[Bug sanitizer/55309] gcc's address-sanitizer 66% slower than clang's

[kcc at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55309

--- Comment #47 from Kostya Serebryany <kcc at gcc dot gnu.org> 2013-02-22 13:52:12 UTC ---
(In reply to comment #46)
> (In reply to comment #43)
> > 400.perlbench fails with a global-buffer-overflow which clang does not detect.
> > I did not investigate why. It could be a gcc false positive or clang false
> > negative.
> 
> On which file/function the global-buffer-overflow was?  Can you send me the
> asan diagnostics?

Interestingly, the symbolization/debuginfo seems to be completely broken :( 

% g++ -g -fsanitize=address ./use-after-free.cc -static-libasan ; ./a.out  2>&1
| grep '#0'
    #0 0x4179c2 (/home/kcc/tmp/a.out+0x4179c2)
    #0 0x40f18a (/home/kcc/tmp/a.out+0x40f18a)
    #0 0x40f26a (/home/kcc/tmp/a.out+0x40f26a)
% addr2line -f -e ./a.out 0x4179c2 0x40f18a 0x40f26a 
main
??:0
free
??:0
malloc
??:0
% 

==580== ERROR: AddressSanitizer: global-buffer-overflow on address
0x00000078e2a5 at pc 0x4e47d7 bp 0x7fffa2fbc7b0 sp 0x7fffa2fbc7a8
READ of size 1 at 0x00000078e2a5 thread T0
    #0 0x4e47d6 in PerlIO_find_layer
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4e47d6)
    #1 0x4e63e6 in PerlIO_default_buffer
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4e63e6)
    #2 0x4e678e in PerlIO_default_layers
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4e678e)
    #3 0x4e7a41 in PerlIO_resolve_layers
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4e7a41)
    #4 0x4e8145 in PerlIO_openn
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4e8145)
    #5 0x4f5d32 in PerlIO_open
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4f5d32)
    #6 0x4dd808 in S_open_script
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4dd808)
    #7 0x4d3be6 in S_parse_body
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4d3be6)
    #8 0x4d2a4b in perl_parse
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4d2a4b)
    #9 0x4f6ee8 in main
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4f6ee8)
    #10 0x7fd3a245376c (/lib/x86_64-linux-gnu/libc.so.6+0x2176c)
    #11 0x4037d8
(benchspec/CPU2006/400.perlbench/run/run_base_train_z.0000/perlbench_base.z+0x4037d8)
0x00000078e2a5 is located 0 bytes to the right of global variable '*.LC50
(perlio.c)' (0x78e2a0) of size 5
  '*.LC50 (perlio.c)' is ascii string 'unix'
SUMMARY: AddressSanitizer: global-buffer-overflow ??:0 PerlIO_find_layer




> 
> > 464.h264ref is VERY slow, I did not look why.
> 
> And it didn't fail on that:
>     for (dd=d[k=0]; k<16; dd=d[++k])
>     {
>       satd += (dd < 0 ? -dd : dd);
>     }
> or have you fixed that up in your SPEC sources?

Interestingly, no. I haven't touched SPEC sources here. 
Maybe gcc does full unroll thus eliminating the buggy read (I did not check).