• cal (15/15) Nov 12 2012 Is the following a bug?
• simendsjo (8/23) Nov 12 2012 It's not a bug.
• cal (2/9) Nov 12 2012 Ah right of course, thank you.
• Andrej Mitrovic (2/3) Nov 12 2012 It's a bug, he's overwriting immutable data.
• Andrej Mitrovic (2/5) Nov 12 2012 Ahh sorry I completely misread the code. There's no bug here actually.
• Andrej Mitrovic (10/11) Nov 12 2012 Reduced:
• Andrej Mitrovic (2/4) Nov 12 2012 My bad, the string contents aren't being modified. Not a bug.

"cal" <callumenator gmail.com> writes:

Is the following a bug?

import std.c.string, core.memory;

void* makeNew(T)()
{
     T t = T.init;
     void* ptr = GC.malloc(T.sizeof);
     memcpy(ptr, &t, T.sizeof);
     return ptr;
}

void main()
{
     alias string T;
     T* iptr = cast(T*)makeNew!(T);
     (*iptr) = [1,2,3]; // this is allowed
}

"simendsjo" <simendsjo gmail.com> writes:

On Monday, 12 November 2012 at 21:03:51 UTC, cal wrote:
 Is the following a bug?

 import std.c.string, core.memory;

 void* makeNew(T)()
 {
     T t = T.init;
     void* ptr = GC.malloc(T.sizeof);
     memcpy(ptr, &t, T.sizeof);
     return ptr;
 }

 void main()
 {
     alias string T;
     T* iptr = cast(T*)makeNew!(T);
     (*iptr) = [1,2,3]; // this is allowed
 }

It's not a bug.

string is an alias for immutable(char)[].
ubyte can be implicitly converted to char.
All your numbers are less than 256, so dmd is able to convert 
them to char.
If you try this, it fails.
string s = [256]; // 256 is > char.max

"cal" <callumenator gmail.com> writes:

On Monday, 12 November 2012 at 21:08:43 UTC, simendsjo wrote:
 It's not a bug.

 string is an alias for immutable(char)[].
 ubyte can be implicitly converted to char.
 All your numbers are less than 256, so dmd is able to convert 
 them to char.
 If you try this, it fails.
 string s = [256]; // 256 is > char.max

Ah right of course, thank you.

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 11/12/12, simendsjo <simendsjo gmail.com> wrote:
 It's not a bug.

It's a bug, he's overwriting immutable data.

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 11/12/12, Andrej Mitrovic <andrej.mitrovich gmail.com> wrote:
 On 11/12/12, simendsjo <simendsjo gmail.com> wrote:
 It's not a bug.

 It's a bug, he's overwriting immutable data.

Ahh sorry I completely misread the code. There's no bug here actually.

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 11/12/12, cal <callumenator gmail.com> wrote:
 Is the following a bug?

Reduced:

void main()
{
    string x = "foo";
    string* y = &x;
    *y = [1, 2, 3];
    assert(x == "foo"); // fails
}

Yes this is a bug, especially since the string is typed as immutable(char)[].

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 11/12/12, Andrej Mitrovic <andrej.mitrovich gmail.com> wrote:
 Yes this is a bug, especially since the string is typed as
 immutable(char)[].

My bad, the string contents aren't being modified. Not a bug.