[Fix] Avoid recent gcc error messages about unused write(2) return value

 
See attachment.

[Fix] Avoid recent gcc error messages about unused write(2) return value

--
Damien Cassou
http://damiencassou.seasidehosting.st

 
2009/1/30 Damien Cassou <[hidden email]>:
>
> See attachment.
>
> [Fix] Avoid recent gcc error messages about unused write(2) return value

There is a reason why GCC forces you to check the return value.

Cheers
Philippe

 
On Fri, Jan 30, 2009 at 2:22 PM, Philippe Marschall
<[hidden email]> wrote:
> There is a reason why GCC forces you to check the return value.

This was already ignored before, just with the wrong trick. I don't
know enough about VMs to decide what can be ignored or not :-).

--
Damien Cassou
http://damiencassou.seasidehosting.st

 

On 30.01.2009, at 14:22, Philippe Marschall wrote:

>
> 2009/1/30 Damien Cassou <[hidden email]>:
>>
>> See attachment.
>>
>> [Fix] Avoid recent gcc error messages about unused write(2) return  
>> value
>
> There is a reason why GCC forces you to check the return value.


This is actually not GCC's fault, but newer header files declare  
write() with the warn_unused_result attribute to enforce that check.

- Bert -

 
Damien Cassou wrote:
>
> [Fix] Avoid recent gcc error messages about unused write(2) return value
>
>  

I'm not seeing an error, or even a warning from gcc 4.3.2 for this, on
the latest svn/trunk.    Could you post the error your getting, and what
options you are giving to gcc?

                                                         -gavin...

 
On Fri, Jan 30, 2009 at 6:44 PM, Gavin Romig-Koch <[hidden email]> wrote:
> I'm not seeing an error, or even a warning from gcc 4.3.2 for this, on the
> latest svn/trunk.    Could you post the error your getting, and what options
> you are giving to gcc?

I do not pass any option to gcc.

$ gcc --version
gcc (Ubuntu 4.3.2-1ubuntu12) 4.3.2

The script I use to compile the vm:

$ cd /tmp && svn co http://squeakvm.org/svn/squeak/trunk squeak-svn &&
cd squeak-svn && mkdir bld && cd bld &&
../platforms/unix/config/configure --prefix=/opt/squeak && make &&
sudo make install

cc1: warnings being treated as errors
In file included from
/tmp/squeak-svn/platforms/unix/vm-display-fbdev/sqUnixFBDevMouse.c:109,
                 from
/tmp/squeak-svn/platforms/unix/vm-display-fbdev/sqUnixFBDev.c:128:
/tmp/squeak-svn/platforms/unix/vm-display-fbdev/sqUnixFBDevMousePS2.c:
In function 'ms_ps2_send':
/tmp/squeak-svn/platforms/unix/vm-display-fbdev/sqUnixFBDevMousePS2.c:113:
error: ignoring return value of 'write', declared with attribute
warn_unused_result
/tmp/squeak-svn/platforms/unix/vm-display-fbdev/sqUnixFBDevMousePS2.c:
In function 'ms_ps2_disable':
/tmp/squeak-svn/platforms/unix/vm-display-fbdev/sqUnixFBDevMousePS2.c:144:
error: ignoring return value of 'write', declared with attribute
warn_unused_result
make[1]: *** [sqUnixFBDev.lo] Error 1
make: *** [vm-display-fbdev.la] Error 2

--
Damien Cassou
http://damiencassou.seasidehosting.st

 
Damien Cassou wrote:
>
> [Fix] Avoid recent gcc error messages about unused write(2) return value
>
>  
What a mess: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25509

with the additional fact that the makefile in vm-display-fbdev turns on
-Werror.

In any case, if this code has to be changed, I think it would be better
in this case to check the return values than to go to extra ordinary
lengths to ignore them.    Patch attached.

                                                                                                 
-gavin...


Index: platforms/unix/vm-display-fbdev/sqUnixFBDevMousePS2.c
===================================================================
--- platforms/unix/vm-display-fbdev/sqUnixFBDevMousePS2.c (revision 1966)
+++ platforms/unix/vm-display-fbdev/sqUnixFBDevMousePS2.c (working copy)
@@ -110,11 +110,15 @@
   for (i= 0;  i < len;  ++i)
     {
     resend:
-      (void)write(self->fd, command + i, 1);
+      if (1 != write(self->fd, command + i, 1))
+ {
+  dprintf("%s: send failed during write\n", self->msName);
+  return 0;
+ }
       dprintf(">%02x\n", command[i]);
       if (1 != ms_read(self, buf, 1, 1, PS2_SEND_DELAY))
  {
-  dprintf("%s: send failed\n", self->msName);
+  dprintf("%s: send failed during read\n", self->msName);
   return 0;
  }
       switch (buf[0])
@@ -141,7 +145,11 @@
 {
   unsigned char command[]= { PS2_DISABLE };
   dprintf("%s: disable\n", self->msName);
-  (void)write(self->fd, command, 1);
+  if (1 != write(self->fd, command, 1))
+    {
+      dprintf("%s: disable failed during write\n", self->msName);
+      return;
+    }
   dprintf(">%02x\n", command[0]);
   while (1 == ms_read(self, command, 1, 1, PS2_DISABLE_DELAY))
     if (PS2_OK == command[0])