CCC vs GCC – Harshanu February 8, 2026 CCC vs GCC Posted on February 8, 2026 • 15 minutes • 3024 words Introduction Anthropic recently published a blog post about building a C compiler entirely with Claude . They called it CCC (Claude’s C Compiler) and claimed it could compile the Linux kernel. 100% of the code was written by Claude Opus 4.6, a human only guided the process by writing test cases. That sounded interesting enough to test the claim and benchmark CCC against the industry standard GCC. The source code of CCC is available at claudes-c-compiler . It is written entirely in Rust, targeting x86-64, i686, AArch64 and RISC-V 64. The frontend, SSA-based IR, optimizer, code generator, peephole optimizers, assembler, linker and DWARF debug info generation are all implemented from scratch with zero compiler-specific dependencies. That is a lot of work for an AI to do. What is a Compiler, Assembler and Linker? Before we jump into the comparison, it helps to understand what happens when you compile a C program. There are four stages involved. Image credit: The four stages of the gcc compiler Preprocessor : Handles #include , #define and other directives. It takes the source code and produces expanded source code. Compiler : Takes the preprocessed source code and translates it into assembly language. This is where the real heavy lifting happens, understanding the C language, type checking, optimizations, register allocation and so on. Assembler : Converts the assembly language into machine code (object files). It has to know the exact instruction encoding for the target CPU architecture. Linker : Takes one or more object files and combines them into a single executable. It resolves references between files, sets up memory layout and produces the final binary. Why Compilers Are Beasts Writing a programming language is hard (prior vibe coding). Writing a compiler is on another level entirely. A programming language defines the rules. A compiler has to understand those rules, translate them into machine instructions, optimize the output for speed and size, handle edge cases across different CPU architectures and produce correct code every single time. GCC has been in development since 1987. That is close to 40 years of work by thousands of contributors. It supports dozens of architectures, hundreds of optimization passes and millions of edge cases that have been discovered and fixed over the decades. The optimization passes alone (register allocation, function inlining, loop unrolling, vectorization, dead code elimination, constant propagation) represent years of PhD-level research. This is one of the reasons why it’s ubiquitous. This is why CCC being able to compile real C code at all is noteworthy. But it also explains why the output quality is far from what GCC produces. Building a compiler that parses C correctly is one thing. Building one that produces fast and efficient machine code is a completely different challenge. Why the Compiler Is the “E

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