In embedded systems, every byte saved matters. While it’s standard practice to include whole headers like `stdio.h`, doing so can sometimes be unproductive in resource-limited environments.
Reasons:
1. Efficiency Over Everything: Including a header means bringing in a plethora of declarations, possibly even those we never use. This can bloat our code, leading to unnecessary memory usage.
2. The printf() Dilemma: Take `stdio.h` as an example. It houses the declaration for `printf()` but also for many other functions you might not touch. Why import a library for just one function?
3. The Benefits of Being Selective:
Lean Code: By declaring only what’s needed, we cut down overheads linked with processing unused parts of a header.
Steer Clear of Unwanted Dependencies: Full headers can sometimes conflict with our code or other libraries.
Tailored Implementation: Using a custom `printf()` for embedded applications? Ensure your declaration matches your specific version.
Swift Compilation: Minimizing compiler workload can speed up build times, a blessing in larger projects.
On the other side:
1. Readability & Maintenance: A missing `hashtag#include <stdio.h>` can be jarring for someone else reviewing your code. Optimizing is good, but not at the cost of clarity.
2. Universal Code? Maybe Not: Depending on specific function declarations might make your code less adaptable across different systems.
3. Risk of Errors: A wrong declaration can lead to undefined behavior, which can be catastrophic in embedded systems.
Whether you use the full header or just the declaration, the linker will attach the same library function’s binary code to your executable. This is because the call to printf in your C code translates to a call to the same location in the library, regardless of how you declared it.
Using just the declaration or the full header file might result in the same assembly for that particular function call, but the inclusion of a full header might bring in other macros, inline functions, or variable declarations that could affect other parts of your code or even the overall structure of the generated binary.
Moreover, just using a declaration means you’re relying on external knowledge about the function. If the function’s signature changes (though unlikely for standard library functions like printf), your code will break. Using the header file ensures you always have the most up-to-date declaration.
While selective declarations can be a boon for embedded applications, it’s crucial to balance the benefits against potential pitfalls. If you do take this path, remember: clear documentation is your best friend!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
An Article by: Yashwanth Naidu Tikkisetty
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
