ppc: e500: use g_strdup_printf() instead of snprintf()

ppc: e500: use g_strdup_printf() instead of snprintf()

qemu-system-ppc fails to build with GCC 8.0.1:

/home/hsp/src/qemu-master/hw/ppc/e500.c: In function ‘ppce500_load_device_tree’:
/home/hsp/src/qemu-master/hw/ppc/e500.c:442:37: error: ‘/pic@’
directive output may be truncated writing 5 bytes into a region of
size between 1 and 128 [-Werror=format-truncation=]
     snprintf(mpic, sizeof(mpic), "%s/pic@%llx", soc, MPC8544_MPIC_REGS_OFFSET);
                                     ^~~~~
In file included from /usr/include/stdio.h:862,
                 from /home/hsp/src/qemu-master/include/qemu/osdep.h:68,
                 from /home/hsp/src/qemu-master/hw/ppc/e500.c:17:
/usr/include/bits/stdio2.h:64:10: note: ‘__builtin___snprintf_chk’
output between 11 and 138 bytes into a destination of size 128
   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        __bos (__s), __fmt, __va_arg_pack ());
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/hsp/src/qemu-master/hw/ppc/e500.c:470:39: error:
‘/global-utilities@’ directive output may be truncated writing 18
bytes into a region of size between 1 and 128
[-Werror=format-truncation=]
     snprintf(gutil, sizeof(gutil), "%s/global-utilities@%llx", soc,
                                       ^~~~~~~~~~~~~~~~~~
In file included from /usr/include/stdio.h:862,
                 from /home/hsp/src/qemu-master/include/qemu/osdep.h:68,
                 from /home/hsp/src/qemu-master/hw/ppc/e500.c:17:
/usr/include/bits/stdio2.h:64:10: note: ‘__builtin___snprintf_chk’
output between 24 and 151 bytes into a destination of size 128
   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        __bos (__s), __fmt, __va_arg_pack ());
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/hsp/src/qemu-master/hw/ppc/e500.c:477:36: error: ‘/msi@’
directive output may be truncated writing 5 bytes into a region of
size between 0 and 127 [-Werror=format-truncation=]
     snprintf(msi, sizeof(msi), "/%s/msi@%llx", soc, MPC8544_MSI_REGS_OFFSET);
                                    ^~~~~
In file included from /usr/include/stdio.h:862,
                 from /home/hsp/src/qemu-master/include/qemu/osdep.h:68,
                 from /home/hsp/src/qemu-master/hw/ppc/e500.c:17:
/usr/include/bits/stdio2.h:64:10: note: ‘__builtin___snprintf_chk’
output between 12 and 139 bytes into a destination of size 128
   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        __bos (__s), __fmt, __va_arg_pack ());
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by converting e500 to use g_strdup_printf()+g_free() instead
of snprintf(). This is done globally, even for call sites that don't
break build, since this is the preferred practice in QEMU.

Reported-by: Howard Spoelstra <hsp.cat7@gmail.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 152568372989.443627.900708381919207053.stgit@bahia.lan
Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>