ctest: Improper codegen for `typedef struct { ... } foo`

[cbarrick]

When a typedef is defined for an anonymous struct like this:

typedef struct {
  uint8_t *base;
  size_t len;
} nghttp2_vec;

ctest will generate a test like this:

CTEST_EXTERN uint64_t ctest_size_of__nghttp2_vec(void) { return sizeof(struct nghttp2_vec); }

Unfortunately, in the original typedef, the struct was never named. This makes struct nghttp2_vec invalid. This leads to build errors like:

warning: systest@0.1.0: /Users/runner/work/libnghttp2-sys/libnghttp2-sys/target/debug/build/systest-11de373a3de40a3c/out/ctest.c:807:65: error: invalid application of 'sizeof' to an incomplete type 'struct nghttp2_vec'
warning: systest@0.1.0:   807 | CTEST_EXTERN uint64_t ctest_size_of__nghttp2_vec(void) { return sizeof(struct nghttp2_vec); }
warning: systest@0.1.0:       |                                                                 ^     ~~~~~~~~~~~~~~~~~~~~
warning: systest@0.1.0: /Users/runner/work/libnghttp2-sys/libnghttp2-sys/target/debug/build/systest-11de373a3de40a3c/out/ctest.c:807:79: note: forward declaration of 'struct nghttp2_vec'
warning: systest@0.1.0:   807 | CTEST_EXTERN uint64_t ctest_size_of__nghttp2_vec(void) { return sizeof(struct nghttp2_vec); }
warning: systest@0.1.0:       |                                                                               ^

Instead, the test should probably use nghttp2_vec instead of struct nghttp2_vec.

[cbarrick]

I think this applies to unions as well as structs.

[tgross35]

This information isn't present in Rust source so there isn't anything ctest could do better here. Instead, you should use rename_struct_ty to re-emit the struct name without a prefix, like we do here

libc/libc-test/build.rs

Lines 513 to 520 in 0a15ee8

	cfg.rename_struct_ty(move |ty| {
	match ty {
	// Just pass all these through, no need for a "struct" prefix
	"FILE" | "DIR" | "Dl_info" | "Elf32_Phdr" | "Elf64_Phdr" => Some(ty.to_string()),
	_ => None,
	}
	});

.

[cbarrick]

This information isn't present in Rust source so there isn't anything ctest could do better here.

I see. ctest doesn't read the C source. I guess this makes sense intuitively, since ctest won't know which flags were passed to bindgen, but that wasn't obvious to me at first.

you should use rename_struct_ty to re-emit the struct name without a prefix

This is definitely non-obvious. It was not clear from the docs that this removes the struct keyword from the type.

Thanks for the help. It seems rename_struct_ty will solve my immediate problem.

[tgross35]

Docs for ctest could certainly be improved, PRs are welcome if you are interested!

[cbarrick]

PR #5000 for the docs update