[libc] [llvm] [libc] add basic arena allocator (PR #121173)

[Tristan Ross via llvm-commits]

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@@ -115,6 +115,16 @@
     "LIBC_ADD_NULL_CHECKS": {
       "value": true,
       "doc": "Add nullptr checks in the library's implementations to some functions for which passing nullptr is undefined behavior."
+    },
+    "LIBC_CONF_ALLOC_TYPE": {
+      "value": "LIBC_ALLOC_TYPE_ARENA",
+      "doc": "The implementation used for allocations, acceptable values are LIBC_ALLOC_TYPE_EXTERN, LIBC_ALLOC_TYPE_SCUDO, LIBC_ALLOC_TYPE_ARENA."
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RossComputerGuy wrote:

I'm not familiar with existing allocators being implemented. I could hook them up to support the option and general interface.

https://github.com/llvm/llvm-project/pull/121173