http://d.puremagic.com/bugzilla/show_bug.cgi?id=72

           Summary: valgrind: use of unitialized values in the gcx module
           Product: D
           Version: 0.150
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: thomas-dloop@kuehne.cn


Context:
DStress' next torture step will include running new compiler versions,
generated programs and old compiler version with changed/new test cases under
valgrind. The aim is to locate usage of uninitialized values and potential GC
issues.

See also:
dkdk2l$76$1@digitaldaemon.com: Tiago Gasiba's "memory leakage in D"
djtk1c$22gs$1@digitaldaemon.com: Tiago Gasiba's "Garbage Collector Bug?"

Potentially related:
dv416n$2s5q$1@digitaldaemon.com: Johan Gröngvist's "A program leaking memory."

The snipplets below are missing line numbers due to Phobos compilation settings
and a not yet triangled "@@ parsing :(0,7) gave NULL type ((0,7) remains)"
valgrind issue.

Conditional jump or move depends on uninitialized value(s)
   at 0x80665A2: _D3gcx3Gcx8findPoolFPvZPS3gcx4Pool (in /tmp/dstress/log)
   by 0x80669CF: _D3gcx3Gcx4markFPvPvZv (in /tmp/dstress/log)
   by 0x8066BB7: _D3gcx3Gcx11fullcollectFPvZk (in /tmp/dstress/log)
   by 0x8066A79: _D3gcx3Gcx16fullcollectshellFZk (in /tmp/dstress/log)
   by 0x8065BAF: _D3gcx2GC12mallocNoSyncFkZPv (in /tmp/dstress/log)
   by 0x8065AF6: _D3gcx2GC6mallocFkZPv (in /tmp/dstress/log)
   by 0x806000D: _d_arrayappendc (in /tmp/dstress/log)

Use of uninitialised value of size 4
   at 0x80669E3: _D3gcx3Gcx4markFPvPvZv (in /tmp/dstress/log)
   by 0x8066BB7: _D3gcx3Gcx11fullcollectFPvZk (in /tmp/dstress/log)
   by 0x8066A79: _D3gcx3Gcx16fullcollectshellFZk (in /tmp/dstress/log)
   by 0x8065BAF: _D3gcx2GC12mallocNoSyncFkZPv (in /tmp/dstress/log)
   by 0x8065AF6: _D3gcx2GC6mallocFkZPv (in /tmp/dstress/log)
   by 0x806000D: _d_arrayappendc (in /tmp/dstress/log)

Use of uninitialised value of size 4
   at 0x8067358: _D6gcbits6GCBits4testFkZk (in /tmp/dstress/log)
   by 0x8066A17: _D3gcx3Gcx4markFPvPvZv (in /tmp/dstress/log)
   by 0x8066BB7: _D3gcx3Gcx11fullcollectFPvZk (in /tmp/dstress/log)
   by 0x8066A79: _D3gcx3Gcx16fullcollectshellFZk (in /tmp/dstress/log)
   by 0x8065BAF: _D3gcx2GC12mallocNoSyncFkZPv (in /tmp/dstress/log)
   by 0x8065AF6: _D3gcx2GC6mallocFkZPv (in /tmp/dstress/log)
   by 0x806000D: _d_arrayappendc (in /tmp/dstress/log)

Use of uninitialised value of size 4
   at 0x8067370: _D6gcbits6GCBits3setFkZv (in /tmp/dstress/log)
   by 0x8066A24: _D3gcx3Gcx4markFPvPvZv (in /tmp/dstress/log)
   by 0x8066BB7: _D3gcx3Gcx11fullcollectFPvZk (in /tmp/dstress/log)
   by 0x8066A79: _D3gcx3Gcx16fullcollectshellFZk (in /tmp/dstress/log)
   by 0x8065BAF: _D3gcx2GC12mallocNoSyncFkZPv (in /tmp/dstress/log)
   by 0x8065AF6: _D3gcx2GC6mallocFkZPv (in /tmp/dstress/log)
   by 0x806000D: _d_arrayappendc (in /tmp/dstress/log)

Conditional jump or move depends on uninitialised value(s)
   at 0x8066C6A: _D3gcx3Gcx11fullcollectFPvZk (in /tmp/dstress/log)
   by 0x8066A79: _D3gcx3Gcx16fullcollectshellFZk (in /tmp/dstress/log)
   by 0x8065BAF: _D3gcx2GC12mallocNoSyncFkZPv (in /tmp/dstress/log)
   by 0x8065AF6: _D3gcx2GC6mallocFkZPv (in /tmp/dstress/log)
   by 0x806000D: _d_arrayappendc (in /tmp/dstress/log)


-- 

<d-bugmail@puremagic.com> wrote in message news:bug-72-3@http.d.puremagic.com/bugzilla/...
> Use of uninitialised value of size 4
>   at 0x8067370: _D6gcbits6GCBits3setFkZv (in /tmp/dstress/log)
>   by 0x8066A24: _D3gcx3Gcx4markFPvPvZv (in /tmp/dstress/log)
>   by 0x8066BB7: _D3gcx3Gcx11fullcollectFPvZk (in /tmp/dstress/log)
>   by 0x8066A79: _D3gcx3Gcx16fullcollectshellFZk (in /tmp/dstress/log)
>   by 0x8065BAF: _D3gcx2GC12mallocNoSyncFkZPv (in /tmp/dstress/log)
>   by 0x8065AF6: _D3gcx2GC6mallocFkZPv (in /tmp/dstress/log)
>   by 0x806000D: _d_arrayappendc (in /tmp/dstress/log)

I don't know what to make of this. Here's the code in question:

void set(uint i)
in
{
    assert(i < nbits);
}
body
{
    //(cast(bit *)(data + 1))[i] = 1;
    data[1 + (i >> BITS_SHIFT)] |= (1 << (i & BITS_MASK));
}

Where's the use of an uninitialized value?

Walter Bright schrieb am 2006-03-25:
>
><d-bugmail@puremagic.com> wrote in message
> news:bug-72-3@http.d.puremagic.com/bugzilla/...
>> Use of uninitialised value of size 4
>>   at 0x8067370: _D6gcbits6GCBits3setFkZv (in /tmp/dstress/log)
>>   by 0x8066A24: _D3gcx3Gcx4markFPvPvZv (in /tmp/dstress/log)
>>   by 0x8066BB7: _D3gcx3Gcx11fullcollectFPvZk (in /tmp/dstress/log)
>>   by 0x8066A79: _D3gcx3Gcx16fullcollectshellFZk (in /tmp/dstress/log)
>>   by 0x8065BAF: _D3gcx2GC12mallocNoSyncFkZPv (in /tmp/dstress/log)
>>   by 0x8065AF6: _D3gcx2GC6mallocFkZPv (in /tmp/dstress/log)
>>   by 0x806000D: _d_arrayappendc (in /tmp/dstress/log)
>
> I don't know what to make of this. Here's the code in question:
>
> void set(uint i)
> in
> {
>     assert(i < nbits);
> }
> body
> {
>     //(cast(bit *)(data + 1))[i] = 1;
>     data[1 + (i >> BITS_SHIFT)] |= (1 << (i & BITS_MASK));
> }
>
> Where's the use of an uninitialized value?

Seems to be a side effect of the "-release" flag.

compiling phobos with no flags:
=> no uninitialized value messages

compiling phobos with "-inline":
=> no uninitialized value messages

compiling phobos with "-O":
=> no unitialized value messages

compiling phobos with "-release":
=> "_D6gcbits6GCBits3setFkZv" message twice

compiling phobos with "-inline -O":
=> no unitialized value messages

compiling phobos with "-inline -release":
=> "_D6gcbits6GCBits3setFkZv" message twice

compiling phobos with "-O -release":
=> "_D6gcbits6GCBits3setFkZv" message twice

compiling phobos with "-inline -O -release":
=> "_D6gcbits6GCBits3setFkZv" message twice

Thomas

Which file(s) in phobos triggers this?  I'll create a minimalized test case.

Brad Roberts schrieb am 2006-03-25:
> Which file(s) in phobos triggers this?  I'll create a minimalized test case.

The code below triggers the _D6gcbits6GCBits3setFkZv issue.

Phobos compiled without "-release":
2 x Conditional jump or move depends on uninitialised value
2 x Use of uninitialised value of size 4

Phobos compiled with "-release":
2 x Use of uninitialised value of size 4

> int main(){
>	char[] dummy;
>	dummy = "abc".dup;
>	for(int a=0; a < 120; a++){
>		char[] tmp = new char[a % 80];
>		for(int b=0; b  < a % 10; b++){
>			dummy = dummy[0 .. $ % 33] ~ tmp[0 .. $ % 11] ~ dummy[ $ % 33 .. $];
>		}
>	}
>	return dummy.length / 2000002;
> }

Setting: DMD-0.150 / Linux / Valgrind-3.1.1

Thomas