Misc fix

[chenhengqi]

1. code cleanup(comments, unused codes, indention etc.)
2. sync with latest libbpf, replace deprecated API usage and fix memory leak.

[tohojo]

Please drop the first commit; it's a tutorial, so it's not really supposed to
work out of the box...

[chenhengqi]

Done.

But it's strange that everyone cloning this repo has to resolve the compilation error before getting a successful build.

[tohojo]

Hengqi Chen ***@***.***> writes:

Done. But it's strange that everyone cloning this repo has to resolve the compilation error before getting a successful build.

It builds just fine on my system. I think maybe your compiler is picking up that -Wunused-but-set-variable from some system-wide setting? We don't set it in any of the Makefiles in the repository...

[chenhengqi]

I use clang-13, it fails. (clang 11/12 works fine.)

[tohojo]

Hengqi Chen ***@***.***> writes:

I use clang-13, it fails. (clang 11/12 works fine.)

Ah, so a new default, maybe? Could you please check if it helps to add -Wno-unused-but-set-variable to common.mk ?

[chenhengqi]

I believe it's a new flag in clang, no Google search results and documents for it currently.

It doesn't work in clang-12.

error: unknown warning option '-Wno-unused-but-set-variable'; did you mean '-Wno-unused-const-variable'? [-Werror,-Wunknown-warning-option]
make[1]: *** [../common//common.mk:111: xdp_prog_kern.o] Error 1
make[1]: Leaving directory '/home/xdp-tutorial/basic03-map-counter'
make: *** [Makefile:13: basic03-map-counter] Error 2

[tohojo]

Hengqi Chen ***@***.***> writes:

I believe it's a new flag in clang, no Google search results and documents for it currently.

Ah, that's because it has been backed out: llvm/llvm-project@6d8d133

[tohojo]

Toke Høiland-Jørgensen ***@***.***> writes:

Hengqi Chen ***@***.***> writes: > I believe it's a new flag in clang, no Google search results and > documents for it currently. Ah, that's because it has been backed out: llvm/llvm-project@6d8d133

Seems like it may come back, though: https://reviews.llvm.org/D100581 Does it get rid of the warning if you replace '-Wno-unused-value' with '-Wno-unused' in common.mk?

[chenhengqi]

I update to the latest nightly version, no complaints now.

How about just forget it and come back when it lands or clang-13 release ?

[tohojo]

Hengqi Chen ***@***.***> writes:

I update to the latest nightly version, no complaints now. How about just forget it and come back when it lands or clang-13 release ?

Fine with me :)