digitalmars.D.learn - Cannot cast void* to arrays..?
- simendsjo (4/4) Feb 24 2012 char[] a;
- Justin Whear (3/8) Feb 24 2012 Arrays have a length--you need to cast the pointer to a char*, then slic...
- simendsjo (9/17) Feb 24 2012 Ah, of course, thanks.
- =?UTF-8?B?QWxpIMOHZWhyZWxp?= (4/23) Feb 24 2012 char[1] a;
- simendsjo (9/36) Feb 24 2012 =
- Andrej Mitrovic (3/8) Feb 24 2012 You can do:
- simendsjo (4/13) Feb 24 2012 Thanks! I had to do an explicit cast(char[1]) (or actually char[1][1] in...
- H. S. Teoh (9/11) Feb 24 2012 [...]
- H. S. Teoh (8/12) Feb 24 2012 D arrays are not the same as C arrays. D arrays also include length in
- Mantis (4/8) Feb 24 2012 Generally, you should not cast a struct to pointer and vise-versa.
- H. S. Teoh (8/13) Feb 24 2012 [...]
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simendsjo
(11/20)
Feb 24 2012
On Fri, 24 Feb 2012 20:56:22 +0100, H. S. Teoh
char[] a;
auto b = cast(void*)a;
auto c = cast(char[])b; // Error: e2ir: cannot cast b of type void* to
type char[]
Feb 24 2012
On Fri, 24 Feb 2012 20:34:19 +0100, simendsjo wrote:
char[] a;
auto b = cast(void*)a;
auto c = cast(char[])b; // Error: e2ir: cannot cast b of type void*
to
type char[]
Arrays have a length--you need to cast the pointer to a char*, then slice
it.
Feb 24 2012
On Fri, 24 Feb 2012 20:42:20 +0100, Justin Whear <justin economicmodeling.com> wrote:On Fri, 24 Feb 2012 20:34:19 +0100, simendsjo wrote:Ah, of course, thanks. But what about static arrays? char[1] a; //a.length = 10; // constant a.length is not an lvalue auto b = cast(void*)a; auto c = cast(char[1])b; // Error: e2ir: cannot cast b of type void* to type char[1LU]char[] a; auto b = cast(void*)a; auto c = cast(char[])b; // Error: e2ir: cannot cast b of type void* to type char[]Arrays have a length--you need to cast the pointer to a char*, then slice it.
Feb 24 2012
On 02/24/2012 11:44 AM, simendsjo wrote:On Fri, 24 Feb 2012 20:42:20 +0100, Justin Whear <justin economicmodeling.com> wrote:char[1] a; auto c = a.ptr[0..a.length]; AliOn Fri, 24 Feb 2012 20:34:19 +0100, simendsjo wrote:Ah, of course, thanks. But what about static arrays? char[1] a; //a.length = 10; // constant a.length is not an lvalue auto b = cast(void*)a; auto c = cast(char[1])b; // Error: e2ir: cannot cast b of type void* to type char[1LU]char[] a; auto b = cast(void*)a; auto c = cast(char[])b; // Error: e2ir: cannot cast b of type void* to type char[]Arrays have a length--you need to cast the pointer to a char*, then slice it.
Feb 24 2012
On Fri, 24 Feb 2012 20:56:18 +0100, Ali =C3=87ehreli <acehreli yahoo.com=wrote:On 02/24/2012 11:44 AM, simendsjo wrote:d*On Fri, 24 Feb 2012 20:42:20 +0100, Justin Whear <justin economicmodeling.com> wrote:On Fri, 24 Feb 2012 20:34:19 +0100, simendsjo wrote:char[] a; auto b =3D cast(void*)a; auto c =3D cast(char[])b; // Error: e2ir: cannot cast b of type voi==to type char[]Arrays have a length--you need to cast the pointer to a char*, then =* toslice it.Ah, of course, thanks. But what about static arrays? char[1] a; //a.length =3D 10; // constant a.length is not an lvalue auto b =3D cast(void*)a; auto c =3D cast(char[1])b; // Error: e2ir: cannot cast b of type void=I don't get it. This gives me a dynamic array, not a static: char[1] a; auto b =3D cast(void*)a; auto c =3D (cast(char*)b)[0..1]; c.length =3D 10; // auch!type char[1LU]char[1] a; auto c =3D a.ptr[0..a.length]; Ali
Feb 24 2012
On 2/24/12, simendsjo <simendsjo gmail.com> wrote:
I don't get it. This gives me a dynamic array, not a static:
char[1] a;
auto b = cast(void*)a;
auto c = (cast(char*)b)[0..1];
c.length = 10; // auch!
You can do:
char[1] c = (cast(char*)b)[0..1];
Feb 24 2012
simendsjo <simendsjo gmail.com> On Fri, 24 Feb 2012 21:36:21 +0100, Andrej Mitrovic <andrej.mitrovich gmail.com> wrote:On 2/24/12, simendsjo <simendsjo gmail.com> wrote:Thanks! I had to do an explicit cast(char[1]) (or actually char[1][1] in my case.)I don't get it. This gives me a dynamic array, not a static: char[1] a; auto b = cast(void*)a; auto c = (cast(char*)b)[0..1]; c.length = 10; // auch!You can do: char[1] c = (cast(char*)b)[0..1];
Feb 24 2012
On Fri, Feb 24, 2012 at 11:56:18AM -0800, Ali Çehreli wrote:
[...]
char[1] a;
auto c = a.ptr[0..a.length];
[...]
Hey, that's an awesome way to implement copy-on-write static arrays!
I'll have to use that sometime. :)
T
--
Sometimes the best solution to morale problems is just to fire all of
the unhappy people. -- despair.com
Feb 24 2012
On Fri, Feb 24, 2012 at 08:34:19PM +0100, simendsjo wrote:
char[] a;
auto b = cast(void*)a;
auto c = cast(char[])b; // Error: e2ir: cannot cast b of type
void* to type char[]
D arrays are not the same as C arrays. D arrays also include length in
addition to the pointer, so you can't just cast a void* to an array.
T
--
Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are, by
definition, not smart enough to debug it. -- Brian W. Kernighan
Feb 24 2012
24.02.2012 21:34, simendsjo пишет:
char[] a;
auto b = cast(void*)a;
auto c = cast(char[])b; // Error: e2ir: cannot cast b of type
void* to type char[]
Generally, you should not cast a struct to pointer and vise-versa.
Besides, size of array structure is larger than size of pointer, and
that triggers error in your case.
Feb 24 2012
24.02.2012 21:34, simendsjo пишет:[...] Just out of curiosity, what are you trying to accomplish with this cast? In almost all normal D code, there's no need for any casting at all. T -- The right half of the brain controls the left half of the body. This means that only left-handed people are in their right mind. -- Manoj Srivastavachar[] a; auto b = cast(void*)a; auto c = cast(char[])b; // Error: e2ir: cannot cast b of type void* to type char[]
Feb 24 2012
On Fri, 24 Feb 2012 20:56:22 +0100, H. S. Teoh <hsteoh quickfur.ath.cx> = = wrote:t?24.02.2012 21:34, simendsjo =D0=BF=D0=B8=D1=88=D0=B5=D1=82:[...] Just out of curiosity, what are you trying to accomplish with this cas=char[] a; auto b =3D cast(void*)a; auto c =3D cast(char[])b; // Error: e2ir: cannot cast b of type void* to type char[]In almost all normal D code, there's no need for any casting at all. TInteracting with a C callback taking a void*. In my callback, I want to = = get the same type back. See my previous question: = http://forum.dlang.org/post/op.v963zyg0x8p62v simendsjo-desktop (althoug= h = I didn't include the parameters in that example)
Feb 24 2012