On 2019-10-08 12:44, William Tu wrote:
On Tue, Oct 08, 2019 at 10:04:17AM -0700, David Wilder wrote:
Since commit e2ed6fbeb1, Ci on ppc64le with Ubuntu 16.04.6 LTS throws
this error:
lib/fatal-signal.c: In function 'send_backtrace_to_monitor':
lib/fatal-signal.c:168:9: error: variable 'dep' might be clobbered by
'longjmp' or 'vfork' [-Werror=clobbered]
int dep;
Declaring dep as a volatile int.
Signed-off-by: David Wilder <[email protected]>
---
lib/fatal-signal.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c
index 7733850d5..09f7c6ecf 100644
--- a/lib/fatal-signal.c
+++ b/lib/fatal-signal.c
@@ -165,7 +165,8 @@ fatal_signal_add_hook(void (*hook_cb)(void *aux),
void (*cancel_cb)(void *aux),
*/
static inline void
send_backtrace_to_monitor(void) {
- int dep;
+ /* volatile added to prevent a "clobbered" error on ppc64le with
gcc */
+ volatile int dep;
struct unw_backtrace unw_bt[UNW_MAX_DEPTH];
unw_cursor_t cursor;
unw_context_t uc;
--
2.23.0.162.gf1d4a28
Thank you for testing it on ppc64!
I'm not able to reproduce the issue on x86_64.
And I don't understand where do we call setjmp and longjmp?
Is it the case that:
unw_getcontext/unw_init_local is calling setjmp
and
unw_get_reg/unw_get_proc_name is calling longjmp while it's
scanning back the stack?
Looking at the source code of libunwind, I couldn't quite
understand how setjmp/longjmp is used here.
Regards,
William
Hi William
This is an issue with gcc incorrectly generating the warning. I found
reports against gcc for this issue. I tried but was unable to isolate
the problem to a gcc version. Gcc v8.2.1 in rhel8 did not have the
problem, however v8 in ubuntu 16.04 still had the issue. As I was
unable to flag the version gcc I chose this solution over a #pragma.
PS: I recently starting running Ci against ppc64le, travis_ci.org is now
supporting (in beta) ppc64le. I hope to soon push changes to enable a
ppc64le Ci for ovs.
Regards
David
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