Скачать или смотреть How to Execute a Generic Target in a C Makefile

Discover how to properly use a `generic target` in a C Makefile to compile your source files seamlessly!
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This video is based on the question https://stackoverflow.com/q/64554210/ asked by the user 'Lunar Cultist' ( https://stackoverflow.com/u/11121258/ ) and on the answer https://stackoverflow.com/a/64562853/ provided by the user 'the busybee' ( https://stackoverflow.com/u/11294831/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Execute a Generic Target in a C Makefile

If you're delving into C programming and using Makefiles, you might have stumbled upon an issue when trying to compile multiple source files into object files. You've set up a Makefile but find that generating object files from the .c files isn’t working as expected. This post will guide you through understanding the issue and how to resolve it effectively.

The Problem: Makefile Syntax Issues

You want to create a Makefile that compiles each .c file in your directory into an object .o file with the same name. But the original syntax in your Makefile likely expands to existing files only, which leads to problems when trying to compile. Your initial Makefile snippet is as follows:

[[See Video to Reveal this Text or Code Snippet]]

Why It Doesn’t Work

The line all: *.o expands to the object files that already exist in your directory. If no object files are present, this rule does nothing, which is likely the root cause of your issue. Essentially, it's not defining a target that will generate the .o files from .c files correctly.

The Solution: Proper Syntax for Generating Object Files

To solve this problem, you need a more dynamic approach that collects all the .c files in your directory and specifies the corresponding .o files as targets. Here’s how you can do it:

Step-by-Step Breakdown

Use of wildcard Function: This function allows Make to collect all .c files in your directory.

Exchange the Extension: Use patsubst to replace the .c extension with .o.

Update the Target: Modify your all target to link to these object files.

The modified Makefile with proper functions will look like this:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Changes

$(wildcard *.c): This function retrieves all the .c files in your current directory.

$(patsubst %.c, %.o, ...): This changes the file extension from .c to .o, effectively mapping each source file to its corresponding object file.

Important Note

It's worth considering why you might want to explicitly list object files in your Makefile. Doing so can help with clarity and ensure that your Makefile remains understandable, especially in larger projects. However, using wildcards becomes increasingly handy when dealing with many source files.

Conclusion

By employing the wildcard and patsubst functions in your Makefile, you ensure that you're dynamically identifying all necessary source files and compiling them correctly into object files. This approach provides flexibility and makes your build process more efficient.

Happy coding! If you have any questions or need further assistance, feel free to ask in the comments below!