Re: [Qemu-devel] Hacks for building on gcc 7 / Fedora 26

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Daniel P. Berrange (berrange@redhat.com) wrote:
> On Fri, Apr 07, 2017 at 03:38:47PM +0100, Dr. David Alan Gilbert wrote:
> > Hi,
> >    Fedora 26 has gcc 7.0.1 which has the normal compliment
> > of new fussy warnings; so far I've posted :
> > 
> > tests/check-qdict: Fix missing brackets
> > slirp/smb: Replace constant strings by glib string
> > 
> > that fix one actual mistake and work around something it's being
> > fussy over.
> > 
> > But I've also got a pile of hacks, attached below that I'm
> > not too sure what I'll do with them yet, but they're attached
> > for anyone else trying to build.  Note they're smoke-only-tested.
> > 
> > I also have gcc bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80346
> > filed for what I reckon is a couple of overly pessimistic warnings.
> 
> 
> > diff --git a/include/qemu/iov.h b/include/qemu/iov.h
> > index bd9fd55b0a..ebb0221140 100644
> > --- a/include/qemu/iov.h
> > +++ b/include/qemu/iov.h
> > @@ -46,7 +46,7 @@ static inline size_t
> >  iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
> >               size_t offset, const void *buf, size_t bytes)
> >  {
> > -    if (__builtin_constant_p(bytes) && iov_cnt &&
> > +    if (__builtin_constant_p(bytes) && iov_cnt && bytes <= INT_MAX &&
> >          offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
> >          memcpy(iov[0].iov_base + offset, buf, bytes);
> >          return bytes;
> > @@ -59,7 +59,7 @@ static inline size_t
> >  iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
> >             size_t offset, void *buf, size_t bytes)
> >  {
> > -    if (__builtin_constant_p(bytes) && iov_cnt &&
> > +    if (__builtin_constant_p(bytes) && iov_cnt && bytes <= INT_MAX &&
> >          offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
> >          memcpy(buf, iov[0].iov_base + offset, bytes);
> >          return bytes;

tbh I don't know what the right fix for this is;  the gcc discussion
confused me as to why it thinks it can be a valid case.

> > diff --git a/tests/bios-tables-test.c b/tests/bios-tables-test.c
> > index 88dbf97853..c55de4f65b 100644
> > --- a/tests/bios-tables-test.c
> > +++ b/tests/bios-tables-test.c
> > @@ -98,7 +98,7 @@ static void test_acpi_rsdt_table(test_data *data)
> >      AcpiRsdtDescriptorRev1 *rsdt_table = &data->rsdt_table;
> >      uint32_t addr = data->rsdp_table.rsdt_physical_address;
> >      uint32_t *tables;
> > -    int tables_nr;
> > +    unsigned int tables_nr;
> >      uint8_t checksum;
> >  
> >      /* read the header */

> Unless I've missed a patch somwhere, I think the problems that these two
> chunks are fixing are still needed for current git master, to stop warnings
> in the unit tests.
> 

The second one of those I can post a patch for; the trick is to change
the g_assert_cmpint to a g_assert and then gcc realises the bad case
can't happen.  I'll post that in a few mins.

Dave
> 
> Regards,
> Daniel
> -- 
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--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK