tools/bpf/bpftool/gen.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
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);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:
v3:
- 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\
--
2.39.1On Sat, Jan 3, 2026 at 6:15 PM WanLi Niu <kiraskyler@163.com> wrote:
>
> 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);
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> 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:
> v3:
> - 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$s *)skel_alloc(sizeof(*skel)); \n\
> if (!skel) \n\
> goto cleanup; \n\
> - skel->ctx.sz = (void *)&skel->links - (void *)skel; \n\
> + skel->ctx.sz = (__u64)&skel->links - (__u64)skel; \n\
I'm wondering if this can also trigger some warnings under some
circumstances? void * is castable to long or unsigned long, but __u64
can be defined as long long (plus it's a question what happens on
32-bit architectures). Why worry about this if we can cast to `char *`
to calculate this size?
> ",
> obj_name, opts.data_sz);
> bpf_object__for_each_map(map, obj) {
> @@ -755,13 +755,17 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
> \n\
> \"; \n\
> \n\
> + #ifdef __cplusplus \n\
> + skel->%1$s = (struct %3$s::%3$s__%1$s *)skel_prep_map_data((void *)data, %2$zd,\n\
we already use __typeof__() (see gen_st_ops_shadow_init), so let's use
that unconditionally without __cplusplus special casing
pw-bot: cr
> + #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\
same as above, __typeof__ ?
> + #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\
> --
> 2.39.1
>
On 1/3/26 6:14 PM, WanLi Niu wrote: > 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); > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Signed-off-by: WanLi Niu <niuwl1@chinatelecom.cn> > Co-developed-by: Menglong Dong <dongml2@chinatelecom.cn> > Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn> LGTM. Could you add a minimum reproducer in the commit message? Acked-by: Yonghong Song <yonghong.song@linux.dev>
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\
--
2.39.1
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\
> 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:
$ 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))) = "\
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\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\
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\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\
>> 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\
On 05/01/2026 07:12, WanLi Niu wrote:
> 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.
I tried it and could confirm that the warnings are gone.
> Signed-off-by: WanLi Niu <niuwl1@chinatelecom.cn>
> Co-developed-by: Menglong Dong <dongml2@chinatelecom.cn>
> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Acked-by: Quentin Monnet <qmo@kernel.org>
Thank you!
From: WanLi Niu <niuwl1@chinatelecom.cn>
Fix C++ compilation errors in generated skeleton by adding explicit
pointer casts and use char * subtraction for offset calculation
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:
v5:
- Use char * arithmetic instead of integer subtraction for offsets as suggested by Andrii Nakryiko
- Use __typeof__() without __cplusplus special casing as suggested by Andrii Nakryiko
v4: https://lore.kernel.org/all/20260105071231.2501-1-kiraskyler@163.com/
- 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$s *) instead of project-specific (struct trace_bpf *)
v1: https://lore.kernel.org/all/20251231092541.3352-1-kiraskyler@163.com/
---
tools/bpf/bpftool/gen.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 993c7d9484a4..2f9e10752e28 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -731,10 +731,10 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
{ \n\
struct %1$s *skel; \n\
\n\
- skel = skel_alloc(sizeof(*skel)); \n\
+ skel = (struct %1$s *)skel_alloc(sizeof(*skel)); \n\
if (!skel) \n\
goto cleanup; \n\
- skel->ctx.sz = (void *)&skel->links - (void *)skel; \n\
+ skel->ctx.sz = (char *)&skel->links - (char *)skel; \n\
",
obj_name, opts.data_sz);
bpf_object__for_each_map(map, obj) {
@@ -755,7 +755,7 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
\n\
\"; \n\
\n\
- skel->%1$s = skel_prep_map_data((void *)data, %2$zd,\n\
+ skel->%1$s = (__typeof__(skel->%1$s))skel_prep_map_data((void *)data, %2$zd,\n\
sizeof(data) - 1);\n\
if (!skel->%1$s) \n\
goto cleanup; \n\
@@ -857,7 +857,7 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
codegen("\
\n\
- skel->%1$s = skel_finalize_map_data(&skel->maps.%1$s.initial_value, \n\
+ skel->%1$s = (__typeof__(skel->%1$s))skel_finalize_map_data(&skel->maps.%1$s.initial_value,\n\
%2$zd, %3$s, skel->maps.%1$s.map_fd);\n\
if (!skel->%1$s) \n\
return -ENOMEM; \n\
--
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