Re: compile warning in i8259.c

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 3/15/21 4:44 PM, Christian Borntraeger wrote:
> On 15.03.21 16:14, Christian Borntraeger wrote:
>> For some time now I do see the following, when I compile x86-softmmu
>> on s390:
>>
>> FAILED: libcommon.fa.p/hw_intc_i8259.c.o
>> cc -Ilibcommon.fa.p -I. -I.. -Iqapi -Itrace -Iui -Iui/shader
>> -I/usr/include/capstone -I/usr/include/glib-2.0
>> -I/usr/lib64/glib-2.0/include -I/usr/include/libmount
>> -I/usr/include/blkid -I/usr/include/gio-unix-2.0
>> -I/usr/include/libusb-1.0 -I/usr/include/vte-2.91
>> -I/usr/include/pango-1.0 -I/usr/include/harfbuzz
>> -I/usr/include/freetype2 -I/usr/include/libpng16
>> -I/usr/include/fribidi -I/usr/include/libxml2 -I/usr/include/cairo
>> -I/usr/include/pixman-1 -I/usr/include/gtk-3.0
>> -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/atk-1.0
>> -I/usr/include/at-spi2-atk/2.0 -I/usr/include/dbus-1.0
>> -I/usr/lib64/dbus-1.0/include -I/usr/include/at-spi-2.0
>> -I/usr/include/virgl -I/usr/include/p11-kit-1 -I/usr/include/SDL2
>> -I/usr/include/cacard -I/usr/include/nss3 -I/usr/include/nspr4
>> -I/usr/include/slirp -fdiagnostics-color=auto -pipe -Wall
>> -Winvalid-pch -Werror -std=gnu99 -O2 -g -isystem
>> /home/cborntra/REPOS/qemu/linux-headers -isystem linux-headers -iquote
>> . -iquote /home/cborntra/REPOS/qemu -iquote
>> /home/cborntra/REPOS/qemu/include -iquote
>> /home/cborntra/REPOS/qemu/disas/libvixl -iquote
>> /home/cborntra/REPOS/qemu/tcg/s390 -iquote
>> /home/cborntra/REPOS/qemu/accel/tcg -pthread -U_FORTIFY_SOURCE
>> -D_FORTIFY_SOURCE=2 -m64 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64
>> -D_LARGEFILE_SOURCE -Wstrict-prototypes -Wredundant-decls -Wundef
>> -Wwrite-strings -Wmissing-prototypes -fno-strict-aliasing -fno-common
>> -fwrapv -Wold-style-declaration -Wold-style-definition -Wtype-limits
>> -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers
>> -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined
>> -Wimplicit-fallthrough=2 -Wno-missing-include-dirs
>> -Wno-shift-negative-value -Wno-psabi -fstack-protector-strong -fPIC
>> -DSTRUCT_IOVEC_DEFINED -D_REENTRANT -Wno-undef -D_DEFAULT_SOURCE
>> -D_XOPEN_SOURCE=600 -DNCURSES_WIDECHAR -MD -MQ
>> libcommon.fa.p/hw_intc_i8259.c.o -MF
>> libcommon.fa.p/hw_intc_i8259.c.o.d -o libcommon.fa.p/hw_intc_i8259.c.o
>> -c ../hw/intc/i8259.c
>> ../hw/intc/i8259.c: In function ‘pic_read_irq’:
>> ../hw/intc/i8259.c:203:13: error: ‘irq2’ may be used uninitialized in
>> this function [-Werror=maybe-uninitialized]
>>    203 |         irq = irq2 + 8;
>>        |         ~~~~^~~~~~~~~~
>> cc1: all warnings being treated as errors
>>
>>
>> Due to other compile warnings I find this hard to bisect. Has anyone
>> seen this as well?
> 
> cc Michael, Paolo,
> 
> Something like
> 
> diff --git a/hw/intc/i8259.c b/hw/intc/i8259.c
> index 344fd04db14d..7335b7a06a67 100644
> --- a/hw/intc/i8259.c
> +++ b/hw/intc/i8259.c
> @@ -176,7 +176,7 @@ static void pic_intack(PICCommonState *s, int irq)
>  int pic_read_irq(DeviceState *d)
>  {
>      PICCommonState *s = PIC_COMMON(d);
> -    int irq, irq2, intno;
> +    int irq, irq2 = 0, intno;
>  
>      irq = pic_get_irq(s);
>      if (irq >= 0) {
> 
> 
> would do the trick. Let me know if I should do a proper patch or if you
> want to have things solved differently.

Since you ask, I'd love to have things solved differently...
One PIC has 8 IRQs, so we should model 2 cascaded PICs as 2 cascaded
QOM PICs. But this code is so old and heavily used that my desire
is unlikely to be realized. And your patch is simpler :>