Show HN: Cpi – Immediately compile and execute c++ program like a scripting lang

This is great! Nice to see another project in the history of C/C++ interpreters including:

- cling: https://root.cern.ch/cling

- cint: http://www.hanno.jp/gotom/Cint.html

- Ch: https://www.softintegration.com/

If people know of other ones, I'd love to hear about them in the comments!

This is a task on Rosetta:

https://rosettacode.org/wiki/Native_shebang

Also:

https://rosettacode.org/wiki/Multiline_shebang

I contributed the C one here.

Rather than using shebang notation for running C source files, which as noted leads to code which isn't legal input to a normal C compiler, there is a standard trick to please both the shell and the C compiler:

    #if 0
    /bin/env cpi "$0"
    exit
    #endif

And you don't need this cpi program depending on your tolerance for hacks:

    #if 0
    out=/tmp/$RANDOM
    gcc "$0" -o $out
    $out
    rm $out
    exit
    #endif

I do something very similar to this, but just using cmake and basic bash scripts to launch the compilation and then run the executable all at once. And for the interpreter mode, a bash script can just automatically dump that into a main function, and then compile and run it all at once.

It's cool, but you can set something up like this just a few lines of bash code.

The page claims that CPI is an interpreter, but as this post says it is not. It just uses a regular compiler to build the input, then fiddled with the file descriptors to hook up the new executable's I/O to cpi's existing fds.

If nothing else, the interactive mode is going to be a life saver for me.