https://d.puremagic.com/issues/show_bug.cgi?id=11553

           Summary: dmd segfault with recursive template
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: john.loughran.colvin@gmail.com


--- Comment #0 from John Colvin <john.loughran.colvin@gmail.com> 2013-11-19 12:39:23 GMT ---
An example that is clearly wrong code, but segfaults the compiler on Scope::push

template A(alias T)
{
    template A()
    {
    alias A = T!();
    }
}
alias B() = A!(.B);

static if(A!B){}


I have similar but correct code that triggers the same fault, I'll add it when I've minimised it properly.

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--- Comment #1 from John Colvin <john.loughran.colvin@gmail.com> 2013-11-19 13:45:55 GMT ---
Ok this is proving near impossible to reduce. Changing the slightest things moves the segfault to different parts of the compiler and it's very hard to find examples that are correct and fail. I've seen

Scope::Scope(Scope*),

functionResolve(Match*, Dsymbol*, Loc, Scope*, Array<RootObject>*, Type*,
Array<Expression>*)::ParamDeduce::fp(TemplateDeclaration*),

TemplateInstance::findBestMatch(Scope*, Array<Expression>*) (),

TemplateTupleParameter::matchArg(Loc, Scope*, Array<RootObject>*, unsigned
long, Array<TemplateParameter>*, Array<RootObject>*, Declaration**) (),

Dsymbol::Dsymbol()

so far, if that's of any help at all.

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yebblies <yebblies@gmail.com> changed:

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


--- Comment #2 from yebblies <yebblies@gmail.com> 2013-11-20 01:07:34 EST ---
(In reply to comment #1)
> Ok this is proving near impossible to reduce. Changing the slightest things moves the segfault to different parts of the compiler and it's very hard to find examples that are correct and fail. I've seen
> 
> Scope::Scope(Scope*),
> 
> functionResolve(Match*, Dsymbol*, Loc, Scope*, Array<RootObject>*, Type*,
> Array<Expression>*)::ParamDeduce::fp(TemplateDeclaration*),
> 
> TemplateInstance::findBestMatch(Scope*, Array<Expression>*) (),
> 
> TemplateTupleParameter::matchArg(Loc, Scope*, Array<RootObject>*, unsigned
> long, Array<TemplateParameter>*, Array<RootObject>*, Declaration**) (),
> 
> Dsymbol::Dsymbol()
> 
> so far, if that's of any help at all.

It's jumping around because the segfault is a stack overflow.  Chances are any segfault you see will be the same thing underneath.

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--- Comment #3 from John Colvin <john.loughran.colvin@gmail.com> 2013-11-19 14:42:42 GMT ---
Finally, a correct (should compile) example that causes a segfault. It's still
a little large, sorry:

struct Pack(T ...)
{
    alias Unpack = T;
    enum length = T.length;
}

template isPack(TList ...)
{
    static if(TList.length == 1 &&
          is(Pack!(TList[0].Unpack) == TList[0]))
    {
    enum isPack = true;
    }
    else
    {
    enum isPack = false;
    }
}

template PartialApply(alias T, uint argLoc, Arg ...)
    if(Arg.length == 1)
{
    template PartialApply(L ...)
    {
    alias PartialApply = T!(L[0 .. argLoc], Arg, L[argLoc .. $]);
    }
}

template _hasLength(size_t len, T)
{
    static if(T.length == len)
    {
    enum _hasLength = true;
    }
    else
    {
    enum _hasLength = false;
    }
}

alias _hasLength(size_t len) = PartialApply!(._hasLength, 0, len);


alias hl1 = _hasLength!1;

//this segfaults
static if(!isPack!hl1){ pragma(msg, "All good 1"); }

//these are fine
static if(hl1!(Pack!(5))) { pragma(msg, "All good 2"); }

static if(!hl1!(Pack!())) { pragma(msg, "All good 3"); }


The result:
Program received signal SIGSEGV, Segmentation fault.
0x0000000000434a45 in Dsymbol::Dsymbol(Identifier*) ()

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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice, pull


--- Comment #4 from Kenji Hara <k.hara.pg@gmail.com> 2013-11-19 07:48:46 PST ---
https://github.com/D-Programming-Language/dmd/pull/2826

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--- Comment #5 from John Colvin <john.loughran.colvin@gmail.com> 2013-11-19 16:24:25 GMT ---
Thanks Kenji, that fixes the problem in my full code-base too.

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--- Comment #6 from github-bugzilla@puremagic.com 2014-01-05 12:27:15 PST ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/fcd656147f10ec53f68df473883ddc68aaee546e fix Issue 11553 - dmd segfault with recursive template

https://github.com/D-Programming-Language/dmd/commit/a78295a1c99299880c8c8adb475688d1e1ae8484 Merge pull request #2826 from 9rnsr/fix11553

Issue 11553 - dmd segfault with recursive template

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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|major                       |regression


--- Comment #7 from Kenji Hara <k.hara.pg@gmail.com> 2014-01-07 02:31:10 PST ---
(In reply to comment #0)
> An example that is clearly wrong code, but segfaults the compiler on Scope::push
> 
> template A(alias T)
> {
>     template A()
>     {
>     alias A = T!();
>     }
> }
> alias B() = A!(.B);
> 
> static if(A!B){}

With 2.063, following equivalent code did not cause segfault.

template A(alias T)
{
    template A()
    {
        alias A = T!();
    }
}
template B() { alias B = A!(.B); }
static if (A!B) {}  // Line 9

Output:
test.d(9): Error: expression template A() of type void does not have a boolean
value

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--- Comment #8 from github-bugzilla@puremagic.com 2014-01-07 02:33:10 PST ---
Commit pushed to 2.065 at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/e1866902b88e36537197da16b098afd2df304425 Merge pull request #2826 from 9rnsr/fix11553

Issue 11553 - dmd segfault with recursive template

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