What techniques can you use to reduce code size in C/C++ for embedded systems?

1 Use compiler options

Reducing code size can be achieved by using the correct compiler options. Different compilers offer varying options, such as optimization level, which can improve the speed or size of the code. However, higher optimization levels may impact readability, debugging, or accuracy. Debug information is also important to consider as it increases code size but helps with debugging. Function inlining is another option that can improve performance, but it too increases code size. You can use inline keywords or attributes to suggest or prevent function inlining for specific functions.

2 Use data types wisely

Reducing code size is possible by using data types wisely. Data types affect the amount of memory allocated for variables, constants, and structures. To achieve this, use the smallest data type that can hold the range of values needed. For instance, char instead of int if 8 bits are enough. Enums are also a good choice for symbolic values as they are stored as integers which are usually smaller than strings or floating-point numbers. Bit fields and bit masks are useful for flags or status bits as they allow packing multiple boolean values into a single byte or word, saving space and memory access time. Finally, const and static qualifiers should be used for variables that do not change or are only used in one file. This tells the compiler to store them in read-only memory or eliminate them from the global symbol table, thus reducing code size and memory usage.

3 Use code patterns and libraries

Reducing code size in C/C++ for embedded systems can be achieved through the use of code patterns and libraries. Reusable pieces of code can simplify logic, avoid duplication, and leverage existing functionality. For instance, loops, functions, and macros can help write concise and maintainable code while eliminating redundant instructions; switch-case statements are more efficient than if-else chains; and standard or third-party libraries can provide optimized and tested code for tasks or algorithms. These techniques can improve memory usage, performance, power consumption, and reliability. What other techniques do you use to reduce code size in C/C++ for embedded systems? Share your tips and tricks in the comments below.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?