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(g77-295.info)Better Warnings

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Better Warnings
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   Because of how `g77' generates code via the back end, it doesn't
always provide warnings the user wants.  Consider:

     PROGRAM X
     PRINT *, A
     END

   Currently, the above is not flagged as a case of using an
uninitialized variable, because `g77' generates a run-time library call
that looks, to the GBE, like it might actually *modify* `A' at run time.
(And, in fact, depending on the previous run-time library call, it
would!)

   Fixing this requires one of the following:

   * Switch to new library, `libg77', that provides a more "clean"
     interface, vis-a-vis input, output, and modified arguments, so the
     GBE can tell what's going on.

     This would provide a pretty big performance improvement, at least
     theoretically, and, ultimately, in practice, for some types of
     code.

   * Have `g77' pass a pointer to a temporary containing a copy of `A',
     instead of to `A' itself.  The GBE would then complain about the
     copy operation involving a potentially uninitialized variable.

     This might also provide a performance boost for some code, because
     `A' might then end up living in a register, which could help with
     inner loops.

   * Have `g77' use a GBE construct similar to `ADDR_EXPR' but with
     extra information on the fact that the item pointed to won't be
     modified (a la `const' in C).

     Probably the best solution for now, but not quite trivial to
     implement in the general case.  Worth considering after `g77' 0.6
     is considered pretty solid.