Comment by ironmagma
4 years ago
Shouldn’t we just come clean and admit to ourselves that there is no such thing as the C standard? There is a collection of loosely related languages that look similar and that collectively we call C, but really they’re all completely different and share almost no interoperability or common characteristics. And those standards that do exist provide almost no ability to reason about your code including things like ordering of statements.
No, that's complete nonsense.
Here's the latest revision of the standard: https://www.iso.org/standard/74528.html
C has had a well-defined memory model since C11, I believe (re: "ordering of statements").
> ISO-C11 specifies 203 circumstances that cause undefined behaviors.
203 is enough to make almost every line of code questionable. The result of this is that looking at a simple 3 line C program and being asked whether the program terminates is undecidable without knowing which compiler was used.
Null dereference for example is undefined behavior, and could cause a termination or not, depending on the implementation, even if it is known to be standards conforming to C11.
[1] https://resources.tasking.com/p/undefined-behaviors-iso-c-th...
> 203 is enough to make almost every line of code questionable. The result of this is that looking at a simple 3 line C program and being asked whether the program terminates is undecidable without knowing which compiler was used.
This is hyperbole to the point of being nonsensical.
> Null dereference for example is undefined behavior, and could cause a termination or not, depending on the implementation, even if it is known to be standards conforming to C11.
This sentence doesn't make any sense. If your C code has UB, it is wrong. The behavior of particular environments around certain UB is irrelevant to standards-conforming code, because standards-conforming code doesn't have UB.
9 replies →
A good argument for compiling your debug builds with "-fsanitize=undefined".
2 replies →
There is a standard, sure. But there are also a lot of compilers out there and I would bet that all but a few has either a "this compiles c11 except for [list of unimplemented features]" caveat or non-standard extensions.
> But there are also a lot of compilers out there and I would bet that all but a few has either a "this compiles c11 except for [list of unimplemented features]" caveat or non-standard extensions.
Your statement is broadly reasonable. Here's the GP:
> Shouldn’t we just come clean and admit to ourselves that there is no such thing as the C standard? There is a collection of loosely related languages that look similar and that collectively we call C, but really they’re all completely different and share almost no interoperability or common characteristics. And those standards that do exist provide almost no ability to reason about your code including things like ordering of statements.
It's just a string of incorrect statements, or at best, extreme hyperbole.
1. There is a C standard.
2. There's only one C language. Implementations differ, but not "completely," and are mostly interoperable. They all have in common the standard language, of course.
3. The C standard provides a fairly strong mental model for reasoning about code. Especially in later revisions, but even in C99. "Almost no ability to reason about" is false.
If you think C is fragmented or difficult to reason about, let me introduce you to Python (Python3, Jython, PyPy), Java (Oracle, OpenJDK, Dalvik), C# (Mono, .NET Core, .NET on Windows...), C++ (if you think implementing C99-C18 is hard, check out the stdlib required by modern versions of C++), etc.
4 replies →