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15.3.12 Sensible Non-standard Constructs

g77 rejects things other compilers accept, like `INTRINSIC SQRT,SQRT'. As time permits in the future, some of these things that are easy for humans to read and write and unlikely to be intended to mean something else will be accepted by g77 (though -fpedantic should trigger warnings about such non-standard constructs).

Until g77 no longer gratuitously rejects sensible code, you might as well fix your code to be more standard-conforming and portable.

The kind of case that is important to except from the recommendation to change your code is one where following good coding rules would force you to write non-standard code that nevertheless has a clear meaning.

For example, when writing an INCLUDE file that defines a common block, it might be appropriate to include a SAVE statement for the common block (such as `SAVE /CBLOCK/'), so that variables defined in the common block retain their values even when all procedures declaring the common block become inactive (return to their callers).

However, putting SAVE statements in an INCLUDE file would prevent otherwise standard-conforming code from also specifying the SAVE statement, by itself, to indicate that all local variables and arrays are to have the SAVE attribute.

For this reason, g77 already has been changed to allow this combination, because although the general problem of gratuitously rejecting unambiguous and “safe” constructs still exists in g77, this particular construct was deemed useful enough that it was worth fixing g77 for just this case.

So, while there is no need to change your code to avoid using this particular construct, there might be other, equally appropriate but non-standard constructs, that you shouldn't have to stop using just because g77 (or any other compiler) gratuitously rejects it.

Until the general problem is solved, if you have any such construct you believe is worthwhile using (e.g. not just an arbitrary, redundant specification of an attribute), please submit a bug report with an explanation, so we can consider fixing g77 just for cases like yours.