an ambiguity in C89 which will never be fixed
sebsite.pw
sebsite.pw
I built this first as a 32-bit binary, and there was noise that I had to cut with a substr function.
In the rebuilding with my MinGW 64-bit Windows cross compiler on Oracle Linux, I had to mine function prototypes out of all the code for exactly this reason.
'for those unaware: c89 has a cool "feature" where, if you try to call a function which doesn't exist, rather than erroring out, the function is implicitly declared as a function with unspecified parameters returning int.'
I'm not testing this, because that is agony.
I'm leaving them a working build, and retiring this month.
This code was written by the living and the dead, and my stewardship is finished. I do not envy the poor soul who must test this.
It was ashes when I excavated it myself. A hat tip to those who have gone before.
Current GCC and clang error on them by default now, but that's a rather recent change.
The program that does this is called cproto and it was available back on comp.sources.unix as early as 1989 (if you find yourself with a time machine) and these days is available on nearly every Linux distro.
Also in 1989, mkproto from comp.sources.misc
http://ftp.fi.netbsd.org/pub/misc/archive/comp.sources.misc/...
Like almost without fail. I can’t even think of how you’d end up in a scenario like this because a compiler would complain before letting you use an undefined implicit declaration.
That's not possible for 'standard C' though, only for the separate language that's called "the common subset of C and C++". E.g. it works more or less by accident for some specific C code that predates C99, but even that is built with C++ semantics (which has many subtle and some not-so-subtle differences to C semantics).
Instead of trying to build C in C++ mode, turn all the warnings to 11 (and also include warnings that aren't in -Wall -Wextra, like -Wsign-conversion).
Best of luck, =3
One silly side effect of compiling C in C++ mode is that it forces you to cast from void pointers. E.g. the famous example of:
bla_t* bla = (bla_t*)malloc(sizeof(bla_t));
One critical missing piece of C compilation mode was usually that the compiler didn't warn when using a wrong enum type, but that's also fixed by now (assuming `-Wall -Wextra`, but that should always be enabled anyway, otherwise you're just flying blind), e.g.:
So yes, do not try to compile C code using a C++ compiler.
That you somehow get superior type checking with C++ is not really true anymore, as essentially all important parts were integrated into the C standard and the remaining should all exist as optional warnings in gcc. If you feel something is missing, please file a bug.
Given the Sealioning problem on YC, trying to remember an edge case issue from years ago would not go well. If your work habits aren't pushing into the compiler standards gray areas, than one probably won't ever encounter such issues. ymmv =3
Good C follows the 10 rules, uses old compatible macro language features, and is boring to trivially port. The "hold my beer" folks often go back to Python where the abstractions hide the foot-guns.
https://en.wikipedia.org/wiki/The_Power_of_10:_Rules_for_Dev...
The C++ compatibility with C, is "As Close as Possible to C, but no Closer", meaning supporting C should not break the stronger type checking or the improved type system C++ has over C.
As such, besides C89 original differences, compatibility has only been added for C features that don't clash with C++ approach to the same problem, and while the C++ standard library keeps up with ISO C, it also does so taking into consideration C++ features for the implementation of said library functions.
"Sibling Rivalry: C vs C++"
https://www.stroustrup.com/sibling_rivalry.pdf
"C and C++: Siblings"
https://www.stroustrup.com/siblings_short.pdf
"C and C++, a case for compatibility"
https://www.stroustrup.com/compat_short.pdf
Two examples of the library updates,
"C++17 should refer to C11 instead of C99"
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p00...
"C++26 should refer to C23 not C17"
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p33...
I’m not going to defend all of the ones C(++) has but stuff like deref’ing null or integer overflow or out of bounds access has its roots in sanity, it just looks insane today. There are tools for many/most of these and if you’re not using them you’re doing it wrong.
At the next meeting I nevertheless voted to accept the standard. (Being first in alphabetical order, I was the first person to ever do so.)
And it's not merely a "claim" -- are you actually suggesting that I'm lying? Your question doesn't even make sense as written, as my claim today could not have affected a decision in 1988. And "Not to judge, but" is a bizarre thing to say if one isn't judging. Your whole comment is rather rude.
Did the fact that I was the first to vote have an effect? Yes ... I was an outsider, having only joined the committee one meeting prior to the vote, and I really didn't know the general attitude of the committee members, so I didn't know how the vote would go, putting me in an awkward position. As it turned out, it was unanimous.
Oh, and I found documentation: https://www.open-std.org/JTC1/sc22/wg14/www/docs/n062.pdf -- the roll call lists Balter (me) first.
> In case you need to brush up on it
I have no such need.
> If it helps you, I meant it in the noun way not the verb way.
It doesn't help at all as it's a noun in both "your claim on first vote privilege" and "your claim that you voted first".
> not one definition on Merriam Webster contains doubt or accusation
You are quite mistaken. Both "to assert in the face of possible contradiction" (verb form) and "an assertion open to challenge" (noun form) very much "contains doubt".
Enough of this off topic discussion of grammar ... I won't respond again.
My guess is that the implicit declaration was a leftover from a C predecessor (B?) and kept in C to simplify programming in hybrid B/C environments. Just a guess though.
Obsolete standard turns out to be insufficiently strict, news at 11.
it may seem like a slightly more ridiculous claim, given the infamous features added in c99, although, in hindsight, every version after c89 was less C–like than the previous.
That's a nice bit of understated 90s design right there
The "nice" sites didn't style much at all, which usually meant the default serif font was used.
It is illegal to perform pointer arithmetic on function pointers. They are not necessarily interchangeable with data pointers. Clang is wrong.
Do you know what c89 does explicitly say is undefined? Any pointer arithmetic at all (or array subscripting) for pointers are not pointing to a member of an array. It's already invalid to do pointer arithmetic a pointer to a struct.
Not that it matters for this. This isn't doing pointer arithmetic, f is simply the identifier for the array of "sizeof(f) ints" that make up the function argument. The identifier is optional for a function declaration.
int f(int x) { return x + 1; }
int main(int argc, char *argv[]) {
int (*fp)(int) = f;
printf("Answer: %d\n", fp(39) + (****fp)(1));
return 0;
}The reason you can chain unlimited ''s is that f isn't actually a function pointer, it's a function designator. Function designators are automatically converted to function pointers in almost every case, but '' is special cased so that indirecting a raw function designator results in another function designator.
Edit: Actually on a closer reading, maybe it does. C89 doesn't explicitly point it out as forbidden or undefined, it simply defines two classes (objects and functions) and only defines a very limited set of valid operations on pointers to functions.
Though one operation that is implementation defined is converting a pointer to an int, and an int to a pointer. So with two steps through an implementation defined path, you have a data pointer to a function.
In some systems functions are smaller, since they're gate addresses in a jump table (who has more than 64k functions?), so that's no problem.
But in some systems functions are bigger, and PCDOS systems running in real mode this was very common, and in those cases you'd need to get the extra bits from someplace else (union trick), or just design things another way.
What are you thinking of?