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eatonphil
> For the C “FFI” he used standard dynamic linking, not dlopen(). This distinction is important, since it really makes a difference in the benchmark. There’s a potential argument about whether or not this is a fair comparison to an actual FFI, but, regardless, it’s still interesting to measure
jcelerier
With clang, just compiling with -fno-plt gives me:

    jit: 1.003483 ns/call
    plt: 1.254158 ns/call
    ind: 1.254616 ns/call
GCC does not seem to support it though, even if it accepts the flag and gives me:

    jit: 1.003483 ns/call
    plt: 1.502089 ns/call
    ind: 1.254616 ns/call
(tried everything I could think of that would have a chance to make the PLT disappear:

    cc -fno-plt -Bsymbolic -fno-semantic-interposition -flto -std=c99 -Wall -Wextra -O3 -g3 -Wl,-z,relro,-z,now -o benchmark benchmark.c ./empty.so -ldl
without any change on GCC)
arinlen
> There’s a potential argument about whether or not this is a fair comparison to an actual FFI, but, regardless, it’s still interesting to measure (...)

If there's interest in measuring dynamic linking then wouldn't there be an interest in measuring it on all languages that support dynamic linking?

qalmakka
I'm always pretty surprised when I find out most people writing C or C++ have no idea that PLTs exist. They have a small but not negligible cost.
miohtama
Is there anything akin FFI but with static linking for any foreign (non C) language?
tlb
Calling WebAssembly from Javascript, sort of?

In the early Python 2 era there was an option to build an interpreter binary with statically linked C stubs, and it was noticeably faster and let you access Python data structures from C. I used it for robotics code for speed. It was inconvenient because you had to link in all the modules you needed.

fweimer
For OpenJDK, there is JEP 178: https://openjdk.java.net/jeps/178 I haven't seen it used in practice.

Ocaml's C-implemented functions are linked statically. But like JNI, the C functions have special names and type signatures, so it is slightly different from, say, ctypes in Python.

CGO for Go is statically linked, too. Its overhead stems from significant differences between the Go and C world. The example uses dynamic linking, but it would not have to do that.

junon
The question as it stands makes a few assumptions I don't think one can make, and as such is a bit tricky to answer cleanly, but I'll try.

Yes it's just called linking. The language needs to be aware of calling conventions and perhaps side effects and be prepared for no additional intrinsic support for higher level features.

It probably also needs to be able to read C headers, because C symbols do not contain type signatures like many C++ compilers add.

There's no "library" or some out of the box solution for this, if that's what you're asking. This boils down to how programs are constructed and, moreso, how CPUs work.

In most (all?) cases, anything higher level than straight-up linking is headed toward FFI territory.

samatman
LuaJIT can use the FFI against statically linked object code just fine, I'm not sure if that answers your question since in this context it must be embedded in a C program.

It's a hard requirement of static linking that you have just one binary so it might, answer your question that is.

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