https://issues.dlang.org/show_bug.cgi?id=23978

Iain Buclaw <ibuclaw@gdcproject.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ibuclaw@gdcproject.org

--- Comment #1 from Iain Buclaw <ibuclaw@gdcproject.org> ---
(gdb) bt
#0  0x00005644ce0c033d in
_D3dmd4root3aav15dmd_aaGetRvalueFNaNbNiPSQBnQBmQBk2AAPvZQd (key=0x7f9ec39f5560,
aa=0x7f9ec265d360) at src/dmd/root/aav.d:127
#1  0x00005644ce0c0660 in
_D3dmd4root3aav__T10AssocArrayTCQBe10identifier10IdentifierTCQCh7dsymbol7DsymbolZQCl7opIndexMFNaNbNixCQDwQCsQCjZQCa
(this=..., key=0x7f9ec39f5560) at src/dmd/root/aav.d:313
#2  0x00005644cdf373fc in DsymbolTable::lookup(Identifier const*)
(this=0x7f9ec2ec08c0, ident=0x7f9ec39f5560) at src/dmd/dsymbol.d:2399
#3  0x00005644cdf3509a in ScopeDsymbol::search(Loc const&, Identifier*, int)
(this=0x7f9ec39f8400, loc=..., ident=0x7f9ec39f5560, flags=8) at
src/dmd/dsymbol.d:1474
#4  0x00005644cdf31890 in StructDeclaration::search(Loc const&, Identifier*,
int) (this=0x7f9ec39f8400, loc=..., ident=0x7f9ec39f5560, flags=8) at
src/dmd/dstruct.d:277
#5  0x00005644ce008817 in
_D3dmd6opover15search_functionFCQBe7dsymbol12ScopeDsymbolCQCe10identifier10IdentifierZCQDhQCd7Dsymbol
(funcid=0x7f9ec39f5560, ad=0x7f9ec39f8400) at src/dmd/opover.d:1435
#6  0x00005644cdf30d97 in search_toString(StructDeclaration*)
(sd=0x7f9ec39f8400) at src/dmd/dstruct.d:51
#7  0x00005644ce030afd in semanticTypeInfoMembers(StructDeclaration*)
(sd=0x7f9ec39f8400) at src/dmd/semantic3.d:1650
#8  0x00005644ce03086c in Semantic3Visitor::visit(AggregateDeclaration*)
(this=0x7ffd1ab29230, ad=0x7f9ec39f8400) at src/dmd/semantic3.d:1590
#9  0x00005644ce026566 in
ParseTimeVisitor<ASTCodegen>::visit(StructDeclaration*) (this=0x7ffd1ab29230,
s=0x7f9ec39f8400) at src/dmd/parsetimevisitor.d:88
#10 0x00005644cdf31f6e in StructDeclaration::accept(Visitor*)
(this=0x7f9ec39f8400, v=0x7ffd1ab29230) at src/dmd/dstruct.d:490
#11 0x00005644ce02b736 in semantic3(Dsymbol*, Scope*) (dsym=0x7f9ec39f8400,
sc=0x7f9ec317f2e0) at src/dmd/semantic3.d:83
#12 0x00005644cdf98f02 in ExpressionSemanticVisitor::visit(DeclarationExp*)
(this=0x7ffd1ab293a8, e=0x7f9ec39f1c00) at src/dmd/expressionsem.d:5471
#13 0x00005644cdf7dae2 in DeclarationExp::accept(Visitor*)
(this=0x7f9ec39f1c00, v=0x7ffd1ab293a8) at src/dmd/expression.d:4212
#14 0x00005644cdfafe44 in expressionSemantic(Expression*, Scope*)
(e=0x7f9ec39f1c00, sc=0x7f9ec317f2e0) at src/dmd/expressionsem.d:12566
#15 0x00005644ce0361e8 in StatementSemanticVisitor::visit(ExpStatement*)
(this=0x7ffd1ab29458, s=0x7f9ec39f1bd0) at src/dmd/statementsem.d:206
#16 0x00005644ce032736 in ExpStatement::accept(Visitor*) (this=0x7f9ec39f1bd0,
v=0x7ffd1ab29458) at src/dmd/statement.d:490
#17 0x00005644ce0360cc in statementSemantic(Statement*, Scope*)
(s=0x7f9ec39f1bd0, sc=0x7f9ec317f2e0) at src/dmd/statementsem.d:148
#18 0x00005644ce0364af in StatementSemanticVisitor::visit(CompoundStatement*)
(this=0x7ffd1ab29778, cs=0x7f9ec39f1c30) at src/dmd/statementsem.d:269
#19 0x00005644ce032c5a in CompoundStatement::accept(Visitor*)
(this=0x7f9ec39f1c30, v=0x7ffd1ab29778) at src/dmd/statement.d:633
#20 0x00005644ce0360cc in statementSemantic(Statement*, Scope*)
(s=0x7f9ec39f1c30, sc=0x7f9ec317f2e0) at src/dmd/statementsem.d:148
#21 0x00005644ce02cd57 in Semantic3Visitor::visit(FuncDeclaration*)
(this=0x7ffd1ab2a220, funcdecl=0x7f9ec39f7cc0) at src/dmd/semantic3.d:598
#22 0x00005644cdfbb2ca in FuncDeclaration::accept(Visitor*)
(this=0x7f9ec39f7cc0, v=0x7ffd1ab2a220) at src/dmd/func.d:2857
#23 0x00005644ce02b736 in semantic3(Dsymbol*, Scope*) (dsym=0x7f9ec39f7cc0,
sc=0x7f9ec317dcf0) at src/dmd/semantic3.d:83
#24 0x00005644ce02bb87 in Semantic3Visitor::visit(Module*)
(this=0x7ffd1ab2a2e0, mod=0x7f9ec39f7000) at src/dmd/semantic3.d:205
#25 0x00005644cdf1a31e in Module::accept(Visitor*) (this=0x7f9ec39f7000,
v=0x7ffd1ab2a2e0) at src/dmd/dmodule.d:1259
#26 0x00005644ce02b736 in semantic3(Dsymbol*, Scope*) (dsym=0x7f9ec39f7000,
sc=0x0) at src/dmd/semantic3.d:83
#27 0x00005644cdea0e55 in _D3dmd4mars7tryMainFmPPxaKSQz7globals5ParamZi
(params=..., argv=0x7ffd1ab2abe8, argc=5) at src/dmd/mars.d:473
#28 0x00005644cdea2a9a in _Dmain (_param_0=...) at src/dmd/mars.d:962
#29 0x00005644ce1ddabb in rt.dmain2._d_run_main2(char[][], ulong, extern(C)
int(char[][]) function).runAll().__lambda2() ()
#30 0x00005644ce1dd96a in rt.dmain2._d_run_main2(char[][], ulong, extern(C)
int(char[][]) function).tryExec(scope void() delegate) ()
#31 0x00005644ce1dda43 in rt.dmain2._d_run_main2(char[][], ulong, extern(C)
int(char[][]) function).runAll() ()
#32 0x00005644ce1dd96a in rt.dmain2._d_run_main2(char[][], ulong, extern(C)
int(char[][]) function).tryExec(scope void() delegate) ()
#33 0x00005644ce1dd8d3 in _d_run_main2 ()
#34 0x00005644ce1dd69c in _d_run_main ()
#35 0x00005644cdea2a58 in main (argc=5, argv=0x7ffd1ab2abe8) at
src/dmd/mars.d:918

--

https://issues.dlang.org/show_bug.cgi?id=23978

--- Comment #2 from Iain Buclaw <ibuclaw@gdcproject.org> ---
---
125│         while (e)
126│         {
127├───────────> if (key == e.key)
128│                 return e.value;
129│             e = e.next;
130│         }
---

(gdb) p key
$1 = (void *) 0x7f9ec39f5560

(gdb) p e
$2 = (dmd.root.aav.aaA *) 0x20ec8348ec8b4855

(gdb) p aa.b[i]
$3 = (dmd.root.aav.aaA *) 0x7f9ec2666a00

(gdb) p *aa.b[i]
$4 = {next = 0x5644ce2fb510 <vtable for dmd.declaration.ThisDeclaration>,
keyValue = {key = 0x7f9ec39ec5e0, value = 0x7f9ec2642660}}

(gdb) p *('dmd.declaration.ThisDeclaration'*)aa.b[i]
$5 = {<dmd.declaration.VarDeclaration> = {<dmd.declaration.Declaration> =
{<dmd.dsymbol.Dsymbol> = {<dmd.ast_node.ASTNode> =
{<dmd.root.rootobject.RootObject> = {<No data fields>}, <No data fields>},
        ident = 0x7f9ec39ec5e0, parent = 0x7f9ec2642660, csym = 0x0, loc =
{filename = 0x0, linnum = 0, charnum = 0}, _scope = 0x0, prettystring = 0x0,
atts = 0x0, errors = false,
        semanticRun = 2 '\002', localNum = 0}, type = 0x7f9ec265d660,
originalType = 0x7f9ec265d660, storage_class = 268697636, visibility = {kind =
5 '\005', pkg = 0x0}, _linkage = 1 '\001', inuse = 0,
      adFlags = 0 '\000', isym = 0x0, mangleOverride = 0x0}, _init = 0x0,
nestedrefs = {length = 0, data = 0x0, smallarray = {0x0}}, aliasTuple = 0x0,
lastVar = 0x0, edtor = 0x0, range = 0x0,
    maybes = 0x0, endlinnum = 0, offset = 0, sequenceNumber = 610, alignment =
{value = 1234, pack = false}, ctfeAdrOnStack = 4294967295, bitFields = 256,
canassign = 0 '\000',
    isdataseg = 2 '\002'}, <No data fields>}

(gdb) p *(('dmd.declaration.ThisDeclaration'*)aa.b[i]).ident
$6 = {<dmd.root.rootobject.RootObject> = {<No data fields>}, value = 88,
isAnonymous_ = false, name = "this"}

(gdb) p *(('dmd.declaration.ThisDeclaration'*)aa.b[i]).type
$7 = {<dmd.ast_node.ASTNode> = {<dmd.root.rootobject.RootObject> = {<No data
fields>}, <No data fields>}, ty = 8 '\b', mod = 1 '\001', deco = 0x7f9ec37e8500
"xS8pr1101138raytraceFZ1V",
  mcache = 0x7f9ec2649b40, pto = 0x0, rto = 0x0, arrayof = 0x0, vtinfo = 0x0,
ctype = 0x0}

--

https://issues.dlang.org/show_bug.cgi?id=23978

mhh <maxhaton@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |maxhaton@gmail.com

--- Comment #3 from mhh <maxhaton@gmail.com> ---
Is dip1021 required?

--

https://issues.dlang.org/show_bug.cgi?id=23978

--- Comment #4 from Iain Buclaw <ibuclaw@gdcproject.org> ---
It looks like one of the elements in the aaA array is pointing as a live class object ThisDeclaration. So it's loaded with bogus data and results in a segfault after dereferencing a part of memory it shouldn't have.

--

https://issues.dlang.org/show_bug.cgi?id=23978

--- Comment #5 from Iain Buclaw <ibuclaw@gdcproject.org> ---
(In reply to mhh from comment #3)
> Is dip1021 required?

AFAICT, all that dip1021 is doing is make the compiler call GC.malloc/GC.free a number of times more often than it usually does.

https://github.com/dlang/dmd/blob/master/compiler/src/dmd/ob.d

I'd consider the main trigger to be `-lowmem` - so it may well be the GC itself that is at fault, given that git blame points to a change in `_d_newclass`, this seems the most plausible explanation.

--

https://issues.dlang.org/show_bug.cgi?id=23978

--- Comment #6 from Iain Buclaw <ibuclaw@gdcproject.org> ---
git blame says the regressing commit is https://github.com/dlang/dmd/pull/14837

--

https://issues.dlang.org/show_bug.cgi?id=23978

Iain Buclaw <ibuclaw@gdcproject.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |https://github.com/dlang/dm
                   |                            |d/pull/14837

--

https://issues.dlang.org/show_bug.cgi?id=23978

Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dlang-bugzilla@thecybershad
                   |                            |ow.net

--- Comment #7 from Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> ---
I have not been able to reproduce this. It would be good to have a test case which more reliably reproduces the bug. I tried wrapping the code into a static foreach, but that did not help.

--

https://issues.dlang.org/show_bug.cgi?id=23978

--- Comment #8 from Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> ---
Also because we need something to put in the test suite to prevent this from regressing again.

--

https://issues.dlang.org/show_bug.cgi?id=23978

--- Comment #9 from Iain Buclaw <ibuclaw@gdcproject.org> ---
The printf dumps really don't give any hint as to what went wrong, but there is at least a common pattern I see for each time it crashes.

---------------------

Mem.xrealloc((nil), 624) = 0x7f3686b63000  <-- !!! This address ends up as aa.b
...
...
Mem.xrealloc(0x7f3686b63000, 832) = 0x7f3686b8d400 <-- !!! marked free
...
...
----------------------------------------------------------
from: dmd_aaRehash++
this = 0x7f3686b95a20
nodes = 9
b_length = 4
[
        b[0] 0x7f3686b95a38 = 0x7f3686b95a58 {
                next = 0x7f3686b98c20
                key = 0x7f3687f32fc0
                value = 0x7f3687f2c500
        }
        b[1] 0x7f3686b95a40 = 0x7f3686b98bc0 {
                next = (nil)
                key = 0x7f3687f36060
                value = 0x7f3687f37000
        }
        b[2] 0x7f3686b95a48 = 0x7f3686b98b80 {
                next = 0x7f3686b98be0
                key = 0x7f3687f32fe0
                value = 0x7f3687f2c600
        }
        b[3] 0x7f3686b95a50 = 0x7f3686b98ba0 {
                next = 0x7f3686b98c00
                key = 0x7f3687f36000
                value = 0x7f3687f2c700
        }
]
Mem.xmalloc(768) = 0x7f3686b63000 <-- !!! rehash wants memory, reuse old
address
----------------------------------------------------------
from: dmd_aaRehash--
this = 0x7f3686b95a20
nodes = 9
b_length = 32
[
        b[0] 0x7f3686b63000 = (nil)
        b[1] 0x7f3686b63008 = (nil)
        b[2] 0x7f3686b63010 = (nil)
        b[3] 0x7f3686b63018 = (nil)
        b[4] 0x7f3686b63020 = (nil)
        b[5] 0x7f3686b63028 = (nil)
        b[6] 0x7f3686b63030 = (nil)
        b[7] 0x7f3686b63038 = (nil)  <-- !!! This index is null
        b[8] 0x7f3686b63040 = (nil)
        b[9] 0x7f3686b63048 = (nil)
        b[10] 0x7f3686b63050 = (nil)
        b[11] 0x7f3686b63058 = (nil)
        b[12] 0x7f3686b63060 = (nil)
        b[13] 0x7f3686b63068 = (nil)
        b[14] 0x7f3686b63070 = (nil)
        b[15] 0x7f3686b63078 = (nil)
        b[16] 0x7f3686b63080 = (nil)
        b[17] 0x7f3686b63088 = (nil)
        b[18] 0x7f3686b63090 = (nil)
        b[19] 0x7f3686b63098 = 0x7f3686b98ba0 {
                next = (nil)
                key = 0x7f3687f36000
                value = 0x7f3687f2c700
        }
        b[20] 0x7f3686b630a0 = 0x7f3686b95a58 {
                next = (nil)
                key = 0x7f3687f32fc0
                value = 0x7f3687f2c500
        }
        b[21] 0x7f3686b630a8 = 0x7f3686b98bc0 {
                next = (nil)
                key = 0x7f3687f36060
                value = 0x7f3687f37000
        }
        b[22] 0x7f3686b630b0 = 0x7f3686b98b80 {
                next = (nil)
                key = 0x7f3687f32fe0
                value = 0x7f3687f2c600
        }
        b[23] 0x7f3686b630b8 = 0x7f3686b98c00 {
                next = (nil)
                key = 0x7f3687f36040
                value = 0x7f3687f37330
        }
        b[24] 0x7f3686b630c0 = 0x7f3686b98c20 {
                next = (nil)
                key = 0x7f3687f360a0
                value = 0x7f3687f2c800
        }
        b[25] 0x7f3686b630c8 = (nil)
        b[26] 0x7f3686b630d0 = 0x7f3686b98be0 {
                next = (nil)
                key = 0x7f3687f36080
                value = 0x7f3687f34200
        }
        b[27] 0x7f3686b630d8 = (nil)
        b[28] 0x7f3686b630e0 = 0x7f3686b98c60 {
                next = (nil)
                key = 0x7f3687f360e0
                value = (nil)
        }
        b[29] 0x7f3686b630e8 = (nil)
        b[30] 0x7f3686b630f0 = 0x7f3686b98c40 {
                next = (nil)
                key = 0x7f3687f360c0
                value = 0x7f3687f37660
        }
        b[31] 0x7f3686b630f8 = (nil)
]
...
...
Mem.xmalloc(80) = 0x7f3686ba2b40
----------------------------------------------------------
from: dmd_aaGet
this = 0x7f3686ba2b40
nodes = 0
----------------------------------------------------------
from: dmd_aaGet==
this = 0x7f3686ba2b40
nodes = 1
b_length = 4
[
        b[0] 0x7f3686ba2b58 = (nil)
        b[1] 0x7f3686ba2b60 = 0x7f3686ba2b78 {
                next = (nil)
                key = 0x7f3687f285e0
                value = (nil)
        }
        b[2] 0x7f3686ba2b68 = (nil)
        b[3] 0x7f3686ba2b70 = (nil)
]
----------------------------------------------------------
from: dmd_aaGet
this = 0x7f3686ba2b40
nodes = 1
b_length = 4
[
        b[0] 0x7f3686ba2b58 = (nil)
        b[1] 0x7f3686ba2b60 = 0x7f3686ba2b78 {
                next = (nil)
                key = 0x7f3687f285e0
                value = 0x7f3686b9fb00  <-- !!! This is what corrupts aa.b[7]
        }
        b[2] 0x7f3686ba2b68 = (nil)
        b[3] 0x7f3686ba2b70 = (nil)
]
...
...
----------------------------------------------------------
from: dmd_aaGetRvalue
this = 0x7f3686ba2b40  <-- !!! Last access of this AA
nodes = 2
b_length = 4
[
        b[0] 0x7f3686ba2b58 = (nil)
        b[1] 0x7f3686ba2b60 = 0x7f3686ba2b78 {
                next = (nil)
                key = 0x7f3687f285e0
                value = 0x7f3686b9fb00
        }
        b[2] 0x7f3686ba2b68 = (nil)
        b[3] 0x7f3686ba2b70 = 0x7f3686b9a220 {
                next = (nil)
                key = 0x7f3687f2ade0
                value = 0x7f3686b9fc00
        }
]
----------------------------------------------------------
from: dmd_aaGetRvalue
this = 0x7f3686b95a20
nodes = 9
b_length = 32
[
        b[0] 0x7f3686b63000 = (nil)
        b[1] 0x7f3686b63008 = (nil)
        b[2] 0x7f3686b63010 = (nil)
        b[3] 0x7f3686b63018 = (nil)
        b[4] 0x7f3686b63020 = (nil)
        b[5] 0x7f3686b63028 = (nil)
        b[6] 0x7f3686b63030 = (nil)
        b[7] 0x7f3686b63038 = (nil)  <-- !!! Still null
        b[8] 0x7f3686b63040 = (nil)
        b[9] 0x7f3686b63048 = (nil)
        b[10] 0x7f3686b63050 = (nil)
        b[11] 0x7f3686b63058 = (nil)
        b[12] 0x7f3686b63060 = (nil)
        b[13] 0x7f3686b63068 = (nil)
        b[14] 0x7f3686b63070 = (nil)
        b[15] 0x7f3686b63078 = (nil)
        b[16] 0x7f3686b63080 = (nil)
        b[17] 0x7f3686b63088 = (nil)
        b[18] 0x7f3686b63090 = (nil)
        b[19] 0x7f3686b63098 = 0x7f3686b98ba0 {
                next = (nil)
                key = 0x7f3687f36000
                value = 0x7f3687f2c700
        }
        b[20] 0x7f3686b630a0 = 0x7f3686b95a58 {
                next = (nil)
                key = 0x7f3687f32fc0
                value = 0x7f3687f2c500
        }
        b[21] 0x7f3686b630a8 = 0x7f3686b98bc0 {
                next = (nil)
                key = 0x7f3687f36060
                value = 0x7f3687f37000
        }
        b[22] 0x7f3686b630b0 = 0x7f3686b98b80 {
                next = (nil)
                key = 0x7f3687f32fe0
                value = 0x7f3687f2c600
        }
        b[23] 0x7f3686b630b8 = 0x7f3686b98c00 {
                next = (nil)
                key = 0x7f3687f36040
                value = 0x7f3687f37330
        }
        b[24] 0x7f3686b630c0 = 0x7f3686b98c20 {
                next = (nil)
                key = 0x7f3687f360a0
                value = 0x7f3687f2c800
        }
        b[25] 0x7f3686b630c8 = (nil)
        b[26] 0x7f3686b630d0 = 0x7f3686b98be0 {
                next = (nil)
                key = 0x7f3687f36080
                value = 0x7f3687f34200
        }
        b[27] 0x7f3686b630d8 = (nil)
        b[28] 0x7f3686b630e0 = 0x7f3686b98c60 {
                next = (nil)
                key = 0x7f3687f360e0
                value = 0x7f3687f37990
        }
        b[29] 0x7f3686b630e8 = (nil)
        b[30] 0x7f3686b630f0 = 0x7f3686b98c40 {
                next = (nil)
                key = 0x7f3687f360c0
                value = 0x7f3687f37660
        }
        b[31] 0x7f3686b630f8 = (nil)
]
...
...
----------------------------------------------------------
from: dmd_aaGetRvalue
this = 0x7f3686b95a20
nodes = 9
b_length = 32
[
        b[0] 0x7f3686b63000 = (nil)
        b[1] 0x7f3686b63008 = (nil)
        b[2] 0x7f3686b63010 = (nil)
        b[3] 0x7f3686b63018 = (nil)
        b[4] 0x7f3686b63020 = (nil)
        b[5] 0x7f3686b63028 = (nil)
        b[6] 0x7f3686b63030 = (nil)
        b[7] 0x7f3686b63038 = 0x7f3686b9fb00 {  <-- !!! Now has value?!?!
                next = 0x559ae6f9b510
                key = 0x7f3687f285e0
                value = 0x7f3686b8c330
        }
        b[8] 0x7f3686b63040 = (nil)
        b[9] 0x7f3686b63048 = (nil)
        b[10] 0x7f3686b63050 = (nil)
        b[11] 0x7f3686b63058 = (nil)
        b[12] 0x7f3686b63060 = (nil)
        b[13] 0x7f3686b63068 = (nil)
        b[14] 0x7f3686b63070 = (nil)
        b[15] 0x7f3686b63078 = (nil)
        b[16] 0x7f3686b63080 = (nil)
        b[17] 0x7f3686b63088 = (nil)
        b[18] 0x7f3686b63090 = (nil)
        b[19] 0x7f3686b63098 = 0x7f3686b98ba0 {
                next = (nil)
                key = 0x7f3687f36000
                value = 0x7f3687f2c700
        }
        b[20] 0x7f3686b630a0 = 0x7f3686b95a58 {
                next = (nil)
                key = 0x7f3687f32fc0
                value = 0x7f3687f2c500
        }
        b[21] 0x7f3686b630a8 = 0x7f3686b98bc0 {
                next = (nil)
                key = 0x7f3687f36060
                value = 0x7f3687f37000
        }
        b[22] 0x7f3686b630b0 = 0x7f3686b98b80 {
                next = (nil)
                key = 0x7f3687f32fe0
                value = 0x7f3687f2c600
        }
        b[23] 0x7f3686b630b8 = 0x7f3686b98c00 {
                next = (nil)
                key = 0x7f3687f36040
                value = 0x7f3687f37330
        }
        b[24] 0x7f3686b630c0 = 0x7f3686b98c20 {
                next = (nil)
                key = 0x7f3687f360a0
                value = 0x7f3687f2c800
        }
        b[25] 0x7f3686b630c8 = (nil)
        b[26] 0x7f3686b630d0 = 0x7f3686b98be0 {
                next = (nil)
                key = 0x7f3687f36080
                value = 0x7f3687f34200
        }
        b[27] 0x7f3686b630d8 = (nil)
        b[28] 0x7f3686b630e0 = 0x7f3686b98c60 {
                next = (nil)
                key = 0x7f3687f360e0
                value = 0x7f3687f37990
        }
        b[29] 0x7f3686b630e8 = (nil)
        b[30] 0x7f3686b630f0 = 0x7f3686b98c40 {
                next = (nil)
                key = 0x7f3687f360c0
                value = 0x7f3687f37660
        }
        b[31] 0x7f3686b630f8 = (nil)
]
Segmentation fault (core dumped)
fail

--