comphead commented on code in PR #18672:
URL: https://github.com/apache/datafusion/pull/18672#discussion_r2554635824
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datafusion/ffi/src/lib.rs:
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@@ -58,5 +58,33 @@ pub extern "C" fn version() -> u64 {
version.major
}
+static LIBRARY_MARKER: u8 = 0;
+
+/// This utility is used to determine if two FFI structs are within
+/// the same library. It is possible that the interplay between
+/// foreign and local functions calls create one FFI struct that
+/// references another. It is helpful to determine if a foreign
+/// struct is truly foreign or in the same library. If we are in the
+/// same library, then we can access the underlying types directly.
+///
+/// This function works by checking the address of the library
+/// marker. Each library that implements the FFI code will have
+/// a different address for the marker. By checking the marker
+/// address we can determine if a struct is truly Foreign or is
Review Comment:
so foreign means the function pointer comes from another library? can it be
the same library but different version? like jvm hell?
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