CompCert
Shares rank 10 of 18 c compilers by recommenders
Formally verified C compiler trusted for safety-critical code and fast native output. Critics report a wrong-output bug and code worse than gcc -O0.
Formally verified C compiler trusted for safety-critical code and fast native output. Critics report a wrong-output bug and code worse than gcc -O0.
11 people gave an opinion
- recommend it
- 9
- criticize it
- 2
- approval share
- 82%
Recommended in 8 of 13 months
- November 2025: not recommended
- December 2025: recommended
- January 2026: recommended
- February 2026: recommended
- March 2026: not recommended
- April 2026: recommended
- May 2026: not recommended
- June 2026: recommended
- July 2026: recommended
- August 2026: recommended
- September 2026: not recommended
- October 2026: recommended
- November 2026: not recommended (month in progress)
Why it doesn’t carry the badge
- 9 people recommend itNeeds 10 or more, not met.
- 4.5 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 8 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Proven correct compiler
“Check out seL4 and CompCert for real-world examples of complex software proven correct and used in industry.”
Comment from 30 Jun 2026 in “You Don't Know Jack About Formal Verification” “the hard part of compiler correctness is already handled by the efforts of CompCert”
Comment from 17 Jan 2026 in “Lies, Damned Lies and Proofs: Formal Methods Are Not Slopless” “a proven correct C compiler used by Airbus and others for real production software”
Comment from 31 Jul 2026 in “Logic for Programmers by Hillel Wayne” - Comment from 15 Jul 2026 in “RISC-V Is Inevitable: State of the Union Keynote Argues”
- Comment from 31 Jul 2026 in “Why Don't People Use Formal Methods?”
Used in safety-critical industry
“It's the actual way that companies that have large C code bases in safety-critical industries verify their code.”
Comment from 9 Oct 2026 in “Reducing undefined behavior in the C language” “a proven correct C compiler used by Airbus and others for real production software”
Comment from 31 Jul 2026 in “Logic for Programmers by Hillel Wayne” “a proven correct C compiler used by Airbus”
Comment from 31 Jul 2026 in “Why Don't People Use Formal Methods?” Example of verified software
“Check out seL4 and CompCert for real-world examples of complex software proven correct and used in industry.”
Comment from 30 Jun 2026 in “You Don't Know Jack About Formal Verification” “CompCert is an example of how to do this.”
Comment from 20 Aug 2026 in “The Case Against Formal Verification, 50 Years Later”
Other c compilers people recommend
The four most recommended other c compilers, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| Fil-C | 160 | 60 | 73% | 13 | — | Approved |
| Claude's C Compiler | 39 | 83 | 32% | 5 | — | — |
| Visual C++ | 29 | 17 | 63% | 12 | — | — |
| Tiny C Compiler (TCC) | 22 | 3 | 88% | 9 | — | Approved |
| CompCertThis page | 9 | 2 | 82% | 8 | — | — |
What people said
15 of the 17 comments that mention it, newest first. Each links to the original comment.
“CompCert produces surprisingly fast native code.”
“It's the actual way that companies that have large C code bases in safety-critical industries verify their code.”
“Not even spec tests and compcert.”
“CompCert is an example of how to do this.”
“produces really bad code, below the level of gcc -O0”
“Subsequent high volume random testing with Csmith found no bugs in the formally verified section”
“a proven correct C compiler used by Airbus”
“a proven correct C compiler used by Airbus and others for real production software”
“use a formally proven toolchain like compcert to compile it”
“Check out seL4 and CompCert for real-world examples of complex software proven correct and used in industry.”
“By staying true to constructive logic, there was a lot of progress”
“Then, we have both a precise semantics and tools to help produce robust output.”
“the hard part of compiler correctness is already handled by the efforts of CompCert”
“a formally verified C compiler generates incorrect output because of an inconsistent value in”
“You've likely trusted your life to compcert.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.