Build system

Introduction

mdepx's build system is a set of python3 scripts located in mdepx/tools/ directory.

It compiles your application and OS, links all together to the ELF executable.

Files to build, compile flags and macroses to define are described in a config file.

Config file syntax is heavily inspired by libucl and nginx configuration file and has JSON-like structure, hence it is fully convertable to JSON.

Main principles of configuration file

• Everything in the config is 'key value' terminated with a colon ';'.
• Value is a list of strings or a dict (a context leaf).
• Same key could be presented many times, and all its values are appended to a list by order of parsing.
• A context leaf inherits properties (options / compile flags) from its parent.

Example

A config file:

key value;

value {
    key val1 val2;
    key val3;

    # comment
    param 3;

    val1 {
        k v;
    };

    val2 {
        key value;
        value {
                a b;
        };
    };
};

will be presented in JSON as:

{
    'key': ['value'],
    'value': {
        'key': ['val1', 'val2', 'val3'],
        'param': ['3'],
        'val1': {
            'k': ['v']
        },
        'val2': {
            'key': ['value'],
            'value': {
                'a': ['b']
            }
        }
    }
}

Invoking a build

In your application directory create a Makefile:

all:
    @python3 -B mdepx/tools/emitter.py -d mdepx.conf

Environment variables

While these settings could be described in the config file using corresponding directives, it is possible to pass them as environment variables (for instance from a Makefile):

• CROSS_COMPILE

Sets a path to a toolchain triple that will be used for compiling and linking.

• CC
• LD

Sets a compiler and a linker path individually.

• CFLAGS
• AFLAGS

C and Assembler flags to pass to the compiler.

Configuration file directives

---

Syntax: module modname;

A pre-processor directive that:

• opens module.conf file from the modname directory. If file exists then it puts file's body to the current context leaf;
• includes a modname context to processing.

---

Syntax: options optname;

Expands entries from the optname leaf to the current context and includes them to processing.

Example:

module1 {
    objects obj1.o obj2.o;
    options aaa;

    aaa {
        objects obj3.o;
        key value;
    };
};

will be transformed to:

module1 {
    objects obj1.o obj2.o obj3.o;
    key value;
};

---

Syntax: append-search-path path [path1 ..];

Adds -Ipath [-Ipath1] to the compiler.

---

Syntax: set-search-path path [path1 ..];

Replaces search-path inherited from parent context with -Ipath [-Ipath1].

---

Syntax: objects obj.o [obj1.o ..];

Includes objects to the build (compilation and linking stages). Object names must end with '.o' or '.a'. The corresponsing '.c' or '.S' file for the object '.o' will be passed to a compiler. Archives '.a' will be added to the tail of the objects list to link.

---

Syntax: link ldscript filename;

Invokes linker with provided ldscript as relative path to a linker script. All the compiled objects will be passed to a linker. filename is an output ELF file.

---

Syntax: prefix string;

Sets initial prefix for macroses that will be passed to a compiler.

Example:

module1 {
    prefix mdx;
    module aaa;
    options bbb;

    aaa {
        flag 1;
    };

    bbb {
        flag 2;
    };
};

Macroses will be collected and passed to a compiler as:

cc -DMDX_AAA -DMDX_AAA_FLAG=1 -DMDX_BBB -DMDX_FLAG=2 ..

Note that macroses are global and will be passed to compiler regardless of object.