6 ms·

Wow, I didn't know this was valid C code, it's pretty convenient. school_t uiuc = { .school = "University of Illinois at Urbana-Champaign", .lo

by Aldo_MX 12y ago

Wow, I didn't know this was valid C code, it's pretty convenient. school_t uiuc = { .school = "University of Illinois at Urbana-Champaign", .location = "Urbana, IL", .program = "BS Computer Science", .started = 1251158400, .left = 1336608000, .accomplishments = { "Minor in International Studies in Engineering, Japan", "Focused on systems software courses", NULL } };

lcampbell 12y ago
It's a C99 feature (I think?) -- designated literals. They're absolutely wonderful.
- amaterasu 12y ago
  It's supported by GCC as an extension to C90 too.
  - samatman 12y ago
    what does that even mean? Isn't C99 an extension of C90/ANSI? Doesn't GCC support the whole of C99 as an extension to ANSI?
    - masklinn 12y ago
      It means that GCC will allow/support this even if you set it to std=c89 or std=c90.
      - michaelmior 12y ago
        Won't that only be supported in gnu89 or gnu90 mode?
        edmccard 12y ago
        No, it will be supported using -std=c89 or -std=90, unless you also specify -pedantic.
        michaelmior 12y ago
        Yes, I realized after posting that -pedantic is required for strict standards compliance.
        mikeash 12y ago
        The GNU modes just enable additional features which conflict with plain C. Any feature which can coexist with plain C will be enabled in the regular C modes too. For example, __typeof__ is enabled everywhere, because the compiler is allowed to do just about anything it wants with a __ prefix, but plain typeof is only enabled in the GNU modes, since it could cause valid C programs using "typeof" for their own purposes to fail to compile.
    - dhekir 12y ago
      C99 is not a strict extension, but as stated in its foreword, "this second edition [C99] cancels and replaces the first edition [C90]". For instance, implicit function declarations are allowed in C90 but not in C99.
- masklinn 12y ago
  Although GP didn't remark on it, TFA uses an other cool feature which is actually C11: anonymous unions. Although not as wonderful as designated literals, they're really quite convenient.
- blt 12y ago
  I so, so wish C++ would adopt this feature.
- stephencanon 12y ago
  Designated initializers are one of a few indispensable features that make "C++ is a better C" a complete non-starter for me.
zem 12y ago
i learnt about them from this post and the library it refers to: http://spin.atomicobject.com/2014/10/08/c99-api-designated-initializer/ http://spin.atomicobject.com/2014/10/08/c99-api-designated-i... good read, both the post and the socket99 code.
amitlan 12y ago
My gcc required me to put { } around any fields of unnamed unions. [gcc version 4.4.7 20120313 (Red Hat 4.4.7-11) (GCC)]
- GFK_of_xmaspast 12y ago
  gcc 4.4 is getting kind of long in the tooth.
cipher0 12y ago
These are called desginated initializers, they're part of C99.[0] This is a good read which discusses them and also devles into compound literals.[1] [0] https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html [1] https://nickdesaulniers.github.io/blog/2013/07/25/designated-initialization-with-pointers-in-c/ https://nickdesaulniers.github.io/blog/2013/07/25/designated...
wschroed 12y ago
I highly recommend "21st Century C" (http://shop.oreilly.com/product/0636920025108.do http://shop.oreilly.com/product/0636920025108.do) as a tour of modern C programming, including use of C99 features. It goes over C tooling (profiling, debugging, testing, cross-platform deployment), and explores C99.
- pwaring 12y ago
  There's a newer edition available which has been published recently: http://shop.oreilly.com/product/0636920033677.do http://shop.oreilly.com/product/0636920033677.do
- Aldo_MX 12y ago
  Following your recommendation, to people interested in learning about Modern C++, Stroustrup's Tour of C++ is a recommended read. http://www.stroustrup.com/Tour.html http://www.stroustrup.com/Tour.html
pwaring 12y ago
They're used heavily in Linux device drivers, amongst other things - here's just one example: https://github.com/torvalds/linux/blob/master/drivers/video/fbdev/vfb.c#L126 https://github.com/torvalds/linux/blob/master/drivers/video/...

by Aldo_MX 12y ago

lcampbell 12y ago

It's a C99 feature (I think?) -- designated literals. They're absolutely wonderful.

amaterasu 12y ago
It's supported by GCC as an extension to C90 too.
- samatman 12y ago
  what does that even mean? Isn't C99 an extension of C90/ANSI? Doesn't GCC support the whole of C99 as an extension to ANSI?
  - masklinn 12y ago
    It means that GCC will allow/support this even if you set it to std=c89 or std=c90.
    - michaelmior 12y ago
      Won't that only be supported in gnu89 or gnu90 mode?
      - edmccard 12y ago
        No, it will be supported using -std=c89 or -std=90, unless you also specify -pedantic.
        michaelmior 12y ago
        Yes, I realized after posting that -pedantic is required for strict standards compliance.
      - mikeash 12y ago
        The GNU modes just enable additional features which conflict with plain C. Any feature which can coexist with plain C will be enabled in the regular C modes too. For example, __typeof__ is enabled everywhere, because the compiler is allowed to do just about anything it wants with a __ prefix, but plain typeof is only enabled in the GNU modes, since it could cause valid C programs using "typeof" for their own purposes to fail to compile.
  - dhekir 12y ago
    C99 is not a strict extension, but as stated in its foreword, "this second edition [C99] cancels and replaces the first edition [C90]". For instance, implicit function declarations are allowed in C90 but not in C99.
masklinn 12y ago
Although GP didn't remark on it, TFA uses an other cool feature which is actually C11: anonymous unions. Although not as wonderful as designated literals, they're really quite convenient.
blt 12y ago
I so, so wish C++ would adopt this feature.
stephencanon 12y ago
Designated initializers are one of a few indispensable features that make "C++ is a better C" a complete non-starter for me.

zem 12y ago

i learnt about them from this post and the library it refers to: http://spin.atomicobject.com/2014/10/08/c99-api-designated-initializer/ http://spin.atomicobject.com/2014/10/08/c99-api-designated-i... good read, both the post and the socket99 code.

amitlan 12y ago

My gcc required me to put { } around any fields of unnamed unions. [gcc version 4.4.7 20120313 (Red Hat 4.4.7-11) (GCC)]

GFK_of_xmaspast 12y ago
gcc 4.4 is getting kind of long in the tooth.

cipher0 12y ago

These are called desginated initializers, they're part of C99.[0] This is a good read which discusses them and also devles into compound literals.[1] [0] https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html [1] https://nickdesaulniers.github.io/blog/2013/07/25/designated-initialization-with-pointers-in-c/ https://nickdesaulniers.github.io/blog/2013/07/25/designated...

wschroed 12y ago

I highly recommend "21st Century C" (http://shop.oreilly.com/product/0636920025108.do http://shop.oreilly.com/product/0636920025108.do) as a tour of modern C programming, including use of C99 features. It goes over C tooling (profiling, debugging, testing, cross-platform deployment), and explores C99.

pwaring 12y ago
There's a newer edition available which has been published recently: http://shop.oreilly.com/product/0636920033677.do http://shop.oreilly.com/product/0636920033677.do
Aldo_MX 12y ago
Following your recommendation, to people interested in learning about Modern C++, Stroustrup's Tour of C++ is a recommended read. http://www.stroustrup.com/Tour.html http://www.stroustrup.com/Tour.html

pwaring 12y ago

They're used heavily in Linux device drivers, amongst other things - here's just one example: https://github.com/torvalds/linux/blob/master/drivers/video/fbdev/vfb.c#L126 https://github.com/torvalds/linux/blob/master/drivers/video/...