2.47.2

Re: [PATCH trivial] chardev/baum: Fix compiler warning for Windows builds

Posted by Michael Tokarev 3 months ago

On 09.08.2025 09:13, Stefan Weil via wrote:
> Compiler warning:
> 
> ../chardev/baum.c:657:25: warning: comparison between pointer and integer
> 
> Use brlapi_fileDescriptor instead of int for brlapi_fd and
> BRLAPI_INVALID_FILE_DESCRIPTOR instead of -1.
> 
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> ---
> 
> This is a rather old patch which I now use since more than two years
> to support Braille with QEMU on Windows.
> 
> It's a hack (because Windows uses a pointer (64 bit) which is
> assigned to an int (32 bit), but it seems to work.

Queued to the trivial-patches tree, with the following addition:

diff --git a/chardev/baum.c b/chardev/baum.c
index 5c3587dda5..ad68321504 100644
--- a/chardev/baum.c
+++ b/chardev/baum.c
@@ -665,6 +665,10 @@ static void baum_chr_open(Chardev *chr,

      baum->cellCount_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, 
baum_cellCount_timer_cb, baum);

+    /*
+     * On Windows, brlapi_fd is a pointer, which is being used here
+     * as an integer, but in practice it seems to work
+     */
      qemu_set_fd_handler(baum->brlapi_fd, baum_chr_read, NULL, baum);
  }

Thanks,

/mjt

Re: [PATCH trivial] chardev/baum: Fix compiler warning for Windows builds

Posted by Samuel Thibault 3 months ago

Stefan Weil, le sam. 09 août 2025 08:13:02 +0200, a ecrit:
> Compiler warning:
> 
> ../chardev/baum.c:657:25: warning: comparison between pointer and integer
> 
> Use brlapi_fileDescriptor instead of int for brlapi_fd and
> BRLAPI_INVALID_FILE_DESCRIPTOR instead of -1.
> 
> Signed-off-by: Stefan Weil <sw@weilnetz.de>

Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

Thanks!

> ---
> 
> This is a rather old patch which I now use since more than two years
> to support Braille with QEMU on Windows.

Just curious: what do you use this Braille support for?

Samuel

> It's a hack (because Windows uses a pointer (64 bit) which is
> assigned to an int (32 bit), but it seems to work.
> 
> Regards,
> Stefan
> 
> 
>  chardev/baum.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/chardev/baum.c b/chardev/baum.c
> index f3e8cd27f0..5c3587dda5 100644
> --- a/chardev/baum.c
> +++ b/chardev/baum.c
> @@ -94,7 +94,7 @@ struct BaumChardev {
>      Chardev parent;
>  
>      brlapi_handle_t *brlapi;
> -    int brlapi_fd;
> +    brlapi_fileDescriptor brlapi_fd;
>      unsigned int x, y;
>      bool deferred_init;
>  
> @@ -654,7 +654,7 @@ static void baum_chr_open(Chardev *chr,
>      baum->brlapi = handle;
>  
>      baum->brlapi_fd = brlapi__openConnection(handle, NULL, NULL);
> -    if (baum->brlapi_fd == -1) {
> +    if (baum->brlapi_fd == BRLAPI_INVALID_FILE_DESCRIPTOR) {
>          error_setg(errp, "brlapi__openConnection: %s",
>                     brlapi_strerror(brlapi_error_location()));
>          g_free(handle);
> -- 
> 2.47.2
> 

-- 
Samuel
/*
 * Oops. The kernel tried to access some bad page. We'll have to
 * terminate things with extreme prejudice.
*/
die_if_kernel("Oops", regs, error_code);
(From linux/arch/i386/mm/fault.c)

Re: [PATCH trivial] chardev/baum: Fix compiler warning for Windows builds

Posted by Markus Armbruster 3 months, 1 week ago

Stefan Weil via <qemu-devel@nongnu.org> writes:

> Compiler warning:
>
> ../chardev/baum.c:657:25: warning: comparison between pointer and integer
>
> Use brlapi_fileDescriptor instead of int for brlapi_fd and
> BRLAPI_INVALID_FILE_DESCRIPTOR instead of -1.
>
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> ---
>
> This is a rather old patch which I now use since more than two years
> to support Braille with QEMU on Windows.
>
> It's a hack (because Windows uses a pointer (64 bit) which is
> assigned to an int (32 bit), but it seems to work.

Would a code comment pointing out the hack be useful?

> Regards,
> Stefan
>
>
>  chardev/baum.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/chardev/baum.c b/chardev/baum.c
> index f3e8cd27f0..5c3587dda5 100644
> --- a/chardev/baum.c
> +++ b/chardev/baum.c
> @@ -94,7 +94,7 @@ struct BaumChardev {
>      Chardev parent;
>  
>      brlapi_handle_t *brlapi;
> -    int brlapi_fd;
> +    brlapi_fileDescriptor brlapi_fd;
>      unsigned int x, y;
>      bool deferred_init;
>  
> @@ -654,7 +654,7 @@ static void baum_chr_open(Chardev *chr,
>      baum->brlapi = handle;
>  
>      baum->brlapi_fd = brlapi__openConnection(handle, NULL, NULL);
> -    if (baum->brlapi_fd == -1) {
> +    if (baum->brlapi_fd == BRLAPI_INVALID_FILE_DESCRIPTOR) {
>          error_setg(errp, "brlapi__openConnection: %s",
>                     brlapi_strerror(brlapi_error_location()));
>          g_free(handle);

Re: [PATCH trivial] chardev/baum: Fix compiler warning for Windows builds

Posted by Stefan Weil via 3 months, 1 week ago

Am 09.08.25 um 08:20 schrieb Markus Armbruster:

> Stefan Weil via <qemu-devel@nongnu.org> writes:
>
>> Compiler warning:
>>
>> ../chardev/baum.c:657:25: warning: comparison between pointer and integer
>>
>> Use brlapi_fileDescriptor instead of int for brlapi_fd and
>> BRLAPI_INVALID_FILE_DESCRIPTOR instead of -1.
>>
>> Signed-off-by: Stefan Weil <sw@weilnetz.de>
>> ---
>>
>> This is a rather old patch which I now use since more than two years
>> to support Braille with QEMU on Windows.
>>
>> It's a hack (because Windows uses a pointer (64 bit) which is
>> assigned to an int (32 bit), but it seems to work.
> Would a code comment pointing out the hack be useful?


Maybe. Michael, feel free to add such a comment if you take the patch.

Note that there is also a compiler warning for 
`qemu_set_fd_handler(baum->brlapi_fd, baum_chr_read, NULL, baum)`:

warning: passing argument 1 of ‘qemu_set_fd_handler’ makes integer from 
pointer without a cast [-Wint-conversion]

That would be a good place for the comment.

Stefan