CTFE and -betterC

[Xavier Bigand]

As I am trying to do a dll that acts exactly like one written in C, I am trying to compile my code with the -betterC option. So I would not need the DllMain function.

I am not sure that I use the best syntax for my CTFE function to be able to make it works with the option -betterC and to maintain it after.

In particular I have following issues (my code is at the end of message) :
  * startsWith function doesn't compile with -betterC
  * can't put static before the first foreach
  * don't really now how to factorize small expressions (oglFunctionName , oglFunctionName,...)
  * how to make the code I generate less polluted by conditions and iterations? Certainly by naming some previously computed parts with alias?
  * after that how to see the generated result and debug?

Thank you in advance for any help.

module api_entry;

import std.stdio : writeln;
import std.algorithm.searching;

import missing_ogl;

import std.traits;
import std.meta;

static string implementFunctionsOf(string Module, bool removeARB = false)()
{
     import std.traits;
     import std.regex;
     import std.conv;

     mixin("import " ~ Module ~ ";");

     string	res;

     res ~= "extern (C) {\n";

     foreach (name; __traits(allMembers, mixin(Module)))
     {
         static if (name.startsWith("da_")
                    && mixin("isCallable!" ~ name))
         {
             alias derelict_oglFunctionName = Alias!(name[3..$]);
             alias oglFunctionName = derelict_oglFunctionName;
             alias returnType = Alias!(ReturnType!(mixin(name)).stringof);
             alias parametersType = Alias!(Parameters!(mixin(name)).stringof);

             static if (removeARB && name.endsWith("ARB"))
                 oglFunctionName = oglFunctionName[0..$ - 3];

             res ~=
                 "export\n" ~
                 returnType ~ "\n" ~
                 oglFunctionName ~
                 parametersType ~ "\n" ~
                 "{\n" ~
                 "    writeln(\"" ~ oglFunctionName ~ " is not specialized\");\n";

             // Forward the call to the driver (with arguments and return the
             // value of the forward directly)
             res ~= "import " ~ Module ~ ";";

             // For a reason I do not understand the compiler can not
             // compile with returnType
             static if (ReturnType!(mixin(name)).stringof == "int function()")
                 res ~=
                     "    alias extern (C) " ~ returnType ~ " returnType;\n" ~
                     "    return cast(returnType) ";
             else if (returnType != "void")
                 res ~=
                     "    return ";
             res ~=
                 "    " ~ Module ~ "." ~ derelict_oglFunctionName ~ "(";
             foreach (i, parameter; Parameters!(mixin(name)))
             {
                 if (i > 0)
                     res ~= ", ";
				// We use the default parameter name variable "_param_x" where x
				// is the index of the parameter starting from 0
                 res ~= "_param_" ~ to!string(i);
             }
             res ~=
                 ");";

             res ~=
                 "}\n";
         }
     }

     res ~=
         "}\n";
     return res;
}


mixin(implementFunctionsOf!("derelict.opengl3.functions"));
mixin(implementFunctionsOf!("derelict.opengl3.deprecatedFunctions"));