tomo/docs/libraries.md

Tomo Library/Module Design

There are two ways to "import" code that is defined elsewhere: local files from the same project and shared library objects from another project. The first type of import (local files) is necessary for splitting large projects into smaller components for ease of understanding and compilation speed. The second type of import (shared libraries) is to allow you to install third party libraries or frameworks that can be used across many projects.

Local Imports

To see how local imports work, let's look at a simple file:

// File: foo.tm
my_variable := "hello"

When this file is compiled to a static object file by tomo -c foo.tm, it produces the following C header file and C source file:

// File: foo.tm.h
#pragma once
#include <tomo/tomo.h>

extern Text_t foo$my_variable;

// File: foo.tm.c
#include <tomo/tomo.h>
#include "foo.tm.h"

Text_t foo$my_variable = "hello";

Notice that the symbols defined here (foo$my_variable) use a file-based prefix that includes a dollar sign. C compilers support an extension that allows dollar signs in identifiers, and this allows us to use guaranteed-unique prefixes so symbols from one file don't have naming collisions with symbols in another file.

The C file is compiled by invoking the C compiler with something like: cc <flags...> -c foo.tm.c -o foo.tm.o

Now, what happens if we want to use the compiled object file?

// File: baz.tm
foo := use ./foo.tm

func say_stuff():
    say("I got $(foo.my_variable) from foo")

func main():
    say_stuff()

If I want to run baz.tm with tomo baz.tm then this transpiles to:

// File: baz.tm.h
#pragma once
#include <tomo/tomo.h>
#include "./foo.tm.h"

void baz$say_stuff();
void baz$main();

// File: baz.tm.c
#include <tomo/tomo.h>
#include "baz.tm.h"

public void baz$say_stuff()
{
    say(Texts(Text("I got "), foo$my_variable, Text(" from foo")));
}

public void baz$main()
{
    baz$say_stuff();
}

Then baz.tm.o is compiled to a static object with cc <flags...> -c baz.tm.c -o baz.tm.o.

Next, we need to create an actual executable file that will invoke baz$main() (with any command line arguments). To do that, we create a small wrapper program:

// File: /tmp/program.c
#include <tomo/tomo.h>
#include "baz.tm.h"
 
int main(int argc, char *argv[])
{
    tomo_init();
    if (argc > 1)
        errx(1, "This program doesn't take any arguments.");
    baz$main();
    return 0;
}

This program is compiled with the already-built object files to produce an executable binary called foo like this: cc <flags...> /tmp/program.c foo.tm.o baz.tm.o -o baz

Finally, the resulting binary can be executed to actually run the program!

Shared Library Imports

In Tomo, a shared library is built out of a directory that contains multiple .tm files. Each .tm file in the directory (excluding those that start with an underscore) will be compiled and linked together to produce a single libwhatever.so file and whatever.h file that can be used by other Tomo projects. You can build a library by running tomo -L dirname/ or tomo -L in the current directory.

Installing

If you additionally add the -I flag, Tomo will copy the entire directory (excluding files and directories that begin with . such as .git) into ~/.local/share/tomo/installed/ and create a symbolic link for the library's .so file in ~/.local/share/tomo/lib/.

Using Shared Libraries

To use a shared library, write a statement like use foo with an unqualified name (i.e. not an absolute or relative path like /foo or ./foo). When a program uses a shared library, that shared library gets dynamically linked to the executable when compiling, and all of the necessary symbol information is read from the source files during compilation.