On 2017-11-25 12:00:15 -0800, Andres Freund wrote: > Hi, > > On 2017-11-25 14:50:41 -0500, Tom Lane wrote: > > I wrote: > > > Tomas Vondra <[email protected]> writes: > > >> BTW I also see these failures in hstore: > > > > >> ==15168== Source and destination overlap in memcpy(0x5d0fed0, 0x5d0fed0, > > >> 40) > > >> ==15168== at 0x4C2E00C: memcpy@@GLIBC_2.14 (vg_replace_strmem.c:1018) > > >> ==15168== by 0x15419A06: hstoreUniquePairs (hstore_io.c:343) > > >> ==15168== by 0x15419EE4: hstore_in (hstore_io.c:416) > > > > > Huh ... > > > > I tried to duplicate this on my RHEL6 workstation, and failed to, > > even though adding an assertion easily proves that the hstore > > regression test does exercise the case. So apparently the answer > > as to why skink isn't reporting this is just "not all versions of > > valgrind check it". > > I suspect that the issue rather is that the compiler will sometimes > replace the memcpy() with an in-line member-by-member version. That'll > not be visible as a memcpy to valgrind.
That's indeed the case. Here's the disassembly from skink, albeit for v10, because those objects were currently present: disassemble /s hstoreUniquePairs ... 342 res++; 0x00000000000005c2 <+174>: add $0x28,%rbx 343 memcpy(res, ptr, sizeof(Pairs)); 0x00000000000005c6 <+178>: mov (%r12),%rax 0x00000000000005ca <+182>: mov 0x8(%r12),%rdx 0x00000000000005cf <+187>: mov %rax,(%rbx) 0x00000000000005d2 <+190>: mov %rdx,0x8(%rbx) 0x00000000000005d6 <+194>: mov 0x10(%r12),%rax 0x00000000000005db <+199>: mov 0x18(%r12),%rdx 0x00000000000005e0 <+204>: mov %rax,0x10(%rbx) 0x00000000000005e4 <+208>: mov %rdx,0x18(%rbx) 0x00000000000005e8 <+212>: mov 0x20(%r12),%rax 0x00000000000005ed <+217>: mov %rax,0x20(%rbx) 344 } 345 ... Greetings, Andres Freund
