From: Ezekiel Newren <ezekielnewren@xxxxxxxxx>
Why Rust primitive types should be used in C:
* Consistency across languages: Sharing the same type names makes it
easier to translate and refactor code across boundaries, and search
history.
* Clarity and ergonomics: The types f32 and f64 are clearer than
float and double. The types u64 or isize are easier to write than
uint64_t, or ptrdiff_t.
* Explicit intent: Inclusion of compat/rust_types.h signals other
readers that the code is designed, or being cleaned up, for Rust
interop.
* Character types: Rust's char is defined as an unsigned 32-bit type.
In contrast, C's char is an 8-bit type that is neither signed nor
unsigned. The u8 type should be used instead of C's char when
referring to bytes in memory.
* Keep the FFI boundary precise: When Rust calls into C, the C
interface should use Rust types exclusively in both functions and
structs. If a broad refactor would cause too much churn, C stub
functions may be used as an interim step.
Reasons to avoid c_* types (e.g. c_char, c_long) in Rust:
* Rust remains precise: Bringing c_* into Rust reintroduces the very
ambiguity Rust was designed to eliminate. Using only Rust
primitives keeps our code portable and predictable.
* One clear contract: Rust should define the interface with precise
types. C adapts through compat/rust_types.h, ensuring the boundary
is consistent and easy to audit.
* Future-proof interop: Other runtimes (Python, Go, Java, Wasm, etc.)
map cleanly onto Rust's primitives, but not onto c_*. Sticking with
Rust types makes bindings straightforward and avoids locking Git's
ABI to C's historical quirks.
Signed-off-by: Ezekiel Newren <ezekielnewren@xxxxxxxxx>
---
compat/rust_types.h | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
create mode 100644 compat/rust_types.h
diff --git a/compat/rust_types.h b/compat/rust_types.h
new file mode 100644
index 0000000000..af93d0a116
--- /dev/null
+++ b/compat/rust_types.h
@@ -0,0 +1,28 @@
+#ifndef COMPAT_RUST_TYPES_H
+#define COMPAT_RUST_TYPES_H
+
+#include <compat/posix.h>
+
+/*
+ * A typedef for bool is not needed because C bool and Rust bool are
+ * the same if #include <stdbool.h> is used.
+ */
+
+typedef uint8_t u8;
+typedef uint16_t u16;
+typedef uint32_t u32;
+typedef uint64_t u64;
+
+typedef int8_t i8;
+typedef int16_t i16;
+typedef int32_t i32;
+typedef int64_t i64;
+
+typedef float f32;
+typedef double f64;
+
+typedef size_t usize;
+typedef ptrdiff_t isize;
+typedef uint32_t rust_char;
+
+#endif /* COMPAT_RUST_TYPES_H */
--
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