Also, signed overflow being undefined rather than defined as wrapping means that more secure implementations where it traps are permitted. Passing -fsanitize=signed-integer-overflow -fsanitize-trap=signed-integer-overflow is standards compliant and used for hardening in AOSP.
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Trapping on overflow breaks lots of code that does it on purpose. Code that can’t run is more secure than code that doesn’t only in a meaningless sense.
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That code can be fixed and the fixes are clear cut bug fixes. High quality C code is tested with ASan, TSan, UBSan, etc. and many of these issues are already being caught and fixed over time. Portable and safe C code needs to avoid relying on undefined behavior like this.
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You say overflow is undefined. I say it’s defined. As a bonus CPUs say I’m right. The world needs a language that just does what the CPU does. If you don’t want that, don’t program in C.
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C isn't defined as that language, and you're not in a position where you get to define the language. In the real world, C is deployed with various safety features taking advantage of many things being undefined and reducing portability / compatibility with those wouldn't be good.
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Neither of us gets to choose how C is defined. You want to make it more permissive, and I would make it stricter and safer. Instead, the standard compromises between all the competing interests (portability, performance, safety) by giving implementations lots of freedom.
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The standard creates a mess by compromising too broadly. I’m not arguing with you over what anyone is in a position to do, so that point is moot. I am proposing a standard that would make it possible to write systems code and have confidence in what it does.
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Okay, and that's not how C is defined or how it's likely to ever be defined. You're free to make a standard for your own language based on C. I don't think what the world needs is a memory and type unsafe language that's even more permissive, but you're free to make one.
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It’s not “more permissive”. Making something undefined doesn’t make it unpermitted.
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Yes, it does make it more permissive. You want to forbid implementations of C that trap on out-of-bounds accesses, signed overflow, etc. which is currently permitted by the standard and widely deployed in production systems in the real world to improve safety and security.
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You want to forbid memory tagging (SPARC ADI, ARM MTE), shadow stacks, type-based CFI and even very basic security features like _FORTIFY_SOURCE in fully standards compliant implementations of C. Expanding what C language allows in well-defined code is making it more permissive.