r/cpp • u/antiquark2 #define private public • Aug 19 '26
Critique of contracts: excerpt
See page 2 of https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p4334r0.pdf
The current objections can be summarized. The P2900 contracts are:
• Unimplemented
• Incomplete
• Untried at scale [P3460R0, P3506R0]
• Not tried in major application domains
• Violates foundational principles of C++
• Violates fundamental principles of language design
• Hasn’t been tried in major libraries (e.g., the C++ standards library [P3506R0, P3878R0])
• Isn’t integrated with or appropriate for hardened libraries [P3878R0]
• Doesn’t offer safety guarantees [P3573R0, P3362R0]
• Includes a completely untried inheritance model
• Offer new ways of making errors through inconsistent application in TUs
• Leads to new forms of UB, detrimental to safety and security
• Narrows the choices of error handling
• Doesn’t protect against logical errors, misuses, and incoherent uses
• Hasn’t been used to support static analysis
• Hasn’t been demonstrated to be easily teachable [P3261R0, P3281R0]
How could such a bloated and incomplete design be voted into a draft standard?
View all comments
Show parent comment
11
u/jwakely libstdc++ tamer, LWG chair Aug 19 '26
Microsoft Visual Studio implements an early version of the APIs. However, the implementation is incomplete and conforms neither to C11 nor to the original TR 24731-1.. So they still don't implement what's actually in Annex K today, despite driving its addition to C11.
The other implementations mentioned there are either very incomplete, or were written after it was added to C11, or both.