From: "Jose E. Marchesi" <jose.marchesi@oracle.com>
To: "WanLi Niu" <kiraskyler@163.com>
Cc: Quentin Monnet <qmo@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Menglong Dong <menglong8.dong@gmail.com>, <bpf@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
WanLi Niu <niuwl1@chinatelecom.cn>,
Menglong Dong <dongml2@chinatelecom.cn>
Subject: Re: [PATCH v4 bpf-next] bpftool: Make skeleton C++ compatible with explicit casts
Date: Mon, 05 Jan 2026 17:05:53 +0100 [thread overview]
Message-ID: <87seckf3j2.fsf@oracle.com> (raw)
In-Reply-To: <7219135.9fee.19b8e385eb5.Coremail.kiraskyler@163.com>
>> FWIW I tested the reproducer with gcc-bpf and got no pointer conversion
>> warnings (not that I was expecting anything different, but just in
>> case):
>>
>> $ bpf-unknown-none-gcc -std=gnu11 -I./tools/include -g -O2 -c text.bpf.c -o test.bpf.o
>> $ bpftool gen skeleton test.bpf.o -L > test.bpf.skel.h
>> $ g++ -c test.cpp -I.
>
> Thanks for testing.
>
> The issue only occurs when bpftool gen skeleton is used in use_loader
> mode (bpftool gen skeleton -L|--use-loader).
>
> Could you double-check if -L was included? I can reproduce the error
> reliably with it — here’s the full output:
I meant to say that I tested the reproducer _with your patch applied_.
It indeed cures the issue :)
Sorry it wasn't clear.
>
> $ rpm -qf `which bpf-unknown-none-gcc`
> gcc-bpf-unknown-none-15.2.1-1.fc42.x86_64
> $ bpf-unknown-none-gcc -std=gnu11 -I/usr/include -g -O2 -c test.bpf.c -o test.bpf.o
> $ bpftool gen skeleton test.bpf.o -L > test.bpf.skel.h
> libbpf: elf: skipping section(2) .data (size 0)
> libbpf: elf: skipping unrecognized data section(7) .comment
> libbpf: prog 'handle': missing .BTF.ext line info for the main program, skipping all of .BTF.ext line info.
> $ g++ -c test.cpp -I.
> In file included from test.cpp:4:
> test.bpf.skel.h: In function ‘test_bpf* test_bpf__open()’:
> test.bpf.skel.h:65:26: error: invalid conversion from ‘void*’ to ‘test_bpf*’ [-fpermissive]
> 65 | skel = skel_alloc(sizeof(*skel));
> | ~~~~~~~~~~^~~~~~~~~~~~~~~
> | |
> | void*
> test.bpf.skel.h:68:55: error: invalid use of ‘void’
> 68 | skel->ctx.sz = (void *)&skel->links - (void *)skel;
> | ^~~~
> test.bpf.skel.h:73:47: error: invalid conversion from ‘void*’ to ‘test_bpf::test_bpf__bss*’ [-fpermissive]
> 73 | skel->bss = skel_prep_map_data((void *)data, 4096,
> | ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
> | |
> | void*
> 74 | sizeof(data) - 1);
> | ~~~~~~~~~~~~~~~~~
> test.bpf.skel.h: In function ‘int test_bpf__load(test_bpf*)’:
> test.bpf.skel.h:196:43: error: invalid conversion from ‘void*’ to ‘test_bpf::test_bpf__bss*’ [-fpermissive]
> 196 | skel->bss = skel_finalize_map_data(&skel->maps.bss.initial_value,
> | ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> | |
> | void*
> 197 | 4096, PROT_READ | PROT_WRITE, skel->maps.bss.map_fd);
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> $ cat test.bpf.skel.h
> /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
> /* THIS FILE IS AUTOGENERATED BY BPFTOOL! */
> #ifndef __TEST_BPF_SKEL_H__
> #define __TEST_BPF_SKEL_H__
>
> #include <bpf/skel_internal.h>
>
> struct test_bpf {
> struct bpf_loader_ctx ctx;
> struct {
> struct bpf_map_desc bss;
> } maps;
> struct {
> struct bpf_prog_desc handle;
> } progs;
> struct {
> int handle_fd;
> } links;
> struct test_bpf__bss {
> int val;
> } *bss;
> };
>
> static inline int
> test_bpf__handle__attach(struct test_bpf *skel)
> {
> int prog_fd = skel->progs.handle.prog_fd;
> int fd = skel_raw_tracepoint_open("sched_wakeup_new", prog_fd);
>
> if (fd > 0)
> skel->links.handle_fd = fd;
> return fd;
> }
>
> static inline int
> test_bpf__attach(struct test_bpf *skel)
> {
> int ret = 0;
>
> ret = ret < 0 ? ret : test_bpf__handle__attach(skel);
> return ret < 0 ? ret : 0;
> }
>
> static inline void
> test_bpf__detach(struct test_bpf *skel)
> {
> skel_closenz(skel->links.handle_fd);
> }
> static void
> test_bpf__destroy(struct test_bpf *skel)
> {
> if (!skel)
> return;
> test_bpf__detach(skel);
> skel_closenz(skel->progs.handle.prog_fd);
> skel_free_map_data(skel->bss, skel->maps.bss.initial_value, 4096);
> skel_closenz(skel->maps.bss.map_fd);
> skel_free(skel);
> }
> static inline struct test_bpf *
> test_bpf__open(void)
> {
> struct test_bpf *skel;
>
> skel = skel_alloc(sizeof(*skel));
> if (!skel)
> goto cleanup;
> skel->ctx.sz = (void *)&skel->links - (void *)skel;
> {
> static const char data[] __attribute__((__aligned__(8))) = "\
> \0\0\0\0";
>
> skel->bss = skel_prep_map_data((void *)data, 4096,
> sizeof(data) - 1);
> if (!skel->bss)
> goto cleanup;
> skel->maps.bss.initial_value = (__u64) (long) skel->bss;
> }
> return skel;
> cleanup:
> test_bpf__destroy(skel);
> return NULL;
> }
>
> static inline int
> test_bpf__load(struct test_bpf *skel)
> {
> struct bpf_load_and_run_opts opts = {};
> int err;
> static const char opts_data[] __attribute__((__aligned__(8))) = "\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x9f\xeb\x01\0\
> \x18\0\0\0\0\0\0\0\x64\0\0\0\x64\0\0\0\x41\0\0\0\0\0\0\0\x01\0\0\x0d\x02\0\0\0\
> \x18\0\0\0\x03\0\0\0\x08\0\0\0\0\0\0\x01\x04\0\0\0\x20\0\0\x01\0\0\0\0\0\0\0\
> \x02\0\0\0\0\x13\0\0\0\0\0\0\x0e\x02\0\0\0\x01\0\0\0\x0c\0\0\0\x01\0\0\x0c\x01\
> \0\0\0\x3c\0\0\0\x01\0\0\x0f\x04\0\0\0\x04\0\0\0\0\0\0\0\x04\0\0\0\0\x68\x61\
> \x6e\x64\x6c\x65\0\x69\x6e\x74\0\x68\x61\x6e\x64\x6c\x65\0\x76\x61\x6c\0\0\x63\
> \x74\x78\0\x72\x61\x77\x5f\x74\x72\x61\x63\x65\x70\x6f\x69\x6e\x74\x2f\x73\x63\
> \x68\x65\x64\x5f\x77\x61\x6b\x65\x75\x70\x5f\x6e\x65\x77\0\x2e\x62\x73\x73\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\xbd\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x02\0\0\
> \0\x04\0\0\0\x04\0\0\0\x01\0\0\0\0\x04\0\0\0\0\0\0\0\0\0\0\x74\x65\x73\x74\x5f\
> \x62\x70\x66\x2e\x62\x73\x73\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x06\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\xb7\0\0\0\0\0\0\0\x95\0\0\0\
> \0\0\0\0\0\0\0\0\x05\0\0\0\x11\0\0\0\x02\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x68\x61\x6e\x64\x6c\x65\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x08\0\0\0\0\0\0\0\0\0\0\0\x01\0\0\0\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\
> \0\0\0\x10\0\0\0\0\0\0\0";
> static const char opts_insn[] __attribute__((__aligned__(8))) = "\
> \xbf\x16\0\0\0\0\0\0\xbf\xa1\0\0\0\0\0\0\x07\x01\0\0\x78\xff\xff\xff\xb7\x02\0\
> \0\x88\0\0\0\xb7\x03\0\0\0\0\0\0\x85\0\0\0\x71\0\0\0\x05\0\x11\0\0\0\0\0\x61\
> \xa1\x78\xff\0\0\0\0\xd5\x01\x01\0\0\0\0\0\x85\0\0\0\xa8\0\0\0\x61\xa1\x7c\xff\
> \0\0\0\0\xd5\x01\x01\0\0\0\0\0\x85\0\0\0\xa8\0\0\0\x61\xa1\x80\xff\0\0\0\0\xd5\
> \x01\x01\0\0\0\0\0\x85\0\0\0\xa8\0\0\0\x18\x60\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x61\
> \x01\0\0\0\0\0\0\xd5\x01\x02\0\0\0\0\0\xbf\x19\0\0\0\0\0\0\x85\0\0\0\xa8\0\0\0\
> \xbf\x70\0\0\0\0\0\0\x95\0\0\0\0\0\0\0\x61\x60\x08\0\0\0\0\0\x18\x61\0\0\0\0\0\
> \0\0\0\0\0\xd8\x05\0\0\x63\x01\0\0\0\0\0\0\x61\x60\x0c\0\0\0\0\0\x18\x61\0\0\0\
> \0\0\0\0\0\0\0\xd4\x05\0\0\x63\x01\0\0\0\0\0\0\x79\x60\x10\0\0\0\0\0\x18\x61\0\
> \0\0\0\0\0\0\0\0\0\xc8\x05\0\0\x7b\x01\0\0\0\0\0\0\x18\x60\0\0\0\0\0\0\0\0\0\0\
> \0\x05\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\xc0\x05\0\0\x7b\x01\0\0\0\0\0\0\xb7\x01\
> \0\0\x12\0\0\0\x18\x62\0\0\0\0\0\0\0\0\0\0\xc0\x05\0\0\xb7\x03\0\0\x1c\0\0\0\
> \x85\0\0\0\xa6\0\0\0\xbf\x07\0\0\0\0\0\0\xc5\x07\xd7\xff\0\0\0\0\x63\x7a\x78\
> \xff\0\0\0\0\x61\xa0\x78\xff\0\0\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\x10\x06\0\0\
> \x63\x01\0\0\0\0\0\0\x61\x60\x1c\0\0\0\0\0\x15\0\x03\0\0\0\0\0\x18\x61\0\0\0\0\
> \0\0\0\0\0\0\xec\x05\0\0\x63\x01\0\0\0\0\0\0\xb7\x01\0\0\0\0\0\0\x18\x62\0\0\0\
> \0\0\0\0\0\0\0\xe0\x05\0\0\xb7\x03\0\0\x48\0\0\0\x85\0\0\0\xa6\0\0\0\xbf\x07\0\
> \0\0\0\0\0\xc5\x07\xc6\xff\0\0\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x63\x71\
> \0\0\0\0\0\0\x79\x63\x20\0\0\0\0\0\x15\x03\x08\0\0\0\0\0\x18\x61\0\0\0\0\0\0\0\
> \0\0\0\x28\x06\0\0\xb7\x02\0\0\x04\0\0\0\x61\x60\x04\0\0\0\0\0\x45\0\x02\0\x01\
> \0\0\0\x85\0\0\0\x94\0\0\0\x05\0\x01\0\0\0\0\0\x85\0\0\0\x71\0\0\0\x18\x62\0\0\
> \0\0\0\0\0\0\0\0\0\0\0\0\x61\x20\0\0\0\0\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\x38\
> \x06\0\0\x63\x01\0\0\0\0\0\0\x18\x60\0\0\0\0\0\0\0\0\0\0\x30\x06\0\0\x18\x61\0\
> \0\0\0\0\0\0\0\0\0\x40\x06\0\0\x7b\x01\0\0\0\0\0\0\x18\x60\0\0\0\0\0\0\0\0\0\0\
> \x28\x06\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\x48\x06\0\0\x7b\x01\0\0\0\0\0\0\xb7\
> \x01\0\0\x02\0\0\0\x18\x62\0\0\0\0\0\0\0\0\0\0\x38\x06\0\0\xb7\x03\0\0\x20\0\0\
> \0\x85\0\0\0\xa6\0\0\0\xbf\x07\0\0\0\0\0\0\xc5\x07\xa2\xff\0\0\0\0\x18\x60\0\0\
> \0\0\0\0\0\0\0\0\x58\x06\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\x88\x06\0\0\x7b\x01\0\
> \0\0\0\0\0\x18\x60\0\0\0\0\0\0\0\0\0\0\x60\x06\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\
> \x80\x06\0\0\x7b\x01\0\0\0\0\0\0\x18\x60\0\0\0\0\0\0\0\0\0\0\x70\x06\0\0\x18\
> \x61\0\0\0\0\0\0\0\0\0\0\xc8\x06\0\0\x7b\x01\0\0\0\0\0\0\x18\x60\0\0\0\0\0\0\0\
> \0\0\0\x78\x06\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\xd8\x06\0\0\x7b\x01\0\0\0\0\0\0\
> \x18\x60\0\0\0\0\0\0\0\0\0\0\x78\x06\0\0\x18\x61\0\0\0\0\0\0\0\0\0\0\xf8\x06\0\
> \0\x7b\x01\0\0\0\0\0\0\x18\x60\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x18\x61\0\0\0\0\0\0\
> \0\0\0\0\xf0\x06\0\0\x7b\x01\0\0\0\0\0\0\x61\x60\x08\0\0\0\0\0\x18\x61\0\0\0\0\
> \0\0\0\0\0\0\x90\x06\0\0\x63\x01\0\0\0\0\0\0\x61\x60\x0c\0\0\0\0\0\x18\x61\0\0\
> \0\0\0\0\0\0\0\0\x94\x06\0\0\x63\x01\0\0\0\0\0\0\x79\x60\x10\0\0\0\0\0\x18\x61\
> \0\0\0\0\0\0\0\0\0\0\x98\x06\0\0\x7b\x01\0\0\0\0\0\0\x61\xa0\x78\xff\0\0\0\0\
> \x18\x61\0\0\0\0\0\0\0\0\0\0\xc0\x06\0\0\x63\x01\0\0\0\0\0\0\xb7\x01\0\0\x05\0\
> \0\0\x18\x62\0\0\0\0\0\0\0\0\0\0\x78\x06\0\0\xb7\x03\0\0\x8c\0\0\0\x85\0\0\0\
> \xa6\0\0\0\xbf\x07\0\0\0\0\0\0\xc5\x07\x6d\xff\0\0\0\0\x63\x7a\x80\xff\0\0\0\0\
> \x61\xa1\x78\xff\0\0\0\0\xd5\x01\x02\0\0\0\0\0\xbf\x19\0\0\0\0\0\0\x85\0\0\0\
> \xa8\0\0\0\x61\xa0\x80\xff\0\0\0\0\x63\x06\x28\0\0\0\0\0\x18\x61\0\0\0\0\0\0\0\
> \0\0\0\0\0\0\0\x61\x10\0\0\0\0\0\0\x63\x06\x18\0\0\0\0\0\xb7\0\0\0\0\0\0\0\x95\
> \0\0\0\0\0\0\0";
> opts.ctx = (struct bpf_loader_ctx *)skel;
> opts.data_sz = sizeof(opts_data) - 1;
> opts.data = (void *)opts_data;
> opts.insns_sz = sizeof(opts_insn) - 1;
> opts.insns = (void *)opts_insn;
>
> err = bpf_load_and_run(&opts);
> if (err < 0)
> return err;
> skel->bss = skel_finalize_map_data(&skel->maps.bss.initial_value,
> 4096, PROT_READ | PROT_WRITE, skel->maps.bss.map_fd);
> if (!skel->bss)
> return -ENOMEM;
> return 0;
> }
>
> static inline struct test_bpf *
> test_bpf__open_and_load(void)
> {
> struct test_bpf *skel;
>
> skel = test_bpf__open();
> if (!skel)
> return NULL;
> if (test_bpf__load(skel)) {
> test_bpf__destroy(skel);
> return NULL;
> }
> return skel;
> }
>
> __attribute__((unused)) static void
> test_bpf__assert(struct test_bpf *s __attribute__((unused)))
> {
> #ifdef __cplusplus
> #define _Static_assert static_assert
> #endif
> _Static_assert(sizeof(s->bss->val) == 4, "unexpected size of 'val'");
> #ifdef __cplusplus
> #undef _Static_assert
> #endif
> }
>
> #endif /* __TEST_BPF_SKEL_H__ */
>
> At 2026-01-05 19:50:25, "Jose E. Marchesi" <jose.marchesi@oracle.com> wrote:
>>
>>FWIW I tested the reproducer with gcc-bpf and got no pointer conversion
>>warnings (not that I was expecting anything different, but just in
>>case):
>>
>> $ bpf-unknown-none-gcc -std=gnu11 -I./tools/include -g -O2 -c text.bpf.c -o test.bpf.o
>> $ bpftool gen skeleton test.bpf.o -L > test.bpf.skel.h
>> $ g++ -c test.cpp -I.
>>
>>> From: WanLi Niu <niuwl1@chinatelecom.cn>
>>>
>>> Fix C++ compilation errors in generated skeleton by adding explicit
>>> pointer casts and using integer subtraction for offset calculation.
>>>
>>> Use struct outer::inner syntax under __cplusplus to access nested skeleton map
>>> structs, ensuring C++ compilation compatibility while preserving C support
>>>
>>> error: invalid conversion from 'void*' to '<obj_name>*' [-fpermissive]
>>> | skel = skel_alloc(sizeof(*skel));
>>> | ~~~~~~~~~~^~~~~~~~~~~~~~~
>>> | |
>>> | void*
>>>
>>> error: arithmetic on pointers to void
>>> | skel->ctx.sz = (void *)&skel->links - (void *)skel;
>>> | ~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~
>>>
>>> error: assigning to 'struct <obj_name>__<ident> *' from incompatible type 'void *'
>>> | skel-><ident> = skel_prep_map_data((void *)data, 4096,
>>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> | sizeof(data) - 1);
>>> | ~~~~~~~~~~~~~~~~~
>>>
>>> error: assigning to 'struct <obj_name>__<ident> *' from incompatible type 'void *'
>>> | skel-><ident> = skel_finalize_map_data(&skel->maps.<ident>.initial_value,
>>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> | 4096, PROT_READ | PROT_WRITE, skel->maps.<ident>.map_fd);
>>> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> Minimum reproducer:
>>>
>>> $ cat test.bpf.c
>>> int val; // placed in .bss section
>>>
>>> #include "vmlinux.h"
>>> #include <bpf/bpf_helpers.h>
>>>
>>> SEC("raw_tracepoint/sched_wakeup_new") int handle(void *ctx) { return 0; }
>>>
>>> $ cat test.cpp
>>> #include <cerrno>
>>>
>>> extern "C" {
>>> #include "test.bpf.skel.h"
>>> }
>>>
>>> $ bpftool btf dump file /sys/kernel/btf/vmlinux format c > vmlinux.h
>>> $ clang -g -O2 -target bpf -c test.bpf.c -o test.bpf.o
>>> $ bpftool gen skeleton test.bpf.o -L > test.bpf.skel.h
>>> $ g++ -c test.cpp -I.
>>>
>>> Signed-off-by: WanLi Niu <niuwl1@chinatelecom.cn>
>>> Co-developed-by: Menglong Dong <dongml2@chinatelecom.cn>
>>> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
>>> ---
>>> changelog:
>>> v4:
>>> - Add a minimum reproducer to demonstrate the issue, as suggested by Yonghong Song
>>>
>>> v3: https://lore.kernel.org/all/20260104021402.2968-1-kiraskyler@163.com/
>>> - Fix two additional <obj_name>__<ident> type mismatches as suggested by Yonghong Song
>>>
>>> v2: https://lore.kernel.org/all/20251231102929.3843-1-kiraskyler@163.com/
>>> - Use generic (struct %1$s *) instead of project-specific (struct trace_bpf *)
>>>
>>> v1: https://lore.kernel.org/all/20251231092541.3352-1-kiraskyler@163.com/
>>> ---
>>> tools/bpf/bpftool/gen.c | 16 ++++++++++++----
>>> 1 file changed, 12 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
>>> index 993c7d9484a4..010861b7d0ea 100644
>>> --- a/tools/bpf/bpftool/gen.c
>>> +++ b/tools/bpf/bpftool/gen.c
>>> @@ -731,10 +731,10 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
>>> { \n\
>>> struct %1$s *skel; \n\
>>> \n\
>>> - skel = skel_alloc(sizeof(*skel)); \n\
>>> + skel = (struct %1$s *)skel_alloc(sizeof(*skel)); \n\
>>> if (!skel) \n\
>>> goto cleanup; \n\
>>> - skel->ctx.sz = (void *)&skel->links - (void *)skel; \n\
>>> + skel->ctx.sz = (__u64)&skel->links - (__u64)skel; \n\
>>> ",
>>> obj_name, opts.data_sz);
>>> bpf_object__for_each_map(map, obj) {
>>> @@ -755,13 +755,17 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
>>> \n\
>>> \"; \n\
>>> \n\
>>> + #ifdef __cplusplus \n\
>>> + skel->%1$s = (struct %3$s::%3$s__%1$s *)skel_prep_map_data((void *)data, %2$zd,\n\
>>> + #else \n\
>>> skel->%1$s = skel_prep_map_data((void *)data, %2$zd,\n\
>>> + #endif \n\
>>> sizeof(data) - 1);\n\
>>> if (!skel->%1$s) \n\
>>> goto cleanup; \n\
>>> skel->maps.%1$s.initial_value = (__u64) (long) skel->%1$s;\n\
>>> } \n\
>>> - ", ident, bpf_map_mmap_sz(map));
>>> + ", ident, bpf_map_mmap_sz(map), obj_name);
>>> }
>>> codegen("\
>>> \n\
>>> @@ -857,12 +861,16 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
>>>
>>> codegen("\
>>> \n\
>>> + #ifdef __cplusplus \n\
>>> + skel->%1$s = (struct %4$s::%4$s__%1$s *)skel_finalize_map_data(&skel->maps.%1$s.initial_value,\n\
>>> + #else \n\
>>> skel->%1$s = skel_finalize_map_data(&skel->maps.%1$s.initial_value, \n\
>>> + #endif \n\
>>> %2$zd, %3$s, skel->maps.%1$s.map_fd);\n\
>>> if (!skel->%1$s) \n\
>>> return -ENOMEM; \n\
>>> ",
>>> - ident, bpf_map_mmap_sz(map), mmap_flags);
>>> + ident, bpf_map_mmap_sz(map), mmap_flags, obj_name);
>>> }
>>> codegen("\
>>> \n\
next prev parent reply other threads:[~2026-01-05 16:07 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-31 9:25 [PATCH bpf-next] bpftool: Make skeleton C++ compatible with explicit casts WanLi Niu
2025-12-31 9:48 ` bot+bpf-ci
2025-12-31 10:29 ` [PATCH v2 " WanLi Niu
2026-01-02 19:35 ` Yonghong Song
2026-01-04 2:14 ` [PATCH v3 " WanLi Niu
2026-01-05 5:27 ` Yonghong Song
2026-01-05 7:12 ` [PATCH v4 " WanLi Niu
2026-01-05 10:39 ` Quentin Monnet
2026-01-05 11:50 ` Jose E. Marchesi
2026-01-05 12:53 ` WanLi Niu
2026-01-05 16:05 ` Jose E. Marchesi [this message]
2026-01-06 2:31 ` [PATCH v5 " WanLi Niu
2026-01-09 19:00 ` patchwork-bot+netdevbpf
2026-01-06 0:46 ` [PATCH v3 " Andrii Nakryiko
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