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digitalmars.D.bugs - [Issue 2990] New: TypeInfo.init() returns invalid array

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2990

           Summary: TypeInfo.init() returns invalid array
           Product: D
           Version: 1.044
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: nfxjfg gmail.com


Sometimes, the array TypeInfo.init() returns has a length, but ptr is null.
Accessing an element of such an array causes segfaults. This can't be right.
TypeInfo.init() should just return an empty array.

Example follows. This outputs "ptr=0000 length=4".

import std.stdio;

struct X {
   int y;
}

void main() {
   TypeInfo ti = typeid(X);
   writefln("ptr=%s length=%s", ti.init.ptr, ti.init.length);
}

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May 16 2009
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2990


nfxjfg gmail.com changed:

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


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Jan 06 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2990


Brad Roberts <braddr puremagic.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |braddr puremagic.com
         Resolution|WONTFIX                     |


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Jan 06 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Steven Schveighoffer <schveiguy yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |schveiguy yahoo.com


--- Comment #1 from Steven Schveighoffer <schveiguy yahoo.com> 2011-01-07
06:46:51 PST ---
This is really a documentation issue.  The init() is correct, as I discovered
when fixing a recent bug.

Essentially, when the ptr is null, but the length is non-zero, the meaning is
that the init value for that type is init().length bytes of zero.  This cuts
down on having to store an array of zeros in the binary.

The documentation for init() says:

"Return default initializer, null if default initialize to 0"

Which seems to indicate init() should return null if default initializer should
be zero.  But a null array has length == 0.

I think the right solution to this is to change the documentation:

"Return default initializer.  If the type should be initialized to all zeros,
an array with a null ptr and a length equal to the type size will be returned"

Sound good?

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Jan 07 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla digitalmars.com


--- Comment #2 from Walter Bright <bugzilla digitalmars.com> 2011-04-05
11:31:07 PDT ---
This is deliberate, see the typinf.c code:

    // void[] init;
    dtsize_t(pdt, sd->structsize);       // init.length
    if (sd->zeroInit)
        dtsize_t(pdt, 0);                // NULL for 0 initialization
    else
        dtxoff(pdt, sd->toInitializer(), 0, TYnptr);    // init.ptr

I'll fix the documentation.

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Apr 05 2011
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2990


Walter Bright <bugzilla digitalmars.com> changed:

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


--- Comment #3 from Walter Bright <bugzilla digitalmars.com> 2011-04-05
11:41:20 PDT ---
https://github.com/D-Programming-Language/druntime/commit/a771c11bfe357ac2c6c87e96b39e8986286222f5

https://github.com/D-Programming-Language/phobos/commit/50a73bef9ac0e6f8bbc713c1ded85a8254175feb

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Apr 05 2011