main.ll

declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)

declare void @styx_alloc(i8**, i64)
declare void @styx_list_objects()

define i32 @main() gc "shadow-stack" {
entry:
    %int_size_ptr = getelementptr { i8*, i32 }* null, i32 1
    %int_size = ptrtoint { i8*, i32 }* %int_size_ptr to i64

    %x = alloca { i8*, i32 }*
    %xptr = bitcast { i8*, i32 }** %x to i8**
    call void @llvm.gcroot(i8** %xptr, i8* null)
    call void @styx_alloc(i8** %xptr, i64 %int_size)

    %y = alloca { i8*, i32 }*
    %yptr = bitcast { i8*, i32 }** %y to i8**
    call void @llvm.gcroot(i8** %yptr, i8* null)
    call void @styx_alloc(i8** %yptr, i64 %int_size)

    call void @styx_list_objects()
    ret i32 0
}

runtime.cpp

#include <cstdint>
#include <iostream>

extern "C" void styx_alloc(void** target, std::uint64_t size) {
    *target = operator new(size);
}

struct FrameMap {
    std::int32_t numRoots;
    std::int32_t numMeta;
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wzero-length-array"
    const void* meta[0];
#pragma clang diagnostic pop
};

struct StackEntry {
    StackEntry* next;
    const FrameMap* map;
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wzero-length-array"
    void* roots[0];
#pragma clang diagnostic pop
};

extern "C" StackEntry* llvm_gc_root_chain;

extern "C" void styx_list_objects() {
    for (auto entry = llvm_gc_root_chain; entry != nullptr;
         entry = entry->next) {
        for (auto i = 0; i < entry->map->numRoots; ++i) {
            std::cout << entry->roots[i] << '\n';
        }
    }
}