IIRC, MSVC stubbornly refuses to add support for variable-length arrays (which AFAIK are required for full C99 support). I don't know if there's anything else on that list of C99 features that MSVC doesn't support yet.
You are correct that VLAs are mandatory for C99, but they turned out to be such a bad idea that they are optional in C11 onwards.
> I don't know if there's anything else on that list of C99 features that MSVC doesn't support yet.
IIRC, MSVC's `snprintf` and friends are broken (returns incorrect values and/or interprets the size parameter incorrectly). I think all of the annexure K stuff is broken in MSVC.
Google has paid the development effort for the Linux kernel to get rid of all VLA occurrences.
> Google has paid the development effort for the Linux kernel to get rid of all VLA occurrences.
IIRC, what they were really interested in getting rid of was not the normal VLA we're talking about, but something even more esoteric called VLAIS (variable length arrays in structures), which clang didn't support. See https://lwn.net/Articles/441018/ for a discussion about that.
I dunno how to probe the stack in standard C, and so I never used VLAs, nor allowed them because (I thought that) there was no way to determine if a VLA declaration would cause a stack overflow.
Doesn’t annex k only exist in MSVC because it’s a bunch of crap MS got the committee to add and no one else wanted to implement?
And isn’t it a C11 thing?
Yes, but in a perverse twist of fate, Microsoft's implementation does not conform.
> And isn’t it a C11 thing?
I stand corrected, it is a C11 thing.
They were made optional in C11. It was a good decision because it's a dangerous misfeature.
That's how it's implemented in all the major compilers. Anyway, even a hypothetical heap-based implementation would be bad because there's no way to report allocation errors.
// VLA
int foo(int n) { int array[n]; }
// flexible array member
struct s { int n; double d[]; }; struct s s1 = malloc(sizeof (struct s) + (sizeof (double) 8));
I don't need a lecture. I have actually lectured on C before.
I do have them bucketed similarly in my mind. They are both c99 features about variable sized arrays. MS has not implemented either one iirc.
Flexible array members were implemented a long time ago. The oldest Visual C++ I have at hand is 2005 and it already has them (although only in C mode).
There is a Blog from Raymond on this[1]. The TL;DR: is that zero length arrays and FAMs weren't legal until C99. Not sure where the support from MSVC factors in. But that's the story and AFAIK he's sticking too it.
[1] https://devblogs.microsoft.com/oldnewthing/20040826-00/?p=38...