Messages in this thread | | | Date | Fri, 7 Sep 2018 16:13:50 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] perf: enum overflow in uapi/linux/perf_event.h |
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On Fri, Sep 07, 2018 at 03:58:17PM +0200, Peter Zijlstra wrote: > On Fri, Sep 07, 2018 at 01:50:18PM +0000, Christophe Leroy wrote: > > > > > > On 09/07/2018 01:42 PM, Peter Zijlstra wrote: > > > On Fri, Sep 07, 2018 at 01:27:19PM +0000, Christophe Leroy wrote: > > > > On PPC32, enums are 32 bits, so __PERF_SAMPLE_CALLCHAIN_EARLY is > > > > out of scope. The following sparse warning is encountered: > > > > > > > > CHECK arch/powerpc/kernel/process.c > > > > ./include/uapi/linux/perf_event.h:147:56: warning: cast truncates bits from constant value (8000000000000000 becomes 0) > > > > > > Urgh... what compiler is that? I've not seen anything like that from the > > > build bots. > > > > > > > [root@pc16082vm linux-powerpc]# sparse --version > > 0.5.2 > > > > [root@pc16082vm linux-powerpc]# ppc-linux-gcc --version > > ppc-linux-gcc (GCC) 5.4.0 > > Ah, that's a sparse warning. But does your GCC agree? The thing is, > sparse uses the C enum spec, but I suspect GCC uses the C++ enum spec > and it all works fine.
What does the below proglet print on your PPC32 box? I suspect the output will be:
400000000000
and all is well.
--- #include <stdio.h>
enum ponies { big = 1ULL<<46, };
int main(int argc, char **argv) { unsigned long long val = big; printf("%Lx\n", val); return 0; }
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