dns2utf8 / hour_glass

C++ Frontend - Rust Backend

hour_glass

This is a PoC (Proof of Concept) using Rust as a Backend for C++.

This is based upon the work of Alex's Rust FFI Examples.

How it works

• The rust library is included as a static library.
• The C++ facade lives inside the rust:: namespace.
• A C++ std::unique_ptr manages the pointer to the Rust IntSorter ensuring it will never pass a nullpointer to the Rust functions. This prevents undefined behavior.

Contributions

If you would like to add/fix or change something, send a PR or open an issue.

Running your self

Run:

make clean all optimized

For a debug build run:

make clean all

Requirements

• make
• clang or clang++ or gcc or g++ with at least c89 and c++11. You may mix the compilers, please run make clean when switching.
• cargo and rustc >= 1.11.0

Expected output:

$ make
mkdir -p target
clang -g -std=c89 -Wall -Werror -pedantic -o target/main_c.o -c src/main.c
cargo build 
   Compiling hour_glass v0.1.0 (file:///home/vp/tmp/hour_glass)
note: link against the following native artifacts when linking against this static library
note: the order and any duplication can be significant on some platforms, and so may need to be preserved
note: library: dl
note: library: pthread
note: library: gcc_s
note: library: c
note: library: m
note: library: rt
note: library: util
clang -g -std=c89 -Wall -Werror -pedantic -o target/hgc target/main_c.o target/debug/libintsorter.a -Wl,--gc-sections -lpthread
clang++ -g -std=c++11 -Wall -Werror -pedantic -o target/main_cpp.o -c src/main.cpp
clang++ -g -std=c++11 -Wall -Werror -pedantic -o target/hgcpp target/main_cpp.o target/debug/libintsorter.a -Wl,--gc-sections -lpthread
######## Testing from C
target/hgc
Hi C
0: 42
1: 23
2: 13
3: 12
4: 6
5: 0
6: 0
Destroy IntSorter Instance
Bye C
######## Testing from C++
target/hgcpp
Hi C++
0: 42
1: 23
2: 13
3: 12
4: 6
5: 0
6: 0
Bye C++
Destroy IntSorter Instance

Note the reverse order of rusts "Destroy IntSorter Instance" message. The reason is in C we explicitily destroy the IntSorter and in C++ the end of the scope destroys the object.

hour_glass's Issues

Rust FFI constructor/destructor should use raw pointers

Rather than returning and accepting Box<IntSorter>, we should make use of Box::into_raw and Box::from_raw to only pass around FFI-safe types instead.