How Can I Significantly Reduce C Compilation Times?

Optimizing C Compilation Times

Compilation times in C can be a significant roadblock in development. Fortunately, numerous techniques exist to expedite this process.

Language Techniques

• Pimpl Idiom: Separating implementation details from public headers using opaque pointers improves exception safety and reduces recompilation.
• Forward Declarations: Declaring variables without defining them minimizes the amount of required compilation. Avoid including complete definitions in headers.
• Guard Conditions: Implement preprocessor macros like #pragma once/ifndef to prevent multiple inclusions of the same header file in a translation unit.

Compiler Options

• Precompiled Headers: Cache frequently included headers once to reduce subsequent recompilations.
• Parallelism: Harness multiple cores/CPUs for simultaneous compilation using compiler options like -j in GNU Make or /MP in Visual Studio.
• Lower Optimization Level: Adjust compiler optimization settings to trade performance for reduced compilation time.
• Shared Libraries: Move code into separate libraries to reduce compile and linking time for seldomly modified portions.

External Methods

• ccache: Utilize a caching utility to store and reuse intermediate compilation results.
• Parallel Compilation Tools: Leverage dedicated tools like Incredibuild, Unity Build, or distcc for distributed compilation.
• Hardware Upgrades: Invest in faster computers with ample RAM, SSDs, and multiple CPU cores/threads.

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