incompatible-pointer-types in c_generated_functions.c

[olafhering]

GCC 14 complains about incompatible pointer types:

[   13s] + dune installed-libraries
[   13s] bigarray               (version: 4.14.2)
[   13s] bigarray-compat        (version: 1.1.0)
[   13s] bytes                  (version: 4.14.2)
[   13s] compiler-libs          (version: 4.14.2)
[   13s] compiler-libs.bytecomp (version: 4.14.2)
[   13s] compiler-libs.common   (version: 4.14.2)
[   13s] compiler-libs.optcomp  (version: 4.14.2)
[   13s] compiler-libs.toplevel (version: 4.14.2)
[   13s] ctypes                 (version: 0.23.0)
[   13s] ctypes-foreign         (version: 0.23.0)
[   13s] ctypes.stubs           (version: 0.23.0)
[   13s] ctypes.top             (version: 0.23.0)
[   13s] dynlink                (version: 4.14.2)
[   13s] integers               (version: 0.7.0)
[   13s] integers.top           (version: 0.7.0)
[   13s] ocamldoc               (version: [distributed with OCaml])
[   13s] raw_spacetime          (version: 4.14.2)
[   13s] seq                    (version: 4.14.2)
[   13s] stdlib                 (version: 4.14.2)
[   13s] stdlib-shims           (version: 0.3.0)
[   13s] str                    (version: 4.14.2)
[   13s] threads                (version: 4.14.2)
[   13s] threads.none           (version: 4.14.2)
[   13s] threads.posix          (version: 4.14.2)
[   13s] uchar                  (version: 4.14.2)
[   13s] unix                   (version: 4.14.2)

[   15s] File "_build/.dune/default/src/c/dune", line 12, characters 9-30:
[   15s] 12 |   (names c_generated_functions helpers)
[   15s]               ^^^^^^^^^^^^^^^^^^^^^
[   15s] Command [137] exited with code 1:
[   15s] $ (cd _build/default/src/c && /usr/bin/gcc-14 -O2 -fno-strict-aliasing -fwrapv -pthread -Werror=implicit-function-declaration -Werror=return-type -Wno-deprecated-declarations -fPIC -pipe -D_FILE_OFFSET_BITS=64 -O2 -fno-strict-aliasing -fwrapv -pthread -Werror=implicit-function-declaration -Werror=return-type -Wno-deprecated-declarations -fPIC -pipe -g -I /usr/lib64/ocaml -I /usr/lib64/ocaml/bigarray-compat -I /usr/lib64/ocaml/ctypes -I /usr/lib64/ocaml/integers -I /usr/lib64/ocaml/stdlib-shims -I /usr/lib64/ocaml/threads -I . -o c_generated_functions.o -c c_generated_functions.c)
[   15s] c_generated_functions.c: In function ‘luv_stub_156_luv_get_getnameinfo_trampoline’:
[   15s] c_generated_functions.c:1177:4: error: initialization of ‘void (*)(uv_getnameinfo_t *, int,  const char *, const char *)’ {aka ‘void (*)(struct uv_getnameinfo_s *, int,  const char *, const char *)’} from incompatible pointer type ‘luv_getnameinfo_cb’ {aka ‘void (*)(struct uv_getnameinfo_s *, int,  char *, char *)’} [-Wincompatible-pointer-types]
[   15s]  1177 |    luv_get_getnameinfo_trampoline();
[   15s]       |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[   15s] c_generated_functions.c: In function ‘luv_stub_157_luv_getnameinfo’:
[   15s] c_generated_functions.c:1189:43: error: passing argument 3 of ‘luv_getnameinfo’ from incompatible pointer type [-Wincompatible-pointer-types]
[   15s]  1189 |    int x954 = luv_getnameinfo(x947, x948, x949, x950, x951);
[   15s]       |                                           ^~~~
[   15s]       |                                           |
[   15s]       |                                           void (*)(uv_getnameinfo_t *, int,  const char *, const char *) {aka void (*)(struct uv_getnameinfo_s *, int,  const char *, const char *)}
[   15s] In file included from c_generated_functions.c:8:
[   15s] helpers.h:177:64: note: expected ‘luv_getnameinfo_cb’ {aka ‘void (*)(struct uv_getnameinfo_s *, int,  char *, char *)’} but argument is of type ‘void (*)(uv_getnameinfo_t *, int,  const char *, const char *)’ {aka ‘void (*)(struct uv_getnameinfo_s *, int,  const char *, const char *)’}
[   15s]   177 |     uv_loop_t *loop, uv_getnameinfo_t *req, luv_getnameinfo_cb getnameinfo_cb,
[   15s]       |                                             ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~

[aantron]

Thanks!

For GCC 14, it looks like Luv will have to upgrade to ctypes 0.23.0 to use its ability to generate const-correct code, or work around this otherwise, perhaps with some more casts. See:

• Support for cv-qualifiers ("const" etc.) yallop/ocaml-ctypes#134
• Add support for 'const' and 'volatile' yallop/ocaml-ctypes#780
• Make string a view of ptr (const char), not ptr char yallop/ocaml-ctypes#782

[aantron]

Even more tricky, this is likely caused by ctypes 0.23.0 now translating string as const char*, which is the more correct behavior, but it makes the wrappers we currently have for handling ctypes' previous behavior of translating string as char* not only redundant, but harmful, causing these new warnings when we try to bind to the previous wrappers, whose whole purpose was to cast char* to const char*. I will delete them and require ctypes 0.23.0.

[aantron]

Would you be able to try this with the Luv commit ad7f953, from branch getnameinfo-constness, which is linked above? It makes the build warning-clean again on my machine, with ctypes 0.23.0.

[olafhering]

ad7f953 does indeed work. Thank you.

[aantron]

Thanks! Let me know if you'd like a release to opam.

[olafhering]

Well, if you don't mind: release early, release often.

With a new release I would be able to point the Haxe people to this issue, so that they can start porting their code to 0.5.13, or newer.

[aantron]

ocaml/opam-repository#26501