ocaml/libs: Fill build failure due to unused variable in ocaml macro

On Fedora 40, the build fails with:

    In file included from domain_getinfo_stubs_v1.c:10:
    domain_getinfo_stubs_v1.c: In function 'xsd_glue_failwith':
    /usr/lib64/ocaml/caml/memory.h:275:29: error: unused variable 'caml__frame' [-Werror=unused-variable]
      275 |   struct caml__roots_block *caml__frame = *caml_local_roots_ptr
          |                             ^~~~~~~~~~~
    domain_getinfo_stubs_v1.c:48:9: note: in expansion of macro 'CAMLparam0'
      48 |         CAMLparam0();
         |         ^~~~~~~~~~
    cc1: all warnings being treated as errors

The CAMLparam0 macro is defined in /usr/lib64/ocaml/caml/memory.h:255 as:

    #define CAMLparam0()                                                    \
      struct caml__roots_block** caml_local_roots_ptr =                     \
        (DO_CHECK_CAML_STATE ? Caml_check_caml_state() : (void)0,           \
         &CAML_LOCAL_ROOTS);                                                \
      struct caml__roots_block *caml__frame = *caml_local_roots_ptr

We can't modify the macro.  But, it turns out there's a CAMLnoreturn macro
with the sole purpose of masking this warning.

Fixes: a6576011a4d2 ("ocaml/libs: Implement a dynamically-loaded plugin for Xenctrl.domain_getinfo")
Signed-off-by: Javi Merino <javi.merino@cloud.com>
Acked-by: Christian Lindig <christian.lindig@cloud.com>

diff --git a/tools/ocaml/libs/xsd_glue/domain_getinfo_plugin_v1/domain_getinfo_stubs_v1.c b/tools/ocaml/libs/xsd_glue/domain_getinfo_plugin_v1/domain_getinfo_stubs_v1.c
index 7be386f4d4c2b089a6adca4cb6d1a091c6d6747c..963cec8883277c5b036b485111339c7472d7a705 100644 (file)
--- a/tools/ocaml/libs/xsd_glue/domain_getinfo_plugin_v1/domain_getinfo_stubs_v1.c
+++ b/tools/ocaml/libs/xsd_glue/domain_getinfo_plugin_v1/domain_getinfo_stubs_v1.c
@@ -69,6 +69,7 @@ static void Noreturn xsd_glue_failwith(
        free(str);
 
        caml_raise_with_arg(*caml_named_value("xsg.error_v1"), msg);
+       CAMLnoreturn;
 }
 #define xsd_glue_failwith(xch) xsd_glue_failwith(xch, __func__, __LINE__)