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digitalmars.D - Clarification on testsuite 'runnable/testmath.d'

reply Daniel Green <venix1 gmail.com> writes:
I've been working on fixing GDC/MinGW's runtime support.  I ran across 
the following and was hoping to get a clarification on what DMD does 
differently than GDC.

void testexp()
{
     printf("exp(3.0) = %Lg, %Lg\n", exp(3.0), E * E * E);
     assert(equals(exp(3.0), E * E * E, 16));
}

Of interest is exp(3.0).  GDC matches exp(3.0) to double exp(double). 
This causes problems with printf due to %Lg wanting a real but only 
receiving a double.

Looking at the D specification for overloading functions.
     1. no match
     2. match with implicit conversions
     3. match with conversion to const
     4. exact match


The specification doesn't indicate what levels are better.  I would 
guess 4 is the best since an exact match should take precedence.
However, that results in GDC matching exp(3.0) to double exp(double).

How does DMD match exp(3.0)?

Could it possibly be a typo?  For 32-bit this test passes because the 
printf doesn't segfault, it's only  noticeable with 64-bit since it 
segfaults.
Jan 13 2012
next sibling parent reply Walter Bright <newshound2 digitalmars.com> writes:
On 1/13/2012 10:51 PM, Daniel Green wrote:

 Could it possibly be a typo? For 32-bit this test passes because the printf
 doesn't segfault, it's only noticeable with 64-bit since it segfaults.


3.0 should match double, when there is both double and real.
Jan 14 2012
parent reply Daniel Green <venix1 gmail.com> writes:
On 1/14/2012 3:29 AM, Walter Bright wrote:

 On 1/13/2012 10:51 PM, Daniel Green wrote:

 Could it possibly be a typo? For 32-bit this test passes because the
 printf
 doesn't segfault, it's only noticeable with 64-bit since it segfaults.


 3.0 should match double, when there is both double and real.


On 1/14/2012 3:29 AM, Walter Bright wrote:

 On 1/13/2012 10:51 PM, Daniel Green wrote:

 Could it possibly be a typo? For 32-bit this test passes because the
 printf
 doesn't segfault, it's only noticeable with 64-bit since it segfaults.


 3.0 should match double, when there is both double and real.


When I run the following through DMD r is type real.  For GDC r is type 
double.

The matched function would be
    double exp(double x)  safe pure nothrow  { return exp(cast(real)x); }.

Is it expected that DMD promotes a double to real?


// GDC: r is type double
// DMD: r is type real
import std.stdio;
import std.math;

void main()
{
     auto r = exp(3.0);
     writefln("%s", typeof(r).stringof);
}
Jan 14 2012
parent reply Iain Buclaw <ibuclaw ubuntu.com> writes:
On 14 January 2012 15:20, Daniel Green <venix1 gmail.com> wrote:

 On 1/14/2012 3:29 AM, Walter Bright wrote:

 On 1/13/2012 10:51 PM, Daniel Green wrote:

 Could it possibly be a typo? For 32-bit this test passes because the
 printf
 doesn't segfault, it's only noticeable with 64-bit since it segfaults.



 3.0 should match double, when there is both double and real.



 On 1/14/2012 3:29 AM, Walter Bright wrote:

 On 1/13/2012 10:51 PM, Daniel Green wrote:

 Could it possibly be a typo? For 32-bit this test passes because the
 printf
 doesn't segfault, it's only noticeable with 64-bit since it segfaults.


 3.0 should match double, when there is both double and real.


 When I run the following through DMD r is type real. =A0For GDC r is type
 double.

 The matched function would be
 =A0 double exp(double x)  safe pure nothrow =A0{ return exp(cast(real)x);=


 }.

 Is it expected that DMD promotes a double to real?


 // GDC: r is type double
 // DMD: r is type real
 import std.stdio;
 import std.math;

 void main()
 {
 =A0 =A0auto r =3D exp(3.0);
 =A0 =A0writefln("%s", typeof(r).stringof);
 }


Strange, I get 'double' for both DMD and GDC... is this maybe a Windows thi=
ng?


--=20
Iain Buclaw

*(p < e ? p++ : p) =3D (c & 0x0f) + '0';
Jan 14 2012
parent Daniel Green <venix1 gmail.com> writes:
On 1/14/2012 10:34 AM, Iain Buclaw wrote:

 Strange, I get 'double' for both DMD and GDC... is this maybe a Windows thing?


Just ran it with linux and got 'double' as well.  So it appears to be a 
Windows thing.
Jan 14 2012
prev sibling parent Iain Buclaw <ibuclaw ubuntu.com> writes:
I think the only difference may be that gdc possibly folds the call to
exp().

Check the difference between what code gdc generates compared to how gcc
processed it:  -fdump-tree-original  -fdump-tree-optimized

----
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';

On 14 Jan 2012 06:56, "Daniel Green" <venix1 gmail.com> wrote:

 I've been working on fixing GDC/MinGW's runtime support.  I ran across


the following and was hoping to get a clarification on what DMD does
differently than GDC.

 void testexp()
 {
    printf("exp(3.0) = %Lg, %Lg\n", exp(3.0), E * E * E);
    assert(equals(exp(3.0), E * E * E, 16));
 }

 Of interest is exp(3.0).  GDC matches exp(3.0) to double exp(double).


This causes problems with printf due to %Lg wanting a real but only
receiving a double.

 Looking at the D specification for overloading functions.
    1. no match
    2. match with implicit conversions
    3. match with conversion to const
    4. exact match


 The specification doesn't indicate what levels are better.  I would guess


4 is the best since an exact match should take precedence.

 However, that results in GDC matching exp(3.0) to double exp(double).

 How does DMD match exp(3.0)?

 Could it possibly be a typo?  For 32-bit this test passes because the


printf doesn't segfault, it's only  noticeable with 64-bit since it
segfaults.
Jan 14 2012