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Modula-2 is not the only language supporting unbounded arrays, I would be interested in using the same kind of code for pascal language support.

sure, I'm all for refactoring code..

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Maybe a more general approach would be useful?

maybe - although I suspect the devil is in the detail. Basically Modula-2 assumes that all unbounded arrays start at index 0 and the caller can be legally access all indices 0..HIGH(a). GNU Modula-2 implements unbounded arrays by creating a structure whose first field is a pointer to type, and the second structure is the HIGH value (unsigned int). So the patches basically detect if the array declaration matches a GNU Modula-2 unbounded structure (testing field names and types and language). If so then it maps any reference to a[i] onto a->_m2_contents[i] and HIGH(a) onto a->_m2_high. How does GNU Pascal implement unbounded arrays? This is basically also the case for parameter unbounded arrays: the valid indexes are from 0 to high(a) and high(a) is passed as an additional hidden parameter, called highA (high in lower case followed by the uppercase name of the parameter) for free pascal and open_array_length_0 (or _x for the X+1 open array parameter) for GNU pascal.

The open array type can be recongnized by the fact that the lower bound is 0, while the higher bound is -1. Free pascal now also supports global open array variables which are allocated by using SetLength function. They are basically hidden pointers. The high values is at offset -4 (or size of pointer more generally) relative to the pointer address. I don't know if GPC supports this syntax. Maybe someone from GPC team can answer this question. Pierre Muller