If C didn't have (as much) undefined behavior it would be practically perfect. There's not much else that I would change about it.
It's much too easy to produce buffer overflows in C, be it due to the design of C strings or just because of the manual handling of dynamic memory.
The big difference was that those OSes versus UNIX costed real money.
Any idea why there was no popular safe array or safe string library for C? Maybe at that time there was no internet and everyone had to create his own abstractions?
Bell Labs was forbidden to sell their research, so they offered UNIX for a symbolic price to universities (vs what other OS used to cost), alongside source code tapes and a liberal license.
This gave birth to several startups that tried to create a business using UNIX instead of the alternatives, given the authors experience with UNIX at the university, e.g. Sun and SGI among others.
Later when the US goverment dictated AT&T split, AT&T was allowed to charge for UNIX and that is when they decided to go after BSD, because 10 years later, under such conditions, UNIX was slowing eating mainframes, given the success of Sun, SGI, Aix, ....
There are no safe array or safe string libraries, because they all fall appart under scrutiny, given C's approach to secure code.
I do not understand, maybe give an example.
About the history I am not sure that proves that UNIX and C advantage was only because of that, it could be a factor but there are merits to C and UNIX that if you want to disprove you can;t just do it by mentioning that history. I mean Windows API used C.
Because since those libraries are not built-in types, you always need to convert back to a ptr and length values at some point when interoperating with other C code.
And given the lack of bounds checking, you are back at square one.
> I mean Windows API used C.
Windows API used C, because by the time Windows came around UNIX was already well established in the enterprise.
C spread outside UNIX, because many of us were using C dialects, e.g. Small-C, on personal computers when bringing work home from job/university.
And that's exactly why C wins, in my opinion. Because that means interoperability.
Storing a pointer + length pair in a fixed layout struct is bad from a normalization standpoint. They are independent data. If you don't separate them you will end up with data redundancies as soon as you have parallel arrays. If you use dynamic vectors and in C++ or similar languages and you ask yourself which is the object that you should call .size() on, that's when you notice that it's morally wrong to bundle pointer + length.
Or more precisely, 68% of Linux kernel exploits according to Google's talk at Linux Kernel Summit 2018.
You can't rip them out and replace them with something better without massive code legacy issues. And then you still haven't dealt with other sources of buffer overflows in C.
> After publishing the Friendly C Proposal, I spent some time discussing its design with people, and eventually I came to the depressing conclusion that there’s no way to get a group of C experts — even if they are knowledgable, intelligent, and otherwise reasonable — to agree on the Friendly C dialect. There are just too many variations, each with its own set of performance tradeoffs, for consensus to be possible.
Because making C safer would introduce a lot more complexity in the runtime environment and instrumentation, and that is even hard to achieve correctly or has varying performance implications across all ISAs that C compilers are currently targeting.
Consider out of bounds indexing. To determine that an instruction is touching a memory region that is not, in abstract terms, a C array or a memory allocation by malloc and friends, now you need to insert long traps in memory, and even then, there is nothing stopping you from accessing array `b` through, for example, `a + 42`.
I don't understand the "undefined behavior" bandwagon.
1. We have a perfectly defined list of "undefined behaviors".
2. Said list also happens to be relatively small and scoped.
3. "Undefined behaviors" exist because the language can't make certain runtime guarantees which are largely dependent on compiler/os/platform/hardware-specific promises. If you have to, just roll in your own runtime checks. C won't force those on you...
Or evaluation order - `i = ++i;` could easily be defined in some way. But might prevent some niche optimisations by the compiler.
Of course by C's nature there are limits (C won't be able to detect use after free or similar without changing language notably) but there is room where UB could be reduced, if it was seen as neccisary.
> "Of course by C's nature there are limits"
You seem to acknowledge the fact that most of the undefined behaviors in C are essentially born out of compromise. Those compromises were driven by principles such as "keep the power in the hands of developers", "don't impose unnecessary restrictions", "keep the language clean", "avoid hidden runtime magic". The end results reflect that.
As I've mentioned in my previous comment, there's no "one size fits all", so the language makes it trivial for you to roll out your very own runtime magic (à-la Zig/Nim) which suits you best. Why is that a bad thing?
An easier approach would be to put a bound on what is permissible undefined behavior.
Sounds a bit like an oxymoron, doesn't it? After all, it is "undefined", right?
However, the C standard does exactly that!
Permissible undefined behavior ranges from ignoring the situation completely with unpredictable results, to behaving during translation or program execution in a documented manner characteristic of the environment (with or without the issuance of a diagnostic message), to terminating a translation or execution (with the issuance of a diagnostic message).
(section 3.4.3)
In fact, in the first version of the ANSI/ISO C standard, this was a binding part of the standard. In later versions, it was made non-binding, though the language is still in the standard.
Yes, the standard has language that says what permissible undefined behavior is, but you are free to ignore it and still call yourself compliant. Which is what just about everybody does nowadays.
Make it binding again and most of the mess disappears.
https://blog.metaobject.com/2018/07/a-one-word-change-to-c-s...
Setting "the compiler" = "the environment" and therefore anything the compiler does is part of the environment and thus legit seems at best the type of sleight of hand the compiler writers use to justify their actions.
When defining the behaviour of the compiler, "the environment" obviously cannot be "the compiler".
It's a lot of work.
> Is such a thing impossible? Have people done it?
It's possible; Ada has a really good take -- in that standard, there's a class of errors called "bounded errors" which on the surface look like "undefined behavior", but are a lot different in that they list out the possible results and thus preclude the "nose demons" problem of C -- see: http://www.ada-auth.org/standards/2xaarm/html/AA-1-1-5.html