Build system

Managing big source files

We’ve compiled a small editor so far. But Some bad signs are beginning to appear.

• We’ve had only one C source file and put everything in it. We need to sort it out.
• There are two compilers, gcc and glib-compile-resources. We should control them by one building tool.

These ideas are useful to manage big source files.

Divide a C source file into two parts.

When you divide C source file into several parts, each file should contain one thing. For example, our source has two things, the definition of TfeTextView and functions related to GtkApplication and GtkApplicationWindow. It is a good idea to separate them into two files, tfetextview.c and tfe.c.

• tfetextview.c includes the definition and functions of TfeTextView.
• tfe.c includes functions like main, app_activate, app_open and so on, which relate to GtkApplication and GtkApplicationWindow

Now we have three source files, tfetextview.c, tfe.c and tfe3.ui. The 3 of tfe3.ui is like a version number. Managing version with filenames is one possible idea but it may make bothersome problem. You need to rewrite filename in each version and it affects to contents of source files that refer to filenames. So, we should take 3 away from the filename.

In tfe.c the function tfe_text_view_new is invoked to create a TfeTextView instance. But it is defined in tfetextview.c, not tfe.c. The lack of the declaration (not definition) of tfe_text_view_new makes error when tfe.c is compiled. The declaration is necessary in tfe.c. Those public information is usually written in header files. It has .h suffix like tfetextview.h And header files are included by C source files. For example, tfetextview.h is included by tfe.c.

All the source files are listed below.

tfetextview.h

@@@include tfe4/tfetextview.h @@@

tfetextview.c

@@@include tfe4/tfetextview.c @@@

tfe.c

@@@include tfe4/tfe.c @@@

The ui file tfe.ui is the same as tfe3.ui in the previous section.

tfe.gresource.xml

@@@include tfe4/tfe.gresource.xml @@@

Dividing a file makes it easy to maintain source files. But now we face a new problem. The building step increases.

• Compiling the ui file tfe.ui into resources.c.
• Compiling tfe.c into tfe.o (object file).
• Compiling tfetextview.c into tfetextview.o.
• Compiling resources.c into resources.o.
• Linking all the object files into application tfe.

Build tools manage the steps. I’ll show you three build tools, Meson and Ninja, Make and Rake. Meson and Ninja is recommended as a C build tool, but others are also fine. It’s your choice.

Meson and Ninja

Meson and Ninja is one of the most popular building tool to build C language program. Many developers use Meson and Ninja lately. For example, GTK 4 uses them.

You need to make meson.build file first.

@@@include tfe4/meson.build @@@

• 1: The function project defines things about the project. The first parameter is the name of the project and the second is the programming language.
• 2: dependency function defines a dependency that is taken by pkg-config. We put gtk4 as an argument.
• 5: import function imports a module. In line 5, the gnome module is imported and assigned to the variable gnome. The gnome module provides helper tools to build GTK programs.
• 6: .compile_resources is a method of the gnome module and compiles files to resources under the instruction of xml file. In line 6, the resource filename is resources, which means resources.c and resources.h, and xml file is tfe.gresource.xml. This method generates C source file by default.
• 8: Defines source files.
• 10: Executable function generates a target file by compiling source files. The first parameter is the filename of the target. The following parameters are source files. The last parameter is an option dependencies. gtkdep is used in the compilation.

Now run meson and ninja.

$ meson _build
$ ninja -C _build

Then, the executable file tfe is generated under the directory _build.

$ _build/tfe tfe.c tfetextview.c

A window appears. It includes a notebook with two pages. One is tfe.c and the other is tfetextview.c.

For further information, see The Meson Build system.

Make

Make is a build tool created in 1976. It was a standard build tool for C compiling, but lately it is replaced by Meson and Ninja.

Make analyzes Makefile and executes compilers. All instructions are written in Makefile.

For example,

sample.o: sample.c
    gcc -o sample.o sample.c

Malefile above consists of three elements, sample.o, sample.c and gcc -o sample.o sample.c.

• sample.o is a target.
• sample.c is a prerequisite.
• gcc -o sample.o sample.c is a recipe. Recipes follow tab characters, not spaces. (It is very important. Use tab, or make won’t work as you expected).

The rule is:

If a prerequisite modified later than a target, then make executes the recipe.

In the example above, if sample.c is modified after the generation of sample.o, then make executes gcc and compile sample.c into sample.o. If the modification time of sample.c is older then the generation of sample.o, then no compiling is necessary, so make does nothing.

The Makefile for tfe is as follows.

@@@include tfe4/Makefile @@@

You just type make and everything will be done.

$ make
gcc -c -o tfe.o `pkg-config --cflags gtk4` tfe.c
gcc -c -o tfetextview.o `pkg-config --cflags gtk4` tfetextview.c
glib-compile-resources tfe.gresource.xml --target=resources.c --generate-source
gcc -c -o resources.o `pkg-config --cflags gtk4` resources.c
gcc -o tfe tfe.o tfetextview.o resources.o `pkg-config --libs gtk4`

I used only very basic rules to write this Makefile. There are many more convenient methods to make it more compact. But it will be long to explain it. So I want to finish with make and move on to the next topic.

You can download “Gnu Make Manual” from GNU website.

Rake

Rake is a similar program to make. It is written in Ruby language. If you don’t use Ruby, you don’t need to read this subsection. However, Ruby is really sophisticated and recommendable script language.

• Rakefile controls the behavior of rake.
• You can write any Ruby code in Rakefile.

Rake has task and file task, which is similar to target, prerequisite and recipe in make.

@@@include tfe4/Rakefile @@@

The contents of the Rakefile is almost same as the Makefile in the previous subsection.

• 3-8: Defines target file, source files and so on.
• 1, 10 Requires rake/clean library. And clean files are added to CLEAN. The files included by CLEAN will be removed when rake clean is typed on the command line.
• 12: The default target depends on targetfile. The task default is the final goal of tasks.
• 14-16: targetfile depends on objfiles. The variable t is a task object.
  • t.name is a target name
  • t.prerequisites is an array of prerequisites.
  • t.source is the first element of prerequisites.
• sh is a method to give the following string to shell as an argument and executes the shell.
• 18-23: An each iterator of the array objfiles. Each object depends on corresponding source file.
• 25-27: Resource file depends on ui file.

Rakefile might seem to be difficult for beginners. But, you can use any Ruby syntax in the Rakefile, so it is really flexible. If you practice Ruby and Rakefile, it will be highly productive tools.

For further information, see Rake tutorial for beginners.