| Message ID | 20210419140132.16909-7-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen: Switch to using -Og for debug builds | expand |
At 15:01 +0100 on 19 Apr (1618844491), Andrew Cooper wrote: > When compiling at -Og: > > In file included from > /builds/xen-project/people/andyhhp/xen/xen/include/asm/domain.h:4:0, > from /builds/xen-project/people/andyhhp/xen/xen/include/xen/domain.h:8, > from /builds/xen-project/people/andyhhp/xen/xen/include/xen/sched.h:11, > from /builds/xen-project/people/andyhhp/xen/xen/include/xen/ioreq.h:22, > from common.c:23: > common.c: In function '_shadow_prealloc': > /builds/xen-project/people/andyhhp/xen/xen/include/xen/mm.h:252:55: error: 't' may be used uninitialized in this function [-Werror=maybe-uninitialized] > return page != head->next ? pdx_to_page(page->list.prev) : NULL; > ^ > common.c:933:28: note: 't' was declared here > struct page_info *sp, *t; > ^ > > I'm not certain the analysis is correct. 't' is a temporary variable, and is > clearly initialised before use in foreach_pinned_shadow(). Either way, > initialising it to NULL placates the compiler. Yeah, this analysis seems wrong to me too - if nothing else, why does it not complain about the identical code in shadow_blow_tables() below? That said, since the non-debug build doesn't complain here, presumably it will be able to elide this dead store. Acked-by: Tim Deegan <tim@xen.org>
diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c index b99ca14e71..737e6b365a 100644 --- a/xen/arch/x86/mm/shadow/common.c +++ b/xen/arch/x86/mm/shadow/common.c @@ -931,7 +931,7 @@ static inline void trace_shadow_prealloc_unpin(struct domain *d, mfn_t smfn) static void _shadow_prealloc(struct domain *d, unsigned int pages) { struct vcpu *v; - struct page_info *sp, *t; + struct page_info *sp, *t = NULL; mfn_t smfn; int i;
When compiling at -Og: In file included from /builds/xen-project/people/andyhhp/xen/xen/include/asm/domain.h:4:0, from /builds/xen-project/people/andyhhp/xen/xen/include/xen/domain.h:8, from /builds/xen-project/people/andyhhp/xen/xen/include/xen/sched.h:11, from /builds/xen-project/people/andyhhp/xen/xen/include/xen/ioreq.h:22, from common.c:23: common.c: In function '_shadow_prealloc': /builds/xen-project/people/andyhhp/xen/xen/include/xen/mm.h:252:55: error: 't' may be used uninitialized in this function [-Werror=maybe-uninitialized] return page != head->next ? pdx_to_page(page->list.prev) : NULL; ^ common.c:933:28: note: 't' was declared here struct page_info *sp, *t; ^ I'm not certain the analysis is correct. 't' is a temporary variable, and is clearly initialised before use in foreach_pinned_shadow(). Either way, initialising it to NULL placates the compiler. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Tim Deegan <tim@xen.org> CC: Jan Beulich <JBeulich@suse.com> CC: Roger Pau Monné <roger.pau@citrix.com> CC: Wei Liu <wl@xen.org> --- xen/arch/x86/mm/shadow/common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)