On 4/30/19 3:09 PM, Alistair Francis wrote: > Fix this warning when building with GCC9 on Fedora 30: > In function ‘strncpy’, > inlined from ‘sys_uname’ at /home/alistair/qemu/linux-user/uname.c:94:3: > /usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ > output may be truncated copying 64 bytes from a string of length 64 > [-Werror=stringop-truncation] > 106 | return __builtin___strncpy_chk (__dest, __src, __len, __bos > (__dest)); > | > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Signed-off-by: Alistair Francis <alistair.fran...@wdc.com> > --- > linux-user/uname.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/linux-user/uname.c b/linux-user/uname.c > index 313b79dbad..293b2238f2 100644 > --- a/linux-user/uname.c > +++ b/linux-user/uname.c > @@ -90,6 +90,11 @@ int sys_uname(struct new_utsname *buf) > * struct linux kernel uses). > */ > > +#if defined(CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE) && QEMU_GNUC_PREREQ(9, 0) > +#pragma GCC diagnostic push > +#pragma GCC diagnostic ignored "-Wstringop-truncation" > +#endif
Why do we need the pragma? > + > memset(buf, 0, sizeof(*buf)); We are prezeroing the entire field, at which point... > COPY_UTSNAME_FIELD(buf->sysname, uts_buf.sysname); > COPY_UTSNAME_FIELD(buf->nodename, uts_buf.nodename); ...using strncpy() for a shorter string is wasteful (we're writing the tail end twice), and for a long string is warning-prone. Why not rewrite COPY_UTSNAME_FIELD() to use memcpy() for the MIN(strlen(src), __NEW_UTS_LEN) and drop the write of the trailing NUL, since it will already be NUL from your memset()? -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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