lastest bpftrace need -lstdc++fs

[b-ripper]

Hi,

The lastest bpftrace master need -lstdc++fs, current env not supported.
I found libc++fs is available on Android R AOSP source code(external/libcxx).
also available in projects/llvm/sources/libcxx.

So, use libc++fs instead of libstdc++fs?
Do you have any suggestion?

Very thanks

[michalgr]

So there are a few things we could try.

std::filesystem will be supported in ndk r22, at least according to this issue: android/ndk#609. But we're on r17 here for a reason (r18 removed gcc and libelf does not build with clang). Plus it's not obvious whether std::filesystem will be available on all the platforms we support (API 28+). The best way forward would be to move to r22 (if that works), but it won't happen soon.

Another way is to do what you suggest. We can compile our own libc++ as you suggest and link against that. It seems that we should be able to set ANDROID_STL to none to prevent ndk from providing its own stl.

I wonder whether we can do something quick to unblock you sooner. How much of libstdc++fs do we actually need ? Maybe we can just define our own filesystem header and define absolute and canonical functions in terms of realpath ?

[michalgr]

I just pushed 2b28f5e which updates version of bpftrace to current master. @b-ripper: does it solve problems you run into ?

[b-ripper]

Yes, thanks very much!