Is there any way to output information at compile time other than pragma(msg?
pragma is driving me crazy, the following doesn't work:

auto members = __traits(allMembers, typeof(this));
foreach(m; members)
{
	pragma(msg, m);
}

-> Error: string expected for message, not 'm'

Though the docs clearly state:
allMembers: "An array of string literals is returned"
Also checked that, m is of type invariant(char)[].


Any ideas? -.-

On Wed, Jan 21, 2009 at 12:36 AM, Trass3r <mrmocool@gmx.de> wrote:
> Is there any way to output information at compile time other than
> pragma(msg?
> pragma is driving me crazy, the following doesn't work:
>
> auto members = __traits(allMembers, typeof(this));
> foreach(m; members)
> {
>        pragma(msg, m);
> }
>
> -> Error: string expected for message, not 'm'
>
> Though the docs clearly state:
> allMembers: "An array of string literals is returned"
> Also checked that, m is of type invariant(char)[].
>
>
> Any ideas? -.-

try indexing explicitly or using ref:

foreach(i,m; members)
{
    pragma(msg, members[i]);
}

foreach(ref m; members)
{
    pragma(msg, m);
}

Latter one may not be useful.  I can't recall.
--bb

Trass3r wrote:
> Is there any way to output information at compile time other than pragma(msg?
> pragma is driving me crazy, the following doesn't work:
> 
> auto members = __traits(allMembers, typeof(this));

Kind of offtopic, but I tried this (with typeof(Foo) and Foo is defined in the same module) in Descent and I get a NullPointerException. :-(

I thought the port to Java was wrong so I compared to dmd's code.

In traits.c I can see:

---
else if (ident == Id::allMembers || ident == Id::derivedMembers)
    {
	if (dim != 1)
	    goto Ldimerror;
	Object *o = (Object *)args->data[0];
	Dsymbol *s = getDsymbol(o);
---

and in template.c getDsymbol says:

---
Dsymbol *getDsymbol(Object *oarg)
{
    Dsymbol *sa;
    Expression *ea = isExpression(oarg);
    if (ea)
    {
        // (snip)
    }
    else
    {   // Try to convert Type to symbol
	Type *ta = isType(oarg);
	if (ta)
	    sa = ta->toDsymbol(NULL);
	else
	    sa = isDsymbol(oarg);	// if already a symbol
    }
    return sa;
}
---

and of course oarg is a type, it's a TypeTypeof, so TypeTypeof::toDsymbol is invoked. Note that in this point sc is NULL.

---
Dsymbol *TypeTypeof::toDsymbol(Scope *sc)
{
    Type *t;

    t = semantic(0, sc);
    if (t == this)
	return NULL;
    return t->toDsymbol(sc);
}
---

and finally...

---
Type *TypeTypeof::semantic(Loc loc, Scope *sc)
{   Expression *e;
    Type *t;

	sc->intypeof++; // sc is NULL!!
	exp = exp->semantic(sc);
	sc->intypeof--;

   // (snip)
}
---

and that's why I get a NPE. But compiling with dmd works fine. Unfortunately I don't have with me the necessary stuff to debug dmd... does anyone know what's going on?

Thanks,
Ary

Bill Baxter schrieb:
> try indexing explicitly or using ref:
> 
> foreach(i,m; members)
> {
>     pragma(msg, members[i]);
> }
> 
> foreach(ref m; members)
> {
>     pragma(msg, m);
> }
> 
> Latter one may not be useful.  I can't recall.

Neither one works for me :(

Reply to Trass3r,

> Is there any way to output information at compile time other than
> pragma(msg?
> pragma is driving me crazy, the following doesn't work:
> auto members = __traits(allMembers, typeof(this));
> foreach(m; members)
> {
> pragma(msg, m);
> }
> -> Error: string expected for message, not 'm'
> 
> Though the docs clearly state:
> allMembers: "An array of string literals is returned"
> Also checked that, m is of type invariant(char)[].
> Any ideas? -.-
> 

I don't do 2.0 but it looks to me like your mixing runtime and compile time stuff. A foreach over an array is a runtime foreach.

BCS schrieb:
> I don't do 2.0 but it looks to me like your mixing runtime and compile time stuff. A foreach over an array is a runtime foreach.
> 

Do you know how I could make it run at compile-time?

Reply to Trass3r,

> BCS schrieb:
> 
>> I don't do 2.0 but it looks to me like your mixing runtime and
>> compile time stuff. A foreach over an array is a runtime foreach.
>> 
> Do you know how I could make it run at compile-time?
> 

template Tpl(T...)
{
 alias T Tpl;
}

template Range(int l, int u)
{
 static if(l<u)
   alias Tpl!(l, Range!(l+1,u)) Range;
 else
   alias Tpl!(l) Range;
}

const char[][] set = ["Hello"[], "world" ];

void main()
{
 foreach(str; Range!(0,set.length-1)) // compile time foreach over the numbers from 0 to set.length-1
   pragma(msg, set[str]);
}

Tue, 20 Jan 2009 16:36:09 +0100, Trass3r wrote:

> Is there any way to output information at compile time other than
> pragma(msg?
> pragma is driving me crazy, the following doesn't work:
> 
> auto members = __traits(allMembers, typeof(this));
> foreach(m; members)
> {
> 	pragma(msg, m);
> }
> 
> -> Error: string expected for message, not 'm'
> 
> Though the docs clearly state:
> allMembers: "An array of string literals is returned"
> Also checked that, m is of type invariant(char)[].
> 
> Any ideas? -.-

Weird.  The following code does not compile:

class Cls
{
  int bar;
  char[] baz;
}
string foo()
{
  auto members = __traits(allMembers, Cls);
  return "";
}
pragma(msg, foo());

>dmd -c test.d
test.d(11): Error: cannot evaluate foo() at compile time
test.d(11): pragma msg string expected for message, not 'foo()'

Comment out the traits and it compiles.  Traits are supposed to be compile-time.  How's that possible for them to prevent compile-time evaluation?

BCS schrieb:
> template Tpl(T...)
> {
>  alias T Tpl;
> }
> 
> template Range(int l, int u)
> {
>  static if(l<u)
>    alias Tpl!(l, Range!(l+1,u)) Range;
>  else
>    alias Tpl!(l) Range;
> }
> 
> const char[][] set = ["Hello"[], "world" ];
> 
> void main()
> {
>  foreach(str; Range!(0,set.length-1)) // compile time foreach over the numbers from 0 to set.length-1
>    pragma(msg, set[str]);
> }
> 

Still doesn't work for this code (used with a mixin):
template classMixin()
{
static this()
{
	auto members = __traits(allMembers, typeof(this));
	foreach(m; Range!(0, members.length-1))
	{
		pragma(msg, members[m]);
		static if (is (typeof(__traits(getMember, this, members[m])) F == function))
		{
			pragma(msg, "function");
		}
	}
}
}

-> Error: string expected for message, not 'members[0u]'

Leaving out the first pragma, compiles but doesn't output anything.
Replacing members[m] with a valid method name, such as "__ctor" it outputs function correctly :(

Sergey Gromov schrieb:
 > class Cls
> {
>   int bar;
>   char[] baz;
> }
> string foo()
> {
>   auto members = __traits(allMembers, Cls);
>   return "";
> }
> pragma(msg, foo());
> 
>> dmd -c test.d
> test.d(11): Error: cannot evaluate foo() at compile time
> test.d(11): pragma msg string expected for message, not 'foo()'
> 
> Comment out the traits and it compiles.  Traits are supposed to be
> compile-time.  How's that possible for them to prevent compile-time
> evaluation?

Seeing this really simple example crashing makes me think that this has to be a bug.