On Mon, Jul 1, 2013 at 4:08 AM, Alexey Bazhin <b...@irc.msk.ru> wrote:
> Hi!
>
> I would like to report a bug in volk on armv6.
>
> There is infinite "while" cycle in volk/tmpl/volk_cpu.tmpl.c function
> "has_neon" (line 111).
>
> Code "while(!found_neon && auxvec_f) {" will loop infinitely if there
> is no neon in platform. found_neon will never be true and file
> descriptor auxvec_f will always be true.
>
> --
> Alexey Bazhin <b...@irc.msk.ru>
Ok, I see your point. Looks like we should be testing the return value
from fread, instead of auxvec_f. Can you confirm if this patch works?
diff --git a/volk/tmpl/volk_cpu.tmpl.c b/volk/tmpl/volk_cpu.tmpl.c
index 81fc679..b1a0a4a 100644
--- a/volk/tmpl/volk_cpu.tmpl.c
+++ b/volk/tmpl/volk_cpu.tmpl.c
@@ -116,10 +116,11 @@ static int has_neon(void){
auxvec_f = fopen("/proc/self/auxv", "rb");
if(!auxvec_f) return 0;
+ size_t r = 1;
//so auxv is basically 32b of ID and 32b of value
//so it goes like this
- while(!found_neon && auxvec_f) {
- fread(auxvec, sizeof(unsigned long), 2, auxvec_f);
+ while(!found_neon && r) {
+ r = fread(auxvec, sizeof(unsigned long), 2, auxvec_f);
if((auxvec[0] == AT_HWCAP) && (auxvec[1] & HWCAP_NEON))
found_neon = 1;
}
Or might be better to test 'if(r < 2)' after the fread line and break
in case an error occurs and we only get 1 character out and not try to
read from it again. Probably not a bit deal since we're only reading
in two chars at a time.
Tom
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