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Implementation notes


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Paragraphs and sections

There are two mechanisms of doing something (procedurally speaking) in cobol:

Our original implementation was to have a pair (end-of-paragraph/beginning-of-paragraph) placed at the stack frame. Instead of doing returns, we call a function to compute where we should go, by checking the address limits of the stacked paragraph. Because we are going to generate C code, we must be careful here, for the C compiler could do optimizations that change those addresses.

The idea is better caught with an example:

	DO_THIS.
		<SOME COBOL STATEMENTS>
	DO_THIS_OTHER.
		<COBOL STATEMENTS>
		PERFORM DO_THIS.
		<MORE COBOL STATEMENTS>
The program will execute all statements after DO_THIS paragraph, then follows to DO_THIS_OTHER. When found PERFORM DO_THIS, it will do again DO_THIS, but will return at the end of DO_THIS paragraph (just before the beginning of DO_THIS_OTHER). The same applies with sections, by grouping several paragraphs till the end of section.


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