https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71402
--- Comment #6 from andysem at mail dot ru --- (In reply to Martin Sebor from comment #5) > I understand that and agree that there is a set of use cases where users > don't expect a warning. There is also another set of cases where a warning > would be helpful: If the unused variable in the submitted test case were > the result of code changes that removed its uses and the variable was left > defined unintentionally, the user would be served by having this pointed > out. Otherwise the dynamic initialization would waste resources. I think issuing a warning about a perfectly valid code with no reasonable confidence about the code being written by mistake does a poor job for the user and encourages him to just disable the warning (possibly missing the real mistakes that would have been highlighted by the warning). > Adding a new warning (let's call it > -Wunused-varible-with-dynamic-initializer) would be one way to provide the > functionality that I think would be of use. If the warning for a variable that has dynamic initialization is indeed considered useful then I vote for the new flag solution. But frankly I think in practice this warning would be next to useless (e.g. it would have to highlight almost every mutex lock or scope guard). > Another solution would be to issue the -Wunused-variable warning for the > submitted test case and recommend users to annotate otherwise unused > variables with attribute unused to suppress the warning. This approach > would also be in line with the intended use of the new (in C++ 17) > maybe_unused attribute (proposed in WG21 document P0212R1). There are large code bases that don't excersize non-portable compiler features like attributes. One such example is libresiprocate, which has quite a few flags like the one I described in public headers. This is what actually led to this bug report. Also, I'll add that the warning cannot be silenced with a #pragma, so I can't, for example, disable it for libresiprocate headers and leave it enabled for my code.
