Hello,
Some days ago, I did a conversion from a C header to Pascal, and I noticed
that H2Pas tool could implement a little bit improvement for Variadic[1]
(or varargs) functions conversion.
Consider the following C function with `varargs`:
int function foo(int bar, ...) {};
I can call this function in two ways:
1. foo("Bar");
2. foo("Bar", "some", "separed", "arguments", "without", "squared",
"braces").
Usually, H2Pas convert it overloaded:
function foo(bar: cint): cint; cdecl ...
function foo(bar: cint; args: array of const): cint; cdecl ...
And it doesn't work when a code needs to work both in FPC and Delphi. For
Delphi compiler, to compile the converted header, you needs to specify the
overload directive:
function foo(bar: cint): cint; cdecl; overload ...
function foo(bar: cint; args: array of const): cint; cdecl; overload ...
But, even specifying the overload, the converted function doesn't works in
Delphi. But someone can say: why Delphi, Mr? No special reason, currently I
just write code that needs to compile both in FPC and Delphi.
OK, but, how to declare a variadic function in FPC/Delphi? It is very easy:
function foo(bar: cint): cint; verargs; cdecl; ...
Let's go to read its documentation:
This modifier can only be used together with the cdecl modifier, for
> external C procedures. It indicates that the procedure accepts a variable
> number of arguments after the last declared variable. These arguments are
> passed on without any type checking. It is equivalent to using the array of
> const construction for cdecl procedures, without having to declare the
> array of const. The square brackets around the variable arguments do not
> need to be used when this form of declaration is used. [2]
Great! So, using the varargs directive, I can declare and use my function
more C-like. =)
We already use something like this in WriteLn/ReadLn, eg:
WriteLn('some', 'separed', 'arguments', 'without', 'squared', 'braces').
So, after this little explanation, what do you think about add a new param
in H2Pas tool? Something like:
-V Declare C variadic functions with varargs directive.
Thank you!
[1] https://en.wikipedia.org/wiki/Variadic_function
[2] http://www.freepascal.org/docs-html/ref/refsu83.html
--
Silvio Clécio
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