Re: error forward references if scope
On Saturday, 12 March 2022 at 13:12:25 UTC, vit wrote:
```d
enum touch_T = __traits(hasMember, T, "touch");
```
I think you meant build instead of touch?
```d
struct Query {
public const SharedPtr!Builder builder;
}
interface Builder {
void build(ref Query query);
}
struct SharedPtr(T) {
enum touch_T = __traits(hasMember, T, "build");
}
import std.traits, std.stdio;
void main() {
Query q;
q.builder.touch_T.writeln(" #build");
} // true #build
```
error forward references if scope
Hello,
why this code compile without problems:
```d
struct Query{
public const SharedPtr!Builder builder;
}
interface Builder{
void build(ref Query query);
}
struct SharedPtr(T){
enum touch_T = __traits(hasMember, T, "touch");
//...
}
void main(){
}
```
but if `ref Query query` is scope then there is error?
```d
struct Query{
public const SharedPtr!Builder builder;
}
interface Builder{
void build(scope ref Query query); //SCOPE
}
struct SharedPtr(T){
enum touch_T = __traits(hasMember, T, "touch");
//...
}
void main(){
}
```
```
src/app.d(3,1): Error: no size because of forward references
src/app.d(4,18): Error: template instance
`app.SharedPtr!(Builder)` error instantiating
```
Re: Forward references
Hello there, I got a weird compilation error which was hard to debug (even for just a little program) and I thought, this is quite related to this thread. This is my error message: ``` ***search.d(42,1): Error: class ***.XXX has forward references ***box.d(21,32): Error: template instance *** error instantiating ***.d(16,2):instantiated from here: ... ... ``` It was odd, the fix was not obvious and the compiler didn't show me the place of the erroneous forward reference. The problem was a scoped `import` statement!! I had put the import statement for the Box class into the abstract base class Search, the only place where it is used, but this seems to cause a mess with many errors. The imported Box uses a sub class of Search as parameter type and since Search is extended by its subclasses it creates a circular reference in the subclass. The only way to fix was putting the import outside of the abstract base class (I assume because the import statement literally imports the Box together with the used subclass into Search itself). The lesson is, you cannot put your import just everywhere.
Re: std.container.array: Error: unable to determine fields of Test because of forward references
On Thursday, 31 October 2019 at 12:37:55 UTC, user1234 wrote:
struct S
{
S*[] children;
}
because otherwise when you declare the array the compiler has
not finished the semantic ana of S.
---
struct Test
{
Test[] t;
}
---
Works today. Putting pointers into the container (and thus having
another indirection) is not an option, though.
Re: std.container.array: Error: unable to determine fields of Test because of forward references
On Thursday, 31 October 2019 at 12:37:55 UTC, user1234 wrote:
On Thursday, 31 October 2019 at 12:29:28 UTC, Tobias Pankrath
wrote:
[...]
Try
struct S
{
S*[] children;
}
because otherwise when you declare the array the compiler has
not finished the semantic ana of S.
so S size is not known while S* size is known as it's a pointer
Re: std.container.array: Error: unable to determine fields of Test because of forward references
On Thursday, 31 October 2019 at 12:29:28 UTC, Tobias Pankrath
wrote:
My Problem:
--- (https://run.dlang.io/is/CfLscj)
import std.container.array;
import std.traits;
struct Test
{
Test[] t;
}
struct Test2
{
Array!Test2 t;
}
int main()
{
return FieldTypeTuple!Test.length + FieldTypeTuple!Test2;
}
---
I've found https://issues.dlang.org/show_bug.cgi?id=19407 but I
am not using separate compilation, just `dmd test.d`.
I want to have a tree structure like
---
struct S
{
S[] children;
}
---
but I do not want to rely on the GC and thus wanted to use a
custom array type. What's the best way to do this?
Try
struct S
{
S*[] children;
}
because otherwise when you declare the array the compiler has not
finished the semantic ana of S.
std.container.array: Error: unable to determine fields of Test because of forward references
My Problem:
--- (https://run.dlang.io/is/CfLscj)
import std.container.array;
import std.traits;
struct Test
{
Test[] t;
}
struct Test2
{
Array!Test2 t;
}
int main()
{
return FieldTypeTuple!Test.length + FieldTypeTuple!Test2;
}
---
I've found https://issues.dlang.org/show_bug.cgi?id=19407 but I
am not using separate compilation, just `dmd test.d`.
I want to have a tree structure like
---
struct S
{
S[] children;
}
---
but I do not want to rely on the GC and thus wanted to use a
custom array type. What's the best way to do this?
Re: class X has forward references
On 06/12/2018 01:14 PM, bauss wrote:
> What could cause that error?
Could be this point apparently during semantic analysis:
https://github.com/dlang/dmd/blob/4e35f945e3245467c7ae0abe60fc3ec896c8b45f/src/dmd/semantic2.d#L576
private extern(C++) final class Semantic2Visitor : Visitor
{
// ...
override void visit(AggregateDeclaration ad)
{
//printf("AggregateDeclaration::semantic2(%s) type = %s, errors
= %d\n", ad.toChars(), ad.type.toChars(), ad.errors);
if (!ad.members)
return;
if (ad._scope)
{
ad.error("has forward references");
return;
}
// ...
}
}
Does that mean that the scope pointer is already set when this
AggregateDeclaration is being visited? If it's a bug, perhaps someone
can think of a way of reproducing it.
Ali
Re: class X has forward references
On Tuesday, 12 June 2018 at 20:30:22 UTC, Steven Schveighoffer wrote: On 6/12/18 4:14 PM, bauss wrote: What could cause that error? I cannot find anything in the documentation nor does the error message itself give much information. A forward reference that can't be figured out by the compiler. This is one of the DMD front end's real weak spots. I can't really give a good example, but I can tell as much as I have a few inheritances of classes using templates. Yes, I've had weird forward reference errors in the past, and the only way I've been able to solve them is to move stuff around. I just don't think that would be the issue. When I try to make a minimized example it doesn't happen, so I'm going to assume it's either a function or a member or something in one of the inheritances that does it. It would be really helpful if I knew what I was looking for, because it's thousands of lines of code I have to dig through with trial and error. Have you tried dustmite? I would think at least it should print the symbol it's not able to resolve. -Steve Yeah I get the symbol that it cannot resolve. I'm moving stuff around now and the error has disappeared. Now I just have to fix all the errors related to moving stuff around. Thanks though!
Re: class X has forward references
On 6/12/18 4:14 PM, bauss wrote: What could cause that error? I cannot find anything in the documentation nor does the error message itself give much information. A forward reference that can't be figured out by the compiler. This is one of the DMD front end's real weak spots. I can't really give a good example, but I can tell as much as I have a few inheritances of classes using templates. Yes, I've had weird forward reference errors in the past, and the only way I've been able to solve them is to move stuff around. I just don't think that would be the issue. When I try to make a minimized example it doesn't happen, so I'm going to assume it's either a function or a member or something in one of the inheritances that does it. It would be really helpful if I knew what I was looking for, because it's thousands of lines of code I have to dig through with trial and error. Have you tried dustmite? I would think at least it should print the symbol it's not able to resolve. -Steve
class X has forward references
What could cause that error? I cannot find anything in the documentation nor does the error message itself give much information. I can't really give a good example, but I can tell as much as I have a few inheritances of classes using templates. I just don't think that would be the issue. When I try to make a minimized example it doesn't happen, so I'm going to assume it's either a function or a member or something in one of the inheritances that does it. It would be really helpful if I knew what I was looking for, because it's thousands of lines of code I have to dig through with trial and error.
Re: Forward references
On 2/25/18 6:53 PM, Jiyan wrote: On Sunday, 25 February 2018 at 22:20:13 UTC, Steven Schveighoffer wrote: On 2/25/18 4:25 PM, Jiyan wrote: [...] Looks like this was fixed in 2.064. What version of the compiler are you using? -Steve 2.077.0 It is really strange, it works now but there still seems to be some strangeness about forward references. There are frequently issues with forward references. They are supposed to always work, but it's not always the case. -Steve
Re: Forward references
On Sunday, 25 February 2018 at 22:20:13 UTC, Steven Schveighoffer wrote: On 2/25/18 4:25 PM, Jiyan wrote: [...] Looks like this was fixed in 2.064. What version of the compiler are you using? -Steve 2.077.0 It is really strange, it works now but there still seems to be some strangeness about forward references. Thanks till now i guess :P
Re: Forward references
On 2/25/18 4:25 PM, Jiyan wrote:
Hi,
is there any document or text describing forward references?
It is kinda strange, i implemented a list structure which is kinda like
this:
struct list(T)
{
private:
struct node
{
T val;
node* next;
node* prev;
}
node* head;
node* last;
size_t size;
.
}
The thing is when i implement following struct:
struct Tre
{
list!Tre a;
}
theoretically it should be constructable. But it gives me out a compiler
error about Forward reference. Ok maybe the compiler at this point cant
do that but ...
The strange thing is i somehow managed earlier without knowing to do
exactly this in a much more complicated struct.
Can somebody enlighten me about this?
Looks like this was fixed in 2.064.
What version of the compiler are you using?
-Steve
Re: Forward references
works for me with 2.076.
Forward references
Hi,
is there any document or text describing forward references?
It is kinda strange, i implemented a list structure which is
kinda like this:
struct list(T)
{
private:
struct node
{
T val;
node* next;
node* prev;
}
node* head;
node* last;
size_t size;
.
}
The thing is when i implement following struct:
struct Tre
{
list!Tre a;
}
theoretically it should be constructable. But it gives me out a
compiler error about Forward reference. Ok maybe the compiler at
this point cant do that but ...
The strange thing is i somehow managed earlier without knowing to
do exactly this in a much more complicated struct.
Can somebody enlighten me about this?
Forward References
Do the various D compilers use multiple passes to handle forward references or some other technique?
Re: Forward references and more
T.sizeof must be 8 in all cases. Ignore this line, please :-)
Re: Forward references and more
On Mon, 12 Oct 2009 05:26:58 -0400, bearophile bearophileh...@lycos.com
wrote:
What's wrong with this code?
struct MemoryPool(T) {
alias T[100_000 / T.sizeof] Chunk;
Chunk*[] chunks;
}
struct Foo {
int x;
MemoryPool!(Foo) pool;
}
void main() {}
It prints Error: struct problem.Foo no size yet for forward reference.
T.sizeof must be 8 in all cases.
So I have tried to pull pool out:
struct MemoryPool(T) {
alias T[100_000 / T.sizeof] Chunk;
Chunk*[] chunks;
}
MemoryPool!(Foo) pool;
struct Foo {
int x;
// here uses pool
}
void main() {}
But there's a problem still:
Error: struct problem2.Foo no size yet for forward reference
To compile the code I have to move pool forward still:
struct MemoryPool(T) {
alias T[100_000 / T.sizeof] Chunk;
Chunk*[] chunks;
}
struct Foo {
int x;
// here uses pool
}
MemoryPool!(Foo) pool;
void main() {}
When possible it's better to avoid global variables. To avoid the global
variable I may pass the instance pool to Foo. But to do this Foo has to
become a struct template. But I am not sure how I can do this.
Do you have any comments or suggestions?
It looks strange what you are doing. A Foo can have a memory pool of a
lot of Foo's? Do you mean to make the memory pool static? I think that
might work.
I think the main problem is you are defining MemoryPool!(Foo).Chunk which
specifically needs to know the size of Foo before Foo is completely
declared.
It's like you are doing this:
struct X
{
X x;
}
Which clearly is incorrect.
-Steve
Re: Forward references and more
Steven Schveighoffer wrote:
On Mon, 12 Oct 2009 05:26:58 -0400, bearophile
bearophileh...@lycos.com wrote:
What's wrong with this code?
struct MemoryPool(T) {
alias T[100_000 / T.sizeof] Chunk;
Chunk*[] chunks;
}
struct Foo {
int x;
MemoryPool!(Foo) pool;
}
void main() {}
It prints Error: struct problem.Foo no size yet for forward reference.
T.sizeof must be 8 in all cases.
The compiler does this:
Instantiate MemoryPool!(Foo)
But for that it needs to know Foo.sizeof.
But for that it needs to know MemoryPool!(Foo).sizeof.
But for that it needs to instantiate MemoryPool!(Foo) and find it's size.
etc.
I can see MemoryPool!(Foo) sizeof doesn't depend at all of T.sizeof
because it just has a pointer. But how do you suggest to fix the
compiler to understand that?
What I can see is that to know MemoryPool!(Foo).sizeof the type of the
alias doesn't need to be solved completely... but what would you
recommend the compiler to do?
Re: Forward references and more
Ary Borenszweig: I can see MemoryPool!(Foo) sizeof doesn't depend at all of T.sizeof because it just has a pointer. Well, a dynamic array of pointers, but the situation is the same. But how do you suggest to fix the compiler to understand that? I don't know. I don't know enough about compilers. What I can see is that to know MemoryPool!(Foo).sizeof the type of the alias doesn't need to be solved completely... but what would you recommend the compiler to do? To see what I can see. And terminate this little dance. If that's not possible, then I'd like to have a syntax to give the necessary hint to the (less than smart) compiler. For example saying the size of one or both structs. This was just an example, but it's not the first time I fall in this problem when I create data structures in D. Bye and thank you, bearophile
Re: Forward references and more
On Mon, 12 Oct 2009 15:38:07 -0400, bearophile bearophileh...@lycos.com
wrote:
Steven Schveighoffer:
It looks strange what you are doing. A Foo can have a memory pool of a
lot of Foo's? Do you mean to make the memory pool static?
Right and yes.
I think that might work.
It works if I use a global variable. But I'd like to not used global
variables when possible.
A static variable is essentially a scoped global variable. I think it
will work if you make it static. I've used plenty of static variables
that are instances of the struct they are declared in.
I think the main problem is you are defining MemoryPool!(Foo).Chunk
which
specifically needs to know the size of Foo before Foo is completely
declared.
It's like you are doing this:
struct X
{
X x;
}
Which clearly is incorrect.
But MemoryPool.sizeof is always 8 (on a 32 bit system) because an alias
takes no space. So T.sizeof must be 12. I'd like the compiler to
understand this.
But you are also declaring the type of the chunk. I don't think it would
complain if you were not trying to define a type that required the size of
Foo. For example, if you did something like:
struct MemoryPool(T)
{
T[] chunks;
}
I think it would work, because you aren't trying to define a type which
*requires* the size of T before T is fully declared. It's sort of a
chicken and egg thing. But since I think you are implementing the memory
pool incorrectly (it makes no sense for each instance of an item to have a
pool of itself), you should reexamine what you are trying to do.
-Steve
Re: x has forward references
Jacob Carlborg Wrote:
It works with dmd 1.045
Where to get it?
I also tried compiling derelict today. I finally managed to get past the error
messages by using the dmd compiler that ships with tango. 1.033 if I remember
correctly. The lib folder filled up nicely with files. Then I did a dsss
install command. The libs now show up in the dsss/lib folder and there are .di
files in the include/derelict folder.
So I tried to compile a little test.d
module derelicttest;
import derelict.opengl.gl;
void main()
{
DerelictGL.load();
}
The dsss.conf:
[*]
buildflags = -g -gc
[test.d]
I don't know what else to put in there. I'm compiling with dmd 1.046. And get
the following message.
D:\Workshop\D\derelictdsss build
test.d = test
OPTLINK (R) for Win32 Release 8.00.1
Copyright (C) Digital Mars 1989-2004 All rights reserved.
D:\Workshop\D\dsss\lib\\DerelictGL.lib(gl)
Error 42: Symbol Undefined _D6object9Exception5_ctorMFAaC9ExceptionZC9Exception
--- errorlevel 1
Command D:\Workshop\D\dsss\bin\rebuild.exe returned with code -1, aborting.
Error: Command failed, aborting.
If I try it with the 1.033 compiler that ships with tango the list of messages
is similar but even longer.
Re: x has forward references
On 8/16/09 19:36, Jos van Uden wrote:
Jacob Carlborg Wrote:
It works with dmd 1.045
Where to get it?
http://www.digitalmars.com/d/1.0/changelog.html#new1_045
I also tried compiling derelict today. I finally managed to get past the error
messages by using the dmd compiler that ships with tango. 1.033 if I remember
correctly. The lib folder filled up nicely with files. Then I did a dsss
install command. The libs now show up in the dsss/lib folder and there are .di
files in the include/derelict folder.
So I tried to compile a little test.d
module derelicttest;
import derelict.opengl.gl;
void main()
{
DerelictGL.load();
}
The dsss.conf:
[*]
buildflags = -g -gc
[test.d]
I don't know what else to put in there. I'm compiling with dmd 1.046. And get
the following message.
D:\Workshop\D\derelictdsss build
test.d = test
OPTLINK (R) for Win32 Release 8.00.1
Copyright (C) Digital Mars 1989-2004 All rights reserved.
D:\Workshop\D\dsss\lib\\DerelictGL.lib(gl)
Error 42: Symbol Undefined
_D6object9Exception5_ctorMFAaC9ExceptionZC9Exception
--- errorlevel 1
Command D:\Workshop\D\dsss\bin\rebuild.exe returned with code -1, aborting.
Error: Command failed, aborting.
If I try it with the 1.033 compiler that ships with tango the list of messages
is similar but even longer.
Re: x has forward references
Spacen Jasset Wrote: Jos van Uden wrote: Jacob Carlborg Wrote: On 8/16/09 19:36, Jos van Uden wrote: Jacob Carlborg Wrote: It works with dmd 1.045 Where to get it? http://www.digitalmars.com/d/1.0/changelog.html#new1_045 Thank you. This version does indeed compile the libs, just like 1.033, but I still get the same error when I try to compile the test. When I do the DerelictAL test (alinfo) that comes with the derelict download, it compiles and runs just fine. Try zapping all the derelict object and lib files. That did the trick. Thanks.
Re: x has forward references
On 8/13/09 17:01, Spacen Jasset wrote: Hello, trying to use deteclit with the latest version of dmd 1.047 and I get this error. I don't understand what it means: derelict\freetype\fttypes.d(827): Error: struct derelict.freetype.fttypes.FT_RasterRec has forward references line 97: alias FT_RasterRec* FT_Raster; line 827: struct FT_RasterRec; If use use dmd 1.046 it probably means you hit this bug: http://d.puremagic.com/issues/show_bug.cgi?id=3168 It works with dmd 1.045 /Jacob Carlborg
