What is your favorite C programming trick? (2009)

Re:What is your favorite C programming trick? (2009) by jcranmer on Sunday November 22, 2020 @11:38AM (#25178765)

I think what GP is referring to is C++ not supporting C's designated initializers, restrict qualifiers, or flexible array members features. These are roughly the only C features not in C++ that are worth supporting (the STL in C++ works better than VLAs, and templates work better than type-generic macros). All of the other new C features are either backported C++ features with different spellings, or new functionality (mostly library) that C++ adopts.

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Re:What is your favorite C programming trick? (2009) by pjmlp on Sunday November 22, 2020 @12:15PM (#25179068)

VLAs are gone, were made optional in C11, thus every compiler that jumped from C89 to C11 never bothered with them.

Google even sponsored a massive effort to clean the Linux kernel of their use.

A subset of designated initializers is supported in C++20.

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Re:What is your favorite C programming trick? (2009) by flohofwoe on Sunday November 22, 2020 @01:27PM (#25179667)

There's a surprising amount of perfectly valid C code that's not valid C++ (not even taking regrettable design warts like VLAs into account). The "common subset" of C and C++ is both a subset of C, and a subset of C++, e.g. C++ has forked C and turned its C subset into a non-standard dialect.

It's interesting that the other C descendant Objective-C has decided to "respect" its C subset instead of messing with it, with the result that new C standards are automatically supported in ObjC.

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Re:What is your favorite C programming trick? (2009) by pjmlp on Sunday November 22, 2020 @02:22PM (#25180200)

A descendant that would be dead by now wouldn't Apple decided to buy NeXT.

VLAs are dead, a broken design fixed in C11 by removing it from the standard, no idea why everyone keeps referring to them.

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Re:What is your favorite C programming trick? (2009) by yakubin on Sunday November 22, 2020 @12:47PM (#25179354)

> A subset of designated initializers is supported in C++20.

Took them only 21 years... And this standard being so recent, most projects won't have that for years to come.

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Re:What is your favorite C programming trick? (2009) by pjmlp on Sunday November 22, 2020 @01:13PM (#25179546)

Doesn't matter, the point was what C subset does C++ support today.

https://godbolt.org/z/GW59rM

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Re:What is your favorite C programming trick? (2009) by vitus on Sunday November 22, 2020 @06:22PM (#25182043)

C++20 designated initializers must be specified in definition order, whereas they don't in C99.

In your example,

    Point point = {.z = 2.0, .x = 1.0};

produces a compilation error. This is annoying, but workable. And at least it's a compile-time error, rather than a bug that perniciously sneaks into production.

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Re:What is your favorite C programming trick? (2009) by pjmlp on Monday November 23, 2020 @02:03AM (#25184236)

Why do you think I wrote "A subset of designated initializers is supported in C++20."?

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Re:What is your favorite C programming trick? (2009) by saagarjha on Monday November 23, 2020 @03:48AM (#25184795)

The one good use of VLAs I know of is casting a buffer into a multidimensional (variable-length) array to allow for subscripting to work.

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Re:What is your favorite C programming trick? (2009) by pjmlp on Monday November 23, 2020 @04:00AM (#25184858)

Whatever good uses VLAs might actually have had, they are gone with C11.

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Re:What is your favorite C programming trick? (2009) by saagarjha on Monday November 23, 2020 @04:05AM (#25184896)

Well, they're a conditional feature now, you are supposed to check __STDC_NO_VLA__.

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Re:What is your favorite C programming trick? (2009) by pjmlp on Monday November 23, 2020 @10:26AM (#25187683)

Which basically means that outside gcc and clang based compilers, __STDC_NO_VLA__ will be false, for example on MSVC or IAR Embedded Workbench.

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