How to use the command 'gnatmake' (with examples)

GNATmake is a robust, low-level build tool specifically designed for compiling Ada programs. As part of the GNAT toolchain, it automates the process of building complex projects by managing source files and dependencies efficiently. GNATmake ensures that only the necessary files are recompiled, thus optimizing build time. It also provides options to customize the final executable and control the compilation process.

Use case 1: Compile an executable

Code:

gnatmake source_file1.adb source_file2.adb ...

Motivation: When developing an Ada program, you may have multiple source files that need to be compiled together to form a single executable. This command allows for the compilation and linking of all necessary source files in a project, ensuring they are properly assembled into a final executable. This is especially useful for large projects where manually tracking dependencies and compiling each file individually would be time-consuming and error-prone.

Explanation:

• gnatmake: This is the command that invokes the GNATmake build tool.
• source_file1.adb, source_file2.adb, ...: These are the Ada source files that you want to compile. Each source file can contain various units like packages, procedures, or functions, and the GNATmake tool will manage their dependencies automatically.

Example Output:

gcc -c source_file1.adb
gcc -c source_file2.adb
gcc source_file1.o source_file2.o -o source_file1

This output indicates each source file being compiled into an object file (e.g., source_file1.o) and then linking them together into an executable named source_file1.

Use case 2: Set a custom executable name

Code:

gnatmake -o executable_name source_file.adb

Motivation: There may be situations where you want your resulting executable to have a specific name that is different from the default behavior (where the executable is named after the main Ada source file). This could be for clarity, organization, or meeting a naming convention in a larger project. The -o option allows you to set a custom name for the generated executable, enhancing both clarity and integration into larger build systems or scripts.

Explanation:

• -o: This option allows you to specify a custom name for the final executable.
• executable_name: This is the name you want for the final executable, replacing the default name derived from the main source file.
• source_file.adb: The Ada source file that serves as the entry point to your program, containing the main procedure.

Example Output:

gcc -c source_file.adb
gcc source_file.o -o executable_name

This output shows the source file being compiled into an object file and then linked into an executable with the custom name executable_name.

Use case 3: Force recompilation

Code:

gnatmake -f source_file.adb

Motivation: During development, you might make changes to your code that don’t automatically trigger recompilation due to GNATmake’s dependency checks. This can occur if changes are made to external files or build settings. To ensure that all files are up-to-date with your latest modifications, you can use the force recompilation option. This command is crucial for ensuring the integrity and correctness of your build, making sure that no stale code is included in the final executable.

Explanation:

• -f: This flag forces GNATmake to recompile all source files, regardless of whether they appear up-to-date. It overrides the default behavior that only recompiles files deemed necessary based on dependencies and timestamp checks.
• source_file.adb: The main Ada source file for your program, serving as the entry point for compilation.

Example Output:

gcc -c source_file.adb
gcc -c dependent_file1.adb
gcc -c dependent_file2.adb
gcc source_file.o dependent_file1.o dependent_file2.o -o source_file

Here, the output shows all relevant source files being recompiled and linked, despite potential previous compilations, due to the use of the -f option.

Conclusion:

The gnatmake command is an essential tool for those working with Ada programming, offering a streamlined process to compile, link, and manage projects of varying complexity. By understanding its various options, such as setting custom executable names or forcing recompilation, developers can exert significant control over their build processes to fit their unique development needs. These capabilities illustrate the power and flexibility of the GNATmake toolchain, making it an indispensable resource in the Ada programming landscape.