2025-07-12 12:43:17 -04:00
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Codon can be called from C/C++ code by compiling to a
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shared library that can be linked to a C/C++ application.
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Codon functions can be made externally visible by annotating
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them with `@export` decorator:
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2022-07-26 16:08:42 -04:00
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``` python
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@export
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def foo(n: int):
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for i in range(n):
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print(i * i)
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return n * n
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```
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Note that only top-level, non-generic functions can be exported. Now we
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can create a shared library containing `foo` (assuming source file
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2025-07-12 12:43:17 -04:00
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`foo.codon`):
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2022-07-26 16:08:42 -04:00
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``` bash
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2023-05-23 17:59:26 -04:00
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codon build --relocation-model=pic --lib -o libfoo.so foo.codon
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2022-07-26 16:08:42 -04:00
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```
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2023-05-23 17:59:26 -04:00
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Now we can call `foo` from a C program (if you're using C++, mark the
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Codon function as `extern "C"`):
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2022-07-26 16:08:42 -04:00
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``` c
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#include <stdint.h>
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#include <stdio.h>
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int64_t foo(int64_t);
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2023-05-23 17:59:26 -04:00
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// In C++, it would be:
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// extern "C" int64_t foo(int64_t);
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2022-07-26 16:08:42 -04:00
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int main() {
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printf("%llu\n", foo(10));
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}
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```
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Compile:
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``` bash
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gcc -o foo -L. -lfoo foo.c # or g++ if using C++
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2022-07-26 16:08:42 -04:00
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```
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2025-07-12 12:43:17 -04:00
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Now running `./foo` will invoke `foo()` as defined in Codon, with an
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2022-07-26 16:08:42 -04:00
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argument of `10`.
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2023-05-23 17:59:26 -04:00
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Note that if the generated shared library is in a non-standard path, you
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can either:
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- Add the `rpath` to the `gcc` command: `-Wl,-rpath=/path/to/lib/dir`
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- Add the library path to `LD_LIBRARY_PATH` (or `DYLD_LIBRARY_PATH` if
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using macOS): `export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/path/to/lib/dir`.
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2025-07-13 11:27:01 -04:00
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Type conversions between Codon and C/C++ are detailed [here](cpp-from-codon.md#type-conversions).
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