Bad complex descriptor occurs rarely in find-leak mode about bdwgc

[ivmai]

#1  0x00007fb1c9808859 in __GI_abort () at abort.c:79
#2  0x00007fb1c9a2a923 in GC_push_complex_descriptor (addr=addr@entry=0x7fb1bdfca000, complex_d=<optimized out>,
    msp=msp@entry=0x7fb1c6f9de90, msl=msl@entry=0x7fb1c6fade90) at extra/../typd_mlc.c:623
#3  0x00007fb1c9a2aa9f in GC_array_mark_proc (addr=0x7fb1bdfca000, mark_stack_ptr=0x7fb1c6f9de90,
    mark_stack_limit=0x7fb1c6fadea0, env=<optimized out>) at extra/../typd_mlc.c:653
#4  0x00007fb1c9a2e916 in GC_mark_from (mark_stack_top=<optimized out>, mark_stack_top@entry=0x7fb1c6f9deb0,
    mark_stack=mark_stack@entry=0x7fb1c6f9dea0, mark_stack_limit=mark_stack_limit@entry=0x7fb1c6fadea0)
    at extra/../mark.c:711
#5  0x00007fb1c9a3dca1 in GC_do_local_mark (local_mark_stack=0x7fb1c6f9dea0, local_top=0x7fb1c6f9deb0)
    at extra/../mark.c:1005
#6  0x00007fb1c9a3dee9 in GC_mark_local (local_mark_stack=local_mark_stack@entry=0x7fb1c6f9dea0, id=5)
    at extra/../mark.c:1136
#7  0x00007fb1c9a3e1a9 in GC_help_marker (my_mark_no=893) at extra/../mark.c:1195
#8  0x00007fb1c9a3e325 in GC_mark_thread (id=<optimized out>) at extra/../pthread_support.c:466
#9  GC_mark_thread (id=<optimized out>) at extra/../pthread_support.c:415
#10 0x00007fb1c99e6609 in start_thread (arg=<optimized out>) at pthread_create.c:477

(gdb) fr 3
(gdb) p nwords
$4 = 3004
(gdb) p *(complex_descriptor*)addr[nwords-1]
$8 = {ld = {ld_tag = 140401415094208, ld_size = 140401388137088, ld_nelements = 0, ld_descriptor = 0}, ad = {
    ad_tag = 140401415094208, ad_nelements = 140401388137088, ad_element_descr = 0x0}, sd = {sd_tag = 140401415094208,
    sd_first = 0x7fb1beddaa80, sd_second = 0x0}}

But ld_tag should be 3 (tags are in range 1..3)

Currently unclear whether the ptr to descriptor is corrupted or the descriptor itself.

[ivmai]

Not reproduced with -O0
Not reproduced with -D GC_DISABLE_INCREMENTAL
Reproduced with -D NO_SOFT_VDB

[ivmai]

Source: master (5839684)
Build: https://app.travis-ci.com/github/ivmai/bdwgc/jobs/608674850
Host: Linux/amd64
Config: CFLAGS_EXTRA="-D _FORTIFY_SOURCE=2 -D FIND_LEAK -D SKIP_LEAKED_OBJECTS_PRINTING" CONF_OPTIONS="--enable-gc-assertions --enable-cplusplus"