v/examples/call_v_from_c/README.md

## A simple example to show how to call a function written in v from c

### Compile as a shared library

#### On Linux:

Step 1: Compile the v code to a shared library using `v -cc gcc -shared v_test_print.v` or
`v -cc gcc -shared v_test_math.v`.

Step 2: Compile the c file using `gcc test_print.c v_test_print.so -o test_print -Wl,-rpath=.` or
`gcc test_math.c v_test_math.so -o test_math -Wl,-rpath=.`.

Step 3: Run the compiled c file using `./test_print` or `./test_math`.


#### On Mac OSX:

On Mac OSX, libgc can be obtained from homebrew by `brew install libgc`.
During compiling and/or linking, `-I/usr/local/include -L/usr/local/lib` (for x86_64),
or `-I/opt/homebrew/include -L/opt/homebrew/lib` (for arm64) can be added depending the arch.

Step 1: Compile the v code to a shared library using `v -cc gcc -shared v_test_print.v` or
`v -cc gcc -shared v_test_math.v`.

Step 2: Compile the c file using `gcc test_print.c v_test_print.dylib -o test_print` or
`gcc test_math.c v_test_math.dylib -o test_math`.

Step 3: Run the compiled c file using `LD_LIBRARY_PATH=. ./test_print` or
`LD_LIBRARY_PATH=. ./test_math`.

#### On Windows:

Step 1: Compile the v code to a shared library using `v -cc gcc -shared v_test_print.v` or
`v -cc gcc -shared v_test_math.v`.

Step 2: Compile the c file using `gcc test_print.c v_test_print.dll -o test_print.exe` or
`gcc test_math.c v_test_math.dll -o test_math.exe`.

Step 3: Run the compiled c file using `test_print.exe` or `test_math.exe`.

### Compile as a c file

***Requirements: `libgc` must be installed***

Step 1: Compile the v code to a shared library using
`v -shared -cc gcc -o v_test_print.c v_test_print.v` or
`v -shared -cc gcc -o v_test_math.c v_test_math.v`.

*Specifying the output with a `.c` extension will generate the corresponding C source file.*

Step 2: Compile the c file using `gcc test_print.c v_test_print.c -o test_print -lgc` or
`gcc test_math.c v_test_math.c -o test_math -lgc -lm`.

Step 3: Run the compiled c file using `./test_print` or `./test_math`.