digitalmars.D.learn - issue with each specifically for x86

Matt Gamble (36/36) Mar 07 2018 This is a record for me with two 32bit vs 64bit issues in one

=?UTF-8?Q?Ali_=c3=87ehreli?= (14/59) Mar 07 2018 Confirmed on Linux with dmd 2.078.1
Steven Schveighoffer (16/61) Mar 07 2018 It has something to do with the fact that you are returning the value:

ag0aep6g (17/30) Mar 07 2018 It's beautiful:

Steven Schveighoffer (3/25) Mar 07 2018 Are all those calls required? That's one crazy bug.
ag0aep6g (2/19) Mar 07 2018 With `real` instead of `double` x86_64 is also affected.

ketmar (3/20) Mar 07 2018 yeah. that is 'cause SSE cannot do math with 80-bit floats, and compiler...
Matt Gamble (6/25) Mar 07 2018 Wow. Good to know I'm not crazy. I was afk for a bit, sorry. I

ketmar (3/27) Mar 07 2018 sure, it is still there in git HEAD. it is not the bug that can be fixed...

Matt Gamble (5/19) Mar 07 2018 Ok, this has been submitted as a bug.

ketmar (2/4) Mar 07 2018 thank you.

ketmar (9/9) Mar 07 2018 Steven Schveighoffer wrote:

H. S. Teoh (6/14) Mar 07 2018 Nice catch! Is there a bug filed for this yet? If not, it should be.

ketmar (3/13) Mar 07 2018 it seems that no bug is filled yet. feel free to do so. ;-) or maybe OP
ketmar (7/17) Mar 07 2018 btw, this is specific to `cast(void)`. if you'll remove the cast, or do

Matt Gamble <gamblemj gmail.com> writes:

This is a record for me with two 32bit vs 64bit issues in one 
day. Seems to be a problem with using "each" under 32bit which 
can be fixed by using foreach or switching to x64. Am I doing 
something wrong or is this the second bug I've found today?

Below is a silly case, that replicates an error. (i.e. I know I 
could use iota(0,9,2).array), but that does not demonstrate the 
potential bug and would not fix my actual program.)

import std.range;
import std.algorithm;
import std.stdio;

unittest
{
	auto a = new double[9];
	a[0] = 0;
	iota(1,a.length).each!(i => a[i] = a[i-1] + 2);
	writeln(a);
}

//x86, wrong, error
//[-nan, 2, 4, 6, 8, 10, 12, 14, 16]
//First-chance exception: std.format.FormatException Unterminated 
format specifier: "%" at 
C:\D\dmd2\windows\bin\..\..\src\phobos\std\format.d(1175)

//x64, correct
//[0, 2, 4, 6, 8, 10, 12, 14, 16]

unittest
{
	auto a = new double[9];
	a[0] = 0;
	foreach(i; 1..a.length) a[i] = a[i - 1] + 2;
	writeln(a);
}

//x86, correct
//[0, 2, 4, 6, 8, 10, 12, 14, 16]

//x64, correct
//[0, 2, 4, 6, 8, 10, 12, 14, 16]

This is windows 10, DMD v2.076.1

Mar 07 2018

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 03/07/2018 10:57 AM, Matt Gamble wrote:
 This is a record for me with two 32bit vs 64bit issues in one day. Seems 
 to be a problem with using "each" under 32bit which can be fixed by 
 using foreach or switching to x64. Am I doing something wrong or is this 
 the second bug I've found today?
 
 Below is a silly case, that replicates an error. (i.e. I know I could 
 use iota(0,9,2).array), but that does not demonstrate the potential bug 
 and would not fix my actual program.)
 
 import std.range;
 import std.algorithm;
 import std.stdio;
 
 unittest
 {
      auto a = new double[9];
      a[0] = 0;
      iota(1,a.length).each!(i => a[i] = a[i-1] + 2);
      writeln(a);
 }
 
 //x86, wrong, error
 //[-nan, 2, 4, 6, 8, 10, 12, 14, 16]
 //First-chance exception: std.format.FormatException Unterminated format 
 specifier: "%" at C:\D\dmd2\windows\bin\..\..\src\phobos\std\format.d(1175)
 
 //x64, correct
 //[0, 2, 4, 6, 8, 10, 12, 14, 16]
 
 unittest
 {
      auto a = new double[9];
      a[0] = 0;
      foreach(i; 1..a.length) a[i] = a[i - 1] + 2;
      writeln(a);
 }
 
 //x86, correct
 //[0, 2, 4, 6, 8, 10, 12, 14, 16]
 
 //x64, correct
 //[0, 2, 4, 6, 8, 10, 12, 14, 16]
 
 This is windows 10, DMD v2.076.1
 

Confirmed on Linux with dmd 2.078.1

It's somehow related to the unused return value of the lambda. The 
following code has the same error:

     iota(1,a.length).each!((i) {
             a[i] = a[i-1] + 2;
             return a[i];
         });

The error disappears when that return statement is commented-out.

Please file a dmd bug after making sure that 2.079 still has it. (Too 
lazy to install right now.)

An ldc that I have handy does not have this bug:

   based on DMD v2.073.2 and LLVM 4.0.0

Ali

Mar 07 2018

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 3/7/18 1:57 PM, Matt Gamble wrote:
 This is a record for me with two 32bit vs 64bit issues in one day. Seems 
 to be a problem with using "each" under 32bit which can be fixed by 
 using foreach or switching to x64. Am I doing something wrong or is this 
 the second bug I've found today?
 
 Below is a silly case, that replicates an error. (i.e. I know I could 
 use iota(0,9,2).array), but that does not demonstrate the potential bug 
 and would not fix my actual program.)
 
 import std.range;
 import std.algorithm;
 import std.stdio;
 
 unittest
 {
      auto a = new double[9];
      a[0] = 0;
      iota(1,a.length).each!(i => a[i] = a[i-1] + 2);
      writeln(a);
 }
 
 //x86, wrong, error
 //[-nan, 2, 4, 6, 8, 10, 12, 14, 16]
 //First-chance exception: std.format.FormatException Unterminated format 
 specifier: "%" at C:\D\dmd2\windows\bin\..\..\src\phobos\std\format.d(1175)
 
 //x64, correct
 //[0, 2, 4, 6, 8, 10, 12, 14, 16]
 
 unittest
 {
      auto a = new double[9];
      a[0] = 0;
      foreach(i; 1..a.length) a[i] = a[i - 1] + 2;
      writeln(a);
 }
 
 //x86, correct
 //[0, 2, 4, 6, 8, 10, 12, 14, 16]
 
 //x64, correct
 //[0, 2, 4, 6, 8, 10, 12, 14, 16]
 
 This is windows 10, DMD v2.076.1
 

It has something to do with the fact that you are returning the value:

iota(1, a.length).each!((i) {a[i] = a[i - 1] + 2;}); // ok
iota(1, a.length).each!((i) {return a[i] = a[i - 1] + 2;}); // shows error


Which is odd to say the least, I don't think each is supposed to do 
anything with the return value.

I don't get the exception BTW (2.078.1 Windows 10).

Looking at each, it looks like it does this:

cast(void) unaryFun!pred(r.front);

So I tried this:

auto pred = i => a[i] = a[i-1] + 2;
foreach(i; 1 .. a.length)
    cast(void)pred(i);

And I see the -nan value. Remove the cast(void) and I don't see it.

Clearly there is some codegen issue here.

-Steve

Mar 07 2018

ag0aep6g <anonymous example.com> writes:

On 03/07/2018 08:54 PM, Steven Schveighoffer wrote:
 Looking at each, it looks like it does this:
 
 cast(void) unaryFun!pred(r.front);
 
 So I tried this:
 
 auto pred = i => a[i] = a[i-1] + 2;
 foreach(i; 1 .. a.length)
     cast(void)pred(i);
 
 And I see the -nan value. Remove the cast(void) and I don't see it.
 
 Clearly there is some codegen issue here.

It's beautiful:

----
double f() { return 1; }

void main()
{
     cast(void) f();
     cast(void) f();
     cast(void) f();
     cast(void) f();
     cast(void) f();
     cast(void) f();
     cast(void) f();

     double b = 2;
     assert(b == 2); /* fails; should pass */
}
----

Mar 07 2018

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 3/7/18 3:09 PM, ag0aep6g wrote:
 On 03/07/2018 08:54 PM, Steven Schveighoffer wrote:
 Clearly there is some codegen issue here.

 
 It's beautiful:
 
 ----
 double f() { return 1; }
 
 void main()
 {
      cast(void) f();
      cast(void) f();
      cast(void) f();
      cast(void) f();
      cast(void) f();
      cast(void) f();
      cast(void) f();
 
      double b = 2;
      assert(b == 2); /* fails; should pass */
 }
 ----

Are all those calls required? That's one crazy bug.

-Steve

Mar 07 2018

ag0aep6g <anonymous example.com> writes:

On 03/07/2018 09:09 PM, ag0aep6g wrote:
 ----
 double f() { return 1; }
 
 void main()
 {
      cast(void) f();
      cast(void) f();
      cast(void) f();
      cast(void) f();
      cast(void) f();
      cast(void) f();
      cast(void) f();
 
      double b = 2;
      assert(b == 2); /* fails; should pass */
 }
 ----

With `real` instead of `double` x86_64 is also affected.

Mar 07 2018