Is the C ++ compiler or linker (by any C ++ standard) deleting an unused method? Compilers seem to be allowed to remove unused static functions, linkers are allowed to remove unused functions. But I did not find any information on how this looks for class methods. When the method is virtual, it becomes really interesting.
The C ++ standard works at a more abstract level. This does not require a C ++ implementation to actually consist of separate tools, such as a compiler and linker.
By the way, I was just looking for a draft PDF on my machine, and there is only one instance of the word “linker” in all 1368-pages, and even that is only in the footnote on page 22 about character sets.
What the standard is really talking about is the so-called as-if rule .
Citation §1.9:
(...) necessary to emulate (only) the observed behavior of an abstract machine, as described below.
The footnote for this proposal further states:
This provision is sometimes called the “as is” rule, since the implementation can freely ignore any requirements of this International Standard , as long as the result is as if the requirements were met , as far as it can be determined from the observed program behavior.
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Compilers could test how vtable instances are used to detect unused virtual members, but to track small benefits. GCC did not do this a few years ago.
Keyword volatileor export retains class variables and functions / methods when optimizations are removed.
volatile