Re: [Qemu-devel] [PATCH v2 0/3] Fix strncpy() warnings for GCC8 new -Wstringop-truncation

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Dec 18, 2018 at 09:31:00AM -0500, Michael S. Tsirkin wrote:
> On Tue, Dec 18, 2018 at 12:03:30PM +0100, Philippe Mathieu-Daudé wrote:
> > GCC 8 new warning prevents builds to success since quite some time.
> > First report on the mailing list is in July 2018:
> > https://lists.gnu.org/archive/html/qemu-devel/2018-07/msg03723.html
> > 
> > Various intents has been sent to fix this:
> > - Incorrectly using g_strlcpy()
> >   https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg03705.html
> >   https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg03706.html
> > - Using assert() and strpadcpy()
> >   https://lists.gnu.org/archive/html/qemu-devel/2018-11/msg03938.html
> > - Use #pragma GCC diagnostic ignored "-Wstringop-truncation"
> >   https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg04261.html
> > - adding an inline wrapper with said pragma in there
> >   https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg04261.html
> > - -Wno-stringop-truncation is the makefile
> >   https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg04261.html
> > 
> > This series replace the strncpy() calls by strpadcpy() which seemed
> > to me the saniest option.
> > 
> > Regards,
> > 
> > Phil.
> 
> Do you happen to know why does it build fine with
> Gcc 8.2.1?
> 
> Reading the GCC manual it seems that
> there is a "nostring" attribute

Sorry that should be "nonstring".


> that means
> "might not be 0 terminated".
> I think we should switch to that which fixes the warning
> but also warns if someone tries to misuse these
> as C-strings.
> 
> Seems to be a better option, does it not?
> 

Also maybe we can make strpadcpy check for the nonstring
attribute too somehow?
Or did gcc just hardcode the strncpy name?

> > Marc-André Lureau (1):
> >   hw/acpi: Replace strncpy() by strpadcpy(pad='\0')
> > 
> > Philippe Mathieu-Daudé (2):
> >   block/sheepdog: Replace strncpy() by strpadcpy(pad='\0')
> >   migration: Replace strncpy() by strpadcpy(pad='\0')
> > 
> >  block/sheepdog.c         |  6 +++---
> >  hw/acpi/aml-build.c      |  6 ++++--
> >  hw/acpi/core.c           | 13 +++++++------
> >  migration/global_state.c |  4 ++--
> >  4 files changed, 16 insertions(+), 13 deletions(-)
> > 
> > -- 
> > 2.17.2