Bundled version of libmimalloc-sys will have problems with modern C compilers, but mimalloc_rust is a bit weird upstream

[NHOrus]

purpleprotocol/mimalloc_rust#109 - this may be irrelevant, but it also may be suspicious in light of xz backdooring.

https://bugs.gentoo.org/944110 - for problems with GCC-15 and Clang-19, to be precisely building libmimalloc-sys fails to compile with error

warning: [email protected]: In file included from c_src/mimalloc/src/static.c:25:
warning: [email protected]: c_src/mimalloc/src/os.c: In function 'mi_os_resetx':
warning: [email protected]: c_src/mimalloc/src/os.c:993:35: error: implicit declaration of function 'ATOMIC_VAR_INIT'; did you mean 'ATOMIC_FLAG_INIT'? [-Wimplicit-function-declaration]
warning: [email protected]:   993 |   static _Atomic(size_t) advice = ATOMIC_VAR_INIT(MADV_FREE);
warning: [email protected]:       |                                   ^~~~~~~~~~~~~~~
warning: [email protected]:       |                                   ATOMIC_FLAG_INIT
warning: [email protected]: c_src/mimalloc/src/os.c:993:35: error: initializer element is not constant
warning: [email protected]: In file included from c_src/mimalloc/src/static.c:38:
warning: [email protected]: c_src/mimalloc/src/init.c: At top level:
warning: [email protected]: c_src/mimalloc/src/init.c:28:3: error: initializer element is not constant
warning: [email protected]:    28 |   ATOMIC_VAR_INIT(0), // xthread_free
warning: [email protected]:       |   ^~~~~~~~~~~~~~~
warning: [email protected]: c_src/mimalloc/src/init.c:28:3: note: (near initialization for '_mi_page_empty.xthread_free')
warning: [email protected]: c_src/mimalloc/src/init.c:29:3: error: initializer element is not constant
warning: [email protected]:    29 |   ATOMIC_VAR_INIT(0), // xheap
warning: [email protected]:       |   ^~~~~~~~~~~~~~~
warning: [email protected]: c_src/mimalloc/src/init.c:29:3: note: (near initialization for '_mi_page_empty.xheap')
warning: [email protected]: c_src/mimalloc/src/init.c:94:3: error: initialization of 'mi_block_t *' {aka 'struct mi_block_s *'} from 'int' makes pointer from integer without a cast [-Wint-conversion]
warning: [email protected]:    94 |   ATOMIC_VAR_INIT(NULL),
warning: [email protected]:       |   ^~~~~~~~~~~~~~~
warning: [email protected]: c_src/mimalloc/src/init.c:94:3: note: (near initialization for '_mi_heap_empty.thread_delayed_free')
warning: [email protected]: c_src/mimalloc/src/init.c:94:3: error: initializer element is not constant
warning: [email protected]: c_src/mimalloc/src/init.c:94:3: note: (near initialization for '_mi_heap_empty.thread_delayed_free')
warning: [email protected]: c_src/mimalloc/src/init.c:126:3: error: initialization of 'mi_block_t *' {aka 'struct mi_block_s *'} from 'int' makes pointer from integer without a cast [-Wint-conversion]
warning: [email protected]:   126 |   ATOMIC_VAR_INIT(NULL),
warning: [email protected]:       |   ^~~~~~~~~~~~~~~
warning: [email protected]: c_src/mimalloc/src/init.c:126:3: note: (near initialization for '_mi_heap_main.thread_delayed_free')
warning: [email protected]: c_src/mimalloc/src/init.c:126:3: error: initializer element is not constant
warning: [email protected]: c_src/mimalloc/src/init.c:126:3: note: (near initialization for '_mi_heap_main.thread_delayed_free')
warning: [email protected]: c_src/mimalloc/src/init.c:328:39: error: initializer element is not constant
warning: [email protected]:   328 | static _Atomic(size_t) thread_count = ATOMIC_VAR_INIT(1);
warning: [email protected]:       |                                       ^~~~~~~~~~~~~~~