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digitalmars.D.learn - Why do ints defined in template mixins have garbage values?

reply Johannes Riecken <johannes.riecken gmail.com> writes:
Code:

import std.conv;
import std.stdio;

mixin template genInts()
{
   enum arr = [0,1];
   static foreach (t; arr) {
     mixin("int i" ~ to!string(t) ~ " = 5;");
   }
}

void main() {
   mixin genInts!();
   writeln(i0);
   writeln(i1);
}


Expected output:
5
5

Actual output is two garbage integer values.
Dec 11 2018
next sibling parent reply Steven Schveighoffer <schveiguy gmail.com> writes:
On 12/11/18 4:09 PM, Johannes Riecken wrote:

 Code:
 
 import std.conv;
 import std.stdio;
 
 mixin template genInts()
 {
    enum arr = [0,1];
    static foreach (t; arr) {
      mixin("int i" ~ to!string(t) ~ " = 5;");
    }
 }
 
 void main() {
    mixin genInts!();
    writeln(i0);
    writeln(i1);
 }
 
 
 Expected output:
 5
 5
 
 Actual output is two garbage integer values.


Looks like a bug to me in static foreach.

Using -vcg-ast, it appears that the int definitions do not show up in main.

If I add an int using a regular declaration or a straight mixin("int i0 
= 5;"); then the variable shows up.

-Steve
Dec 11 2018
parent reply Kagamin <spam here.lot> writes:
On Tuesday, 11 December 2018 at 21:19:59 UTC, Steven 
Schveighoffer wrote:

 If I add an int using a regular declaration or a straight 
 mixin("int i0 = 5;"); then the variable shows up.


mixin template genInts()
{
     enum arr = [0];
     static foreach (t; arr)
     {
         mixin("int i0 = 5;");
     }
}

Still prints garbage.
Dec 12 2018
parent Steven Schveighoffer <schveiguy gmail.com> writes:
On 12/12/18 10:22 AM, Kagamin wrote:

 On Tuesday, 11 December 2018 at 21:19:59 UTC, Steven Schveighoffer wrote:

 If I add an int using a regular declaration or a straight mixin("int 
 i0 = 5;"); then the variable shows up.


 
 mixin template genInts()
 {
      enum arr = [0];
      static foreach (t; arr)
      {
          mixin("int i0 = 5;");
      }
 }
 
 Still prints garbage.


I meant this:

mixin template genInts()
{
    mixin("int i0 = 5;");
}

It's still a static foreach + mixin + mixin template bug, all those are 
needed to make it fail.

What's interesting is that dmd thinks there is an i0 (there is no error 
on a missing symbol), but the ast printed doesn't show a declaration for it.

-Steve
Dec 12 2018
prev sibling next sibling parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Tue, Dec 11, 2018 at 09:09:55PM +0000, Johannes Riecken via
Digitalmars-d-learn wrote:

 Code:
 
 import std.conv;
 import std.stdio;
 
 mixin template genInts()
 {
   enum arr = [0,1];
   static foreach (t; arr) {
     mixin("int i" ~ to!string(t) ~ " = 5;");
   }
 }
 
 void main() {
   mixin genInts!();
   writeln(i0);
   writeln(i1);
 }
 
 
 Expected output:
 5
 5
 
 Actual output is two garbage integer values.


Whoa.  That looks like a compiler bug. File a bug here:

	https://issues.dlang.org/enter_bug.cgi


T

-- 
There are two ways to write error-free programs; only the third one works.
Dec 11 2018
parent reply AlCaponeJr <a c.com> writes:
On Tuesday, 11 December 2018 at 21:17:46 UTC, H. S. Teoh wrote:

 Whoa.  That looks like a compiler bug. File a bug here:
 ...


Genuinely asking if this is a case of lacking of unit test for 
the Compiler or this is a case that where is hard to test or 
prevent?

Al.
Dec 12 2018
parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Wed, Dec 12, 2018 at 01:35:00PM +0000, AlCaponeJr via Digitalmars-d-learn
wrote:

 On Tuesday, 11 December 2018 at 21:17:46 UTC, H. S. Teoh wrote:

 Whoa.  That looks like a compiler bug. File a bug here:
 ...


 
 Genuinely asking if this is a case of lacking of unit test for the
 Compiler or this is a case that where is hard to test or prevent?


[...]

I think it's just a case of too many possible combinations of features
to test that some inevitably get overlooked.  Combinatorial explosion.
But once bug reports like these are filed and fixed, more unittests will
be added, which increase the surface area of tested feature combinations
and (hopefully) reduce the likelihood of similar bugs.


T

-- 
Talk is cheap. Whining is actually free. -- Lars Wirzenius
Dec 12 2018
parent Michelle Long <HappyDance321 gmail.com> writes:
On Wednesday, 12 December 2018 at 16:33:02 UTC, H. S. Teoh wrote:

 On Wed, Dec 12, 2018 at 01:35:00PM +0000, AlCaponeJr via 
 Digitalmars-d-learn wrote:

 On Tuesday, 11 December 2018 at 21:17:46 UTC, H. S. Teoh wrote:

 Whoa.  That looks like a compiler bug. File a bug here:
 ...


 
 Genuinely asking if this is a case of lacking of unit test for 
 the Compiler or this is a case that where is hard to test or 
 prevent?


 [...]

 I think it's just a case of too many possible combinations of 
 features to test that some inevitably get overlooked.  
 Combinatorial explosion. But once bug reports like these are 
 filed and fixed, more unittests will be added, which increase 
 the surface area of tested feature combinations and (hopefully) 
 reduce the likelihood of similar bugs.


Proper factorization prevents this. It may be a difficult problem 
but all it requires is to think before one leaps. People have 
already developed randomized program testing(essentially 
generates random but working programs(or non-working for error 
codes)).  Someone could setup a machine that continuously 
generates these programs and tests the compiler. Any 
discrepancies are reported and investigated.
Dec 12 2018
prev sibling next sibling parent "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
P.S.  Just looked at the disassembly.  Seems to be a codegen bug -- the
code appears to be trying to lookup local variables (presumably i0 and
i1), but somehow the initialization code is missing.


--T

On Tue, Dec 11, 2018 at 09:09:55PM +0000, Johannes Riecken via
Digitalmars-d-learn wrote:

 Code:
 
 import std.conv;
 import std.stdio;
 
 mixin template genInts()
 {
   enum arr = [0,1];
   static foreach (t; arr) {
     mixin("int i" ~ to!string(t) ~ " = 5;");
   }
 }
 
 void main() {
   mixin genInts!();
   writeln(i0);
   writeln(i1);
 }
 
 
 Expected output:
 5
 5
 
 Actual output is two garbage integer values.


-- 
"If you're arguing, you're losing." -- Mike Thomas
Dec 11 2018
prev sibling parent Johannes Loher <johannes.loher fg4f.de> writes:
On Tuesday, 11 December 2018 at 21:09:55 UTC, Johannes Riecken 
wrote:

 Code:

 import std.conv;
 import std.stdio;

 mixin template genInts()
 {
   enum arr = [0,1];
   static foreach (t; arr) {
     mixin("int i" ~ to!string(t) ~ " = 5;");
   }
 }

 void main() {
   mixin genInts!();
   writeln(i0);
   writeln(i1);
 }


 Expected output:
 5
 5

 Actual output is two garbage integer values.


Definitely a compiler bug.

According to 
https://run.dlang.io/gist/1e6e7574a8762d7fed5a3aa22390493d?compiler=dreg
Garbage values are printed since 2.078.1.

compiling with ldc results in a segmentation fault when running 
the program: 
https://run.dlang.io/gist/02780bfe33a2bfd000aa5718a3fe6505?compiler=ldc
Dec 12 2018