问题

Background

I sometimes run into code that use the following dummy lambda-capture (instead of e.g. (void)x;, ... foo(int /* x */) or ... foo([[maybe_unused]] int x) in C++17) in order to remedy an unused variable warning:

void foo(int x)
{
    [&x]{}();
}

Now, this is not really a remedy, as it passes the warning over from the current scope to the lambda capture instead, but afaik, GCC has no diagnostic to flag this, whereas e.g. Clang (as of 5.0) emits the unused-lambda-capture warning, if activated.

$ clang++ -xc++ -std=c++11 -Wunused-lambda-capture - <<< "int main() { int x; [&x]{}(); }"

<stdin>:1:23: warning: lambda capture 'x' is not used [-Wunused-lambda-capture]
int main() { int x; [&x]{}(); }
                      ^
1 warning generated.

In GCC projects, I would if possible be able to catch constructs as the one above without resorting to Clang.

Question(s)

Is there indeed currently no equivalent for GCC?
If not, is that a feature that is currently planned to be implemented / currently being implemented?

回答1:

This is an open bug report for GCC

Is there indeed currently no equivalent for GCC?

This is indeed the case, as is covered by the very old but still open bug report:

Bug 52281 - No warnings generated for unused captures

If not, is that a feature that is currently planned to be implemented / currently being implemented?

Based on the lack of action on this bug report (reported and confirmed in 2012, seemingly not much happening since), this is not something that will likely be added soon.

来源：https://stackoverflow.com/questions/51616378/is-there-a-clang-wunused-lambda-capture-equivalent-warning-in-being-develop

标签

c++