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4.41 Deprecated Features

In the past, the GNU C++ compiler was extended to experiment with new features, at a time when the C++ language was still evolving. Now that the C++ standard is complete, some of those features are superceded by superior alternatives. Using the old features might cause a warning in some cases that the feature will be dropped in the future. In other cases, the feature might be gone already.

While the list below is not exhaustive, it documents some of the options that are now deprecated:

-fthis-is-variable

In early versions of C++, assignment to this could be used to implement application-defined memory allocation. Now, allocation functions (`operator new') are the standard-conforming way to achieve the same effect.

-fexternal-templates

-falt-external-templates

These are two of the many ways for g++ to implement template instantiation. See section 5.5 Where's the Template?. The C++ standard clearly defines how template definitions have to be organized across implementation units. g++ has an implicit instantiation mechanism that should work just fine for standard-conforming code.