trying to decrypt my first big program, which is a LISP interpreter, in this case. I am completely new to the world of understanding the code of another, and it seems much more complex than the encoding itself.
I can hardly create a minimal version of my current difficulty, since my current difficulty is to minimize the existing code in order to better understand it, and I encounter errors in almost every modification that I try to execute.
The interpreter uses the global variables Current_Input and Current_Output to abstractly read and write files and widgets from and to them. I'm just trying to get it to write to stdout.
Matching lines:
Current_Output = alloc_objet(sizeof(Widget *));
objet_type(Current_Output) = OWIDGET;
Owidget(Current_Output) = Wtext;
Select an object (uber type), telling it that its real type is "WIDGET", and assign it a Widget Wtext.
The OFILE type already exists and has an Ofile macro file, similar to the Owidget macro, that's all:
#define Owidget(objet) (* ((output_widget) objet + JMP))
#define Ofile(objet) ((FILE *) objet + JMP)
I wanted to replace the three matching lines with this:
Current_Output = alloc_objet(sizeof(FILE *));
objet_type(Current_Output) = OFILE;
Ofile(Current_Output) = stdout;
which causes the following error:
error: lvalue required as left operand of assignment Ofile(Current_Output) = stdout;
This line:
printf("%d", Ofile(Current_Output));
Throws this warning:
warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘FILE* {aka _IO_FILE*}’ [-Wformat=]
making me believe that I have a FILE * on the left side of the listening line to which I want to assign stdout to another FILE *.
What is wrong here? Thanks!