GC buckets in 2.067

[Iain Buclaw via Digitalmars-d]

When running the unittest program for druntime.

---
Program received signal SIGSEGV, Segmentation fault.
__memset_avx2 () at ../sysdeps/x86_64/multiarch/memset-avx2.S:101

backtrace:
#0  __memset_avx2 () at ../sysdeps/x86_64/multiarch/memset-avx2.S:101
#1  0x00000000004d45a0 in gc.gc.GC.malloc(ulong, uint, ulong*,
const(TypeInfo)) (this=..., size=8, bits=0, alloc_size=0x7fffffffd428,
ti=0x714050 <TypeInfo_PS2rt3aaA4Impl.init$>) at
../../../../dev/libphobos/libd
runtime/gc/gc.d:459
#2  0x00000000004c5948 in gc_qalloc (sz=8, ba=0, ti=0x714050
<TypeInfo_PS2rt3aaA4Impl.init$>) at
../../../../dev/libphobos/libdruntime/gc/proxy.d:196
#3  0x00000000004450de in core.memory.GC.qalloc(ulong, uint,
const(TypeInfo)) (sz=8, ba=0, ti=0x714050 <TypeInfo_PS2rt3aaA4Impl.init$>)
at ../../../../dev/libphobos/libdruntime/core/memory.d:368
#4  0x0000000000420e31 in _d_newitemT (_ti=0x714050
<TypeInfo_PS2rt3aaA4Impl.init$>) at
../../../../dev/libphobos/libdruntime/rt/lifetime.d:1096
#5  0x0000000000411f6c in _aaGetX (aa=0x7ffff7ed2090, keyti=0x7191a0
<ClassInfo for core.thread.Thread>, valuesize=8, pkey=0x7fffffffd598) at
../../../../dev/libphobos/libdruntime/rt/aaA.d:172
#6  0x0000000000449f6d in core.thread.ThreadGroup.create(void() delegate)
(this=0x7ffff7ed2080, dg=...) at
../../../../dev/libphobos/libdruntime/core/thread.d:3318
#7  0x00000000004c28ed in core.sync.mutex.__unittestL241_1() () at
../../../../dev/libphobos/libdruntime/core/sync/mutex.d:262
#8  0x0000000000445a7b in __foreachbody3 (this=0x7fffffffd790, m=0x71a9e0
<ModuleInfo for core.sync.mutex>) at
../../../../dev/libphobos/libdruntime/core/runtime.d:448
#9  0x0000000000407c1e in object.ModuleInfo.__lambda2 (this=0x7fffffffd750,
m=0x71a9e0 <ModuleInfo for core.sync.mutex>) at
../../../../dev/libphobos/libdruntime/object.d:1771
#10 0x000000000041c58d in rt.minfo.moduleinfos_apply(scope
int(immutable(object.ModuleInfo*)) delegate) (dg=...) at
../../../../dev/libphobos/libdruntime/rt/minfo.d:287
#11 0x0000000000407beb in object.ModuleInfo.opApply(scope
int(object.ModuleInfo*) delegate) (dg=...) at
../../../../dev/libphobos/libdruntime/object.d:1770
#12 0x00000000004457fa in runModuleUnitTests () at
../../../../dev/libphobos/libdruntime/core/runtime.d:438
#13 0x000000000041ab36 in runAll (this=0x7fffffffdbe0) at
../../../../dev/libphobos/libdruntime/rt/dmain2.d:428
#14 0x000000000041aad2 in rt.dmain2._d_run_main(int, char**, extern(C)
int(char[][]) function*).tryExec(scope void() delegate)
(this=0x7fffffffdbe0, dg=...) at
../../../../dev/libphobos/libdruntime/rt/dmain2.d:40
4
#15 0x000000000041aa2b in _d_run_main (argc=1, argv=0x7fffffffdd68,
mainFunc=0x402a60 <D main>) at
../../../../dev/libphobos/libdruntime/rt/dmain2.d:437
#16 0x00007ffff6ee6a40 in __libc_start_main (main=0x402910 <main>, argc=1,
argv=0x7fffffffdd68, init=<optimised out>, fini=<optimised out>,
rtld_fini=<optimised out>, stack_end=0x7fffffffdd58) at libc-start.c:289
#17 0x0000000000402969 in _start ()

In gc.d
---
 459├>            memset(p + size, 0, *alloc_size - size);

p = (void *) 0x4c9fad <__gdc_exception_cleanup>
---

So the GC is trying to run memset on the address of a function.

It's caused by this line:

1796│         // Return next item from free list
1797├>        bucket[bin] = (cast(List*)p).next;

Where:

*(cast(List*)p) = {next = 0x4c9fad <__gdc_exception_cleanup>, pool = 0x0}


Not sure what is going on, but it seems to happen after allocating memory a
couple dozen or so times.

David, did you get anything like this when moving to 2.067?
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