depends: Fix compiling libevent package on NetBSD #31500

1. 
   hebasto commented at 3:41 pm on December 14, 2024: member

   Libevent introduced the typeof C language extension in the NetBSD-specific code, which was pulled into our depends in #21991.

   However, GCC states:

   the various -std options disable certain keywords.

   Due to our use of https://github.com/bitcoin/bitcoin/blob/b042c4f0538c6f9cdf8efbcef552796851e38a85/depends/hosts/netbsd.mk#L1

   the typeof keyword is disabled, resulting in a compilation error:

    0$ gmake -C depends libevent CC=/usr/pkg/gcc14/bin/gcc CXX=/usr/pkg/gcc14/bin/g++
    1<snip>
    2[ 37%] Building C object CMakeFiles/event_core_static.dir/kqueue.c.o
    3/home/hebasto/dev/bitcoin/depends/work/build/x86_64-unknown-netbsd10.0/libevent/2.1.12-stable-ca6b96ec97c/kqueue.c: In function 'kq_setup_kevent':
    4/home/hebasto/dev/bitcoin/depends/work/build/x86_64-unknown-netbsd10.0/libevent/2.1.12-stable-ca6b96ec97c/kqueue.c:56:27: error: implicit declaration of function 'typeof' [-Wimplicit-function-declaration]
    5   56 | #define INT_TO_UDATA(x) ((typeof(((struct kevent *)0)->udata))(intptr_t)(x))
    6      |                           ^~~~~~
    7/home/hebasto/dev/bitcoin/depends/work/build/x86_64-unknown-netbsd10.0/libevent/2.1.12-stable-ca6b96ec97c/kqueue.c:190:30: note: in expansion of macro 'INT_TO_UDATA'
    8  190 |                 out->udata = INT_TO_UDATA(ADD_UDATA);
    9      |                              ^~~~~~~~~~~~
   10/home/hebasto/dev/bitcoin/depends/work/build/x86_64-unknown-netbsd10.0/libevent/2.1.12-stable-ca6b96ec97c/kqueue.c:56:64: error: expected expression before 'intptr_t'
   11   56 | #define INT_TO_UDATA(x) ((typeof(((struct kevent *)0)->udata))(intptr_t)(x))
   12      |                                                                ^~~~~~~~
   13/home/hebasto/dev/bitcoin/depends/work/build/x86_64-unknown-netbsd10.0/libevent/2.1.12-stable-ca6b96ec97c/kqueue.c:190:30: note: in expansion of macro 'INT_TO_UDATA'
   14  190 |                 out->udata = INT_TO_UDATA(ADD_UDATA);
   15      |                              ^~~~~~~~~~~~
   16/home/hebasto/dev/bitcoin/depends/work/build/x86_64-unknown-netbsd10.0/libevent/2.1.12-stable-ca6b96ec97c/kqueue.c:56:27: error: called object is not a function or function pointer
   17   56 | #define INT_TO_UDATA(x) ((typeof(((struct kevent *)0)->udata))(intptr_t)(x))
   18      |                          ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   19/home/hebasto/dev/bitcoin/depends/work/build/x86_64-unknown-netbsd10.0/libevent/2.1.12-stable-ca6b96ec97c/kqueue.c:190:30: note: in expansion of macro 'INT_TO_UDATA'
   20  190 |                 out->udata = INT_TO_UDATA(ADD_UDATA);
   21      |                              ^~~~~~~~~~~~
   22gmake[3]: *** [CMakeFiles/event_core_static.dir/build.make:328: CMakeFiles/event_core_static.dir/kqueue.c.o] Error 1
   23<snip>
   

   This PR resolves this issue by following GCC’s recommendation:

   write __typeof__ instead of typeof.

2. depends: Fix compiling `libevent` package on NetBSD 53ae319eee
3. hebasto added the label Build system on Dec 14, 2024
4. 
   DrahtBot commented at 3:41 pm on December 14, 2024: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

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   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/31500.

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5. 
   fanquake commented at 10:55 am on December 17, 2024: member

   Can you link to the upstream issue / PR.
6. 
   theuni commented at 5:08 pm on December 19, 2024: member

   LGTM, but yeah, it’d be helpful to upstream this.

   FWIW c23 adds typeof(), so technically guards for that could be added. Not worth the complexity though.

7. 
   hebasto commented at 4:08 pm on December 20, 2024: member

   Can you link to the upstream issue / PR.

   LGTM, but yeah, it’d be helpful to upstream this.

   Sure thing!

   Here is an upstream PR: https://github.com/libevent/libevent/pull/1768.

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hebasto DrahtBot fanquake theuni

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