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digitalmars.D.bugs - [Issue 9904] New: typeof(null) can be casted to aggregate type if .sizeof equals size of pointer

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9904

           Summary: typeof(null) can be casted to aggregate type if
                    .sizeof equals size of pointer
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: andrej.mitrovich gmail.com



07:42:22 PDT ---
struct S1
{
    int x;
}

struct S2
{
    int x;
    byte b;
}

void main()
{
    static assert(S1.sizeof == typeof(null).sizeof);
    auto s1 = cast(S1)null;  // compiles, should not

    static assert(S2.sizeof != typeof(null).sizeof);
    auto s2 = cast(S2)null;  // NG, as it should
}

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Apr 08 2013
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9904




07:47:34 PDT ---


 struct S1
 {
     int x;
 }
 
 struct S2
 {
     int x;
     byte b;
 }


Those should really use size_t to reproduce on all systems:


 struct S1
 {
     size_t x;
 }
 
 struct S2
 {
     size_t x;
     byte b;
 }


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prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9904


bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs eml.cc






 Those should really use size_t to reproduce on all systems:
 

 struct S1
 {
     size_t x;
 }
 
 struct S2
 {
     size_t x;
     byte b;
 }




Why is that cast a problem/bug? Maybe there is no compiler bug here.

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10:31:56 PDT ---



 

 Those should really use size_t to reproduce on all systems:
 

 struct S1
 {
     size_t x;
 }
 
 struct S2
 {
     size_t x;
     byte b;
 }




 
 Why is that cast a problem/bug? Maybe there is no compiler bug here.


It may not do what the user expects. For example they might think this is a
good way to initialize the struct to its default value, but it's wrong:

import std.math;

struct S
{
    float x;
}

void main()
{
    auto s1 = S.init;
    auto s2 = cast(S)null;
    assert(isnan(s1.x));
    assert(isnan(s2.x));  // fails
}

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/d859a617045bdf04b39edf14bb782faff642141a
fix issue 9904 - typeof(null) can be casted to aggregate type if .sizeof
equals size of pointer

https://github.com/D-Programming-Language/dmd/commit/3c5eb896fb87b788dd0cb7631fbdf8c5cf77d9f2


fix issue 9904 - typeof(null) can be casted to aggregate type if .sizeof equals
size of pointer

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Jun 07 2013
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9904


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

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



Merged pull request:
https://github.com/D-Programming-Language/dmd/pull/2148

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Jun 07 2013