Messages in this thread Patch in this message | | | Date | Wed, 28 Dec 2022 10:42:37 -0800 | Subject | Re: [PATCH bpf-next] selftests/bpf: move struct definitions out of function params | From | Yonghong Song <> |
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On 12/22/22 11:26 AM, James Hilliard wrote: > On Thu, Dec 22, 2022 at 12:04 PM Andrii Nakryiko > <andrii.nakryiko@gmail.com> wrote: >> >> On Tue, Dec 20, 2022 at 9:59 PM James Hilliard >> <james.hilliard1@gmail.com> wrote: >>> >>> Anonymous structs can't be declared inside function parameter >>> definitions in current c standards, however clang doesn't detect this >>> condition currently while GCC does. >>> >>> Details: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108189 >>> >>> Fixes errors like: >>> progs/btf_dump_test_case_bitfields.c:85:7: error: anonymous struct declared inside parameter list will not be visible outside of this definition or declaration [-Werror] >>> 85 | int f(struct { >>> | ^~~~~~ >>> >>> Signed-off-by: James Hilliard <james.hilliard1@gmail.com> >>> --- >>> .../bpf/progs/btf_dump_test_case_bitfields.c | 9 ++++-- >>> .../progs/btf_dump_test_case_namespacing.c | 10 ++++--- >>> .../bpf/progs/btf_dump_test_case_packing.c | 10 ++++--- >>> .../bpf/progs/btf_dump_test_case_padding.c | 10 ++++--- >>> .../bpf/progs/btf_dump_test_case_syntax.c | 30 +++++++++++++------ >>> 5 files changed, 46 insertions(+), 23 deletions(-) >>> >>> diff --git a/tools/testing/selftests/bpf/progs/btf_dump_test_case_bitfields.c b/tools/testing/selftests/bpf/progs/btf_dump_test_case_bitfields.c >>> index e01690618e1e..c75f6bd06a49 100644 >>> --- a/tools/testing/selftests/bpf/progs/btf_dump_test_case_bitfields.c >>> +++ b/tools/testing/selftests/bpf/progs/btf_dump_test_case_bitfields.c >>> @@ -82,11 +82,16 @@ struct bitfield_flushed { >>> long b: 16; >>> }; >>> >>> -int f(struct { >>> +/* ----- START-EXPECTED-OUTPUT ----- */ >>> +struct root_struct { >> >> there is no need to make this struct part of expected output, just >> keep it next to f? > > Seems to be required as the diff check fails otherwise. > >> >> >>> struct bitfields_only_mixed_types _1; >>> struct bitfield_mixed_with_others _2; >>> struct bitfield_flushed _3; >>> -} *_) >>> +}; >>> + >>> +/* ------ END-EXPECTED-OUTPUT ------ */ >>> + >>> +int f(struct root_struct *_) >>> { >>> return 0; >>> } >>> diff --git a/tools/testing/selftests/bpf/progs/btf_dump_test_case_namespacing.c b/tools/testing/selftests/bpf/progs/btf_dump_test_case_namespacing.c >>> index 92a4ad428710..d7cf2a8487c9 100644 >>> --- a/tools/testing/selftests/bpf/progs/btf_dump_test_case_namespacing.c >>> +++ b/tools/testing/selftests/bpf/progs/btf_dump_test_case_namespacing.c >>> @@ -49,9 +49,7 @@ typedef int Y; >>> >>> typedef int Z; >>> >>> -/*------ END-EXPECTED-OUTPUT ------ */ >>> - >>> -int f(struct { >>> +struct root_struct { >>> struct S _1; >>> S _2; >>> union U _3; >>> @@ -67,7 +65,11 @@ int f(struct { >>> X xx; >>> Y yy; >>> Z zz; >>> -} *_) >>> +}; >> >> same, that struct is only to preserve all the referenced types, so >> keep it hidden from the output > > I wasn't able to find a way to keep it out of the output. > > The other tests with a root_struct seem to always have it in the output: > https://github.com/torvalds/linux/blob/v6.1/tools/testing/selftests/bpf/progs/btf_dump_test_case_multidim.c#L21-L28 > https://github.com/torvalds/linux/blob/v6.1/tools/testing/selftests/bpf/progs/btf_dump_test_case_ordering.c#L50-L56 > https://github.com/torvalds/linux/blob/v6.1/tools/testing/selftests/bpf/progs/btf_dump_test_case_syntax.c#L222-L237 > >> >>> + >>> +/*------ END-EXPECTED-OUTPUT ------ */ >>> + >>> +int f(struct root_struct *_) >>> { >>> return 0; >>> } >>> diff --git a/tools/testing/selftests/bpf/progs/btf_dump_test_case_packing.c b/tools/testing/selftests/bpf/progs/btf_dump_test_case_packing.c >>> index 7998f27df7dd..e039ceb50c43 100644 >>> --- a/tools/testing/selftests/bpf/progs/btf_dump_test_case_packing.c >>> +++ b/tools/testing/selftests/bpf/progs/btf_dump_test_case_packing.c >>> @@ -132,9 +132,7 @@ struct outer_packed_struct { >>> struct nested_packed_struct b; >>> } __attribute__((packed)); >>> >>> -/* ------ END-EXPECTED-OUTPUT ------ */ >>> - >>> -int f(struct { >>> +struct root_struct { >>> struct packed_trailing_space _1; >>> struct non_packed_trailing_space _2; >>> struct packed_fields _3; >>> @@ -147,7 +145,11 @@ int f(struct { >>> struct usb_host_endpoint _10; >>> struct outer_nonpacked_struct _11; >>> struct outer_packed_struct _12; >>> -} *_) >>> +}; >>> + >>> +/* ------ END-EXPECTED-OUTPUT ------ */ >>> + >>> +int f(struct root_struct *_) >>> { >>> return 0; >>> } >>> diff --git a/tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c b/tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c >>> index 79276fbe454a..2ca46ad8d66a 100644 >>> --- a/tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c >>> +++ b/tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c >>> @@ -220,9 +220,7 @@ struct outer_mixed_but_unpacked { >>> struct nested_packed b2; >>> }; >>> >>> -/* ------ END-EXPECTED-OUTPUT ------ */ >>> - >>> -int f(struct { >>> +struct root_struct { >>> struct padded_implicitly _1; >>> struct padded_explicitly _2; >>> struct padded_a_lot _3; >>> @@ -243,7 +241,11 @@ int f(struct { >>> struct ib_wc _201; >>> struct acpi_object_method _202; >>> struct outer_mixed_but_unpacked _203; >>> -} *_) >>> +} __attribute__((packed)); >>> + >>> +/* ------ END-EXPECTED-OUTPUT ------ */ >>> + >>> +int f(struct root_struct *_) >>> { >>> return 0; >>> } >>> diff --git a/tools/testing/selftests/bpf/progs/btf_dump_test_case_syntax.c b/tools/testing/selftests/bpf/progs/btf_dump_test_case_syntax.c >>> index 26fffb02ed10..3e31df7cecc6 100644 >>> --- a/tools/testing/selftests/bpf/progs/btf_dump_test_case_syntax.c >>> +++ b/tools/testing/selftests/bpf/progs/btf_dump_test_case_syntax.c >>> @@ -104,24 +104,24 @@ typedef void (*printf_fn_t)(const char *, ...); >>> * typedef const fn_output_inner_t fn_ptr_arr2_t[5]; >>> */ >>> /* ----- START-EXPECTED-OUTPUT ----- */ >>> -typedef char * const * (*fn_ptr2_t)(struct { >>> - int a; >>> -}, int (*)(int)); >>> +struct struct_a; >>> + >>> +typedef char * const * (*fn_ptr2_t)(struct struct_a, int (*)(int)); >>> + >>> +struct struct_c; >>> + >>> +struct struct_h; >>> >>> typedef struct { >>> int a; >>> - void (*b)(int, struct { >>> - int c; >>> - }, union { >>> + void (*b)(int, struct struct_c, union { >>> char d; >>> int e[5]; >>> }); >>> } (*fn_complex_t)(union { >>> void *f; >>> char g[16]; >>> -}, struct { >>> - int h; >>> -}); >>> +}, struct struct_h); >> >> these do test some pieces of libbpf's btf_dump logic, so I'm way more >> reluctant to remove these. If I understand correctly, this syntax will >> be eventually supported by GCC, so is there any way to keep these >> examples as is by requiring C23 mode or something? Or just skipping >> compiling this one if GCC is used? > > I'm not sure, I'm having trouble finding a description in the C23 specification, > I presume if it is in there then GCC will eventually support it. > > Maybe just keep the root_struct changes for now and hold off on this until > it's clarified that this is valid C23 code or not? > > At the moment it appears there's a clang bug here as it shouldn't be valid > C17 code(which AFAIU is clang's default).
Looks like clang supports anonymous struct parameter all the way back to c89. I tried clang12 and latest clang16.
$ cat t.c typedef char * const * (*fn_ptr2_t)(struct { int a; }, int (*)(int)); fn_ptr2_t h; $ clang -S -emit-llvm -g -std=c89 t.c $ clang -S -emit-llvm -g -std=c11 t.c $ clang -S -emit-llvm -g -std=c17 t.c ]$ clang -S -emit-llvm -g t.c $ gcc -v -S t.c ... GNU C17 (GCC) version 8.5.0 20210514 (Red Hat 8.5.0-17) (x86_64-redhat-linux) ... t.c:1:37: warning: anonymous struct declared inside parameter list will not be visible outside of this definition or declaration typedef char * const * (*fn_ptr2_t)(struct { ^~~~~~ ...
I agree that we should understand better about standard requirement before making the change.
> >> >>> >>> typedef void (* (*signal_t)(int, void (*)(int)))(int); >>> >>> @@ -272,6 +272,18 @@ struct root_struct { >>> struct float_struct _15; >>> }; >>> >>> +struct struct_a { >>> + int a; >>> +}; >>> + >>> +struct struct_h { >>> + int h; >>> +}; >>> + >>> +struct struct_c { >>> + int c; >>> +}; >>> + >>> /* ------ END-EXPECTED-OUTPUT ------ */ >>> >>> int f(struct root_struct *s) >>> -- >>> 2.34.1 >>>
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