On 2015-12-19 15:03, Niko Tyni wrote: > On Tue, Nov 24, 2015 at 04:24:54PM +0000, Jean-Michel Vourgère wrote: > > Control: tags -1 + help > > > > Antonio Terceiro wrote: > > > "make check-TESTS" fails > > > > I tested previous version on mips, and it now FTBFS too. It used to work > > ok. [1] (thanks Tobias, upstream, for suggesting that.) > > > > So I suppose it is related to another package. > > > > I tried compiling with good old gcc 4.9 and I get the same error in 1.5.4. > > It's a latent bug in rrdtool that triggered with libc6 2.19-20 on mips. > > The test suite failure in tests/tune2 boils down to > > rrdtool tune --beta 0.4 tests/tune2-testorg.rrd > > zeroing out a big part of the file in addition to changing a single byte > like it's supposed to. It's easy to see by calling > > rrdtool dump tests/tune2-testorg.rrd >/dev/null > > which starts to fail with stderr > > ERROR: unknown consolidation function '' > > on a corrupted file. > > This started to happen with libc6 2.19-20, as tested by compiling rrdtool > 1.5.5 on jessie and running with LD_LIBRARY_PATH pointing to different > libc.so.6 versions. > > The problem is that rrd_write() ends up calling memcpy(3) on overlapping > memory areas, which is explicitly prohibited in its documentation. With > libc6 2.19-20 on mips, this started zeroing out part of the areas under > some conditions. The attached testcase triggers it at least on minkus.d.o, > tested with something like > > #!/bin/bash > dd if=/dev/urandom of=testfile.orig bs=1024 count=1 > gcc t.c > cp testfile.orig testfile > ./a.out testfile > diff -u <(od -x testfile.orig) <(od -x testfile) > > which normally doesn't show any differences. I'm cc'ing the libc6 > maintainers, not sure how intentional this change of behaviour is.
The change is likely due to the switch to the MIPS32R2 ISA on mips. A different code is used, so with a different undefined behaviour. > Backtrace for the rrd_write() call that triggers it: > > #0 rrd_write (rrd_file=0x41d038, buf=0x77fef168, count=560) at > rrd_open.c:798 > #1 0x77f65888 in rrd_tune (argc=4, argv=0x7fff6648) at rrd_tune.c:395 > #2 0x00402f44 in HandleInputLine (argc=5, argv=0x7fff6644, out=0x77f56900 > <_IO_2_1_stderr_>) at rrd_tool.c:800 > #3 0x00400f10 in main (argc=5, argv=0x7fff6644) at rrd_tool.c:545 > > (gdb) print ((rrd_simple_file_t *) rrd_file->pvt)->file_start + > rrd_file->pos > $6 = 0x77fef168 "HWPREDICT" > > (gdb) print (char *)buf > $8 = 0x77fef168 "HWPREDICT" > > A workaround is to configure with --disable-mmap, except that seems > to break tests/tune1 on all architectures (at least amd64 and mips). > I haven't looked into that. Can't you replace memcpy calls with overlapping areas with a memmove instead? Even if the testsuite looks fine you will definitely have some corruptions with memcpy and overlapping area on other architectures too. Aurelien -- Aurelien Jarno GPG: 4096R/1DDD8C9B aurel...@aurel32.net http://www.aurel32.net
