On 17/09/2020 09.18, Paolo Bonzini wrote: > On 17/09/20 08:30, Thomas Huth wrote: >> On 16/09/2020 19.19, Thomas Huth wrote: >>> GCC 9.3.0 on Ubuntu complains: >>> >>> In file included from /usr/include/string.h:495, >>> from /home/travis/build/huth/qemu/include/qemu/osdep.h:87, >>> from ../migration/global_state.c:13: >>> In function ‘strncpy’, >>> inlined from ‘global_state_store_running’ at >>> ../migration/global_state.c:47:5: >>> /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error: >>> ‘__builtin_strncpy’ specified bound 100 equals destination size >>> [-Werror=stringop-truncation] >>> 106 | return __builtin___strncpy_chk (__dest, __src, __len, __bos >>> (__dest)); >>> | >>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> >>> ... but we apparently really want to do the strncpy here. Silence the >>> warning with QEMU_NONSTRING. >>> >>> Signed-off-by: Thomas Huth <th...@redhat.com> >>> --- >>> migration/global_state.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/migration/global_state.c b/migration/global_state.c >>> index 25311479a4..f1355d7d97 100644 >>> --- a/migration/global_state.c >>> +++ b/migration/global_state.c >>> @@ -43,9 +43,9 @@ int global_state_store(void) >>> void global_state_store_running(void) >>> { >>> const char *state = RunState_str(RUN_STATE_RUNNING); >>> + QEMU_NONSTRING char *dest = (char *)global_state.runstate; >>> assert(strlen(state) < sizeof(global_state.runstate)); >>> - strncpy((char *)global_state.runstate, >>> - state, sizeof(global_state.runstate)); >>> + strncpy(dest, state, sizeof(global_state.runstate)); >>> } >> >> Darn, I was sending too fast here, sorry, but seems like this does *not* >> fix the issue with GCC 9.3: >> >> https://travis-ci.com/github/huth/qemu/jobs/385871010#L2930 >> >> ... so maybe we should simply switch to strpadcpy() instead? > > Yes, and probably do so everywhere that strncpy is used.
I think the trick with QEMU_NONSTRING should work fine in all cases where we have a real array, see e.g. buf[] in find_vdi_name() in block/sheepdog.c. It just does not seem to work in case you have a char* pointer instead of an array... Thomas