Comments on: 7.14 — Ellipses (and why to avoid them) http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/ Thu, 09 Sep 2010 12:59:21 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: Bob http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-91403 Bob Sat, 04 Sep 2010 20:44:16 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-91403 Or he should add a report spam button, or even a "vote spam" so if Alex isn't around people can vote spam off and wait for admin approval. Or he should add a report spam button, or even a “vote spam” so if Alex isn’t around people can vote spam off and wait for admin approval.

]]> By: twilight http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-66647 twilight Wed, 19 Aug 2009 12:17:29 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-66647 oh, how nice you are... and we even know what exactly it is you are upset about... oh, how nice you are… and we even know what exactly it is you are upset about…

]]> By: baldo http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-66475 baldo Mon, 17 Aug 2009 15:41:16 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-66475 Hey Alex, I suggest cleaning many of the spam or useless comments because they clutter the rest of comments that are really useful. Thanks! Hey Alex, I suggest cleaning many of the spam or useless comments because they clutter the rest of comments that are really useful. Thanks!

]]> By: Gates Bill http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-64790 Gates Bill Wed, 22 Jul 2009 17:34:26 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-64790 Fuck you Fuck you

]]> By: a http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-60230 a Fri, 08 May 2009 02:50:52 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-60230 "Consequently, the first call to va_arg will only read the first 4 types of the double (producing a garbage result), " shouldn't that read "first 4 <i>bytes</i>"? “Consequently, the first call to va_arg will only read the first 4 types of the double (producing a garbage result), ”

shouldn’t that read “first 4 bytes“?

]]> By: Alex http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-59745 Alex Sat, 02 May 2009 04:37:51 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-59745 Yeah, I didn't want to encourage people to try to clone printf(). Yeah, I didn’t want to encourage people to try to clone printf().

]]> By: Ben http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-55321 Ben Thu, 02 Apr 2009 10:16:36 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-55321 I think it might be worth mentioning the ellipses' value in formatted-string functions such as the printf() family. It would be ideal for implementing a date() function similar to that in PHP, for instance, where the number and type of parameters is explicitly defined in the format string. Obviously this is also dangerous (possibly even more so) but it would demonstrate handling mixed-type variable arguments. Of course it might also demonstrate How To Break Your Stack (TM). I think it might be worth mentioning the ellipses’ value in formatted-string functions such as the printf() family.
It would be ideal for implementing a date() function similar to that in PHP, for instance, where the number and type of parameters is explicitly defined in the format string. Obviously this is also dangerous (possibly even more so) but it would demonstrate handling mixed-type variable arguments. Of course it might also demonstrate How To Break Your Stack (TM).

]]> By: Learn C++ - » 15.4 — Uncaught exceptions, catch-all handlers, and exception specifiers http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-30974 Learn C++ - » 15.4 — Uncaught exceptions, catch-all handlers, and exception specifiers Sat, 25 Oct 2008 20:07:40 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-30974 [...] it uses the ellipses operator (…) as the type to catch. If you recall from lesson 7.14 on ellipses and why to avoid them, ellipses were previously used to pass arguments of any type to a function. In this context, they [...] [...] it uses the ellipses operator (…) as the type to catch. If you recall from lesson 7.14 on ellipses and why to avoid them, ellipses were previously used to pass arguments of any type to a function. In this context, they [...]

]]> By: Learn C++ - » 7.13 — Command line arguments http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-13498 Learn C++ - » 7.13 — Command line arguments Tue, 29 Apr 2008 05:08:28 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-13498 [...] « 12.6 — Pure virtual functions, abstract base classes, and interface classes | Home | 7.14 — Ellipses (and why to avoid them) » Friday, February 15th, 2008 at 4:06 [...] [...] « 12.6 — Pure virtual functions, abstract base classes, and interface classes | Home | 7.14 — Ellipses (and why to avoid them) » Friday, February 15th, 2008 at 4:06 [...]

]]> By: Alex http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/comment-page-1/#comment-10293 Alex Mon, 24 Mar 2008 22:34:29 +0000 http://www.learncpp.com/cpp-tutorial/714-ellipses-and-why-to-avoid-them/#comment-10293 My understanding (and I may be wrong about this) is that the implemention of va_start() and va_args() is left up to the compiler. If that's actually the case, then va_end() could do any necessary cleanup. I looked at how va_end() was implemented in Microsoft Visual Studio and this is how it is defined: <pre> #define va_end(ap) ap = (va_list)0 </pre> As you can see, it's actually a macro function that just sets the ap parameter to 0. So, at least with Microsoft Visual Studio, there's no real practical effect of calling va_end(), outside of maybe NULLing your list in case you inadvertently try to use it again without calling va_start(). In your example, you'd have to pass list into va_end(), but va_start() should cause the list to start at the beginning of the ellipses again -- so yes, nX would be the first element of the ellipses. My understanding (and I may be wrong about this) is that the implemention of va_start() and va_args() is left up to the compiler. If that’s actually the case, then va_end() could do any necessary cleanup.

I looked at how va_end() was implemented in Microsoft Visual Studio and this is how it is defined:

#define va_end(ap) ap = (va_list)0

As you can see, it’s actually a macro function that just sets the ap parameter to 0. So, at least with Microsoft Visual Studio, there’s no real practical effect of calling va_end(), outside of maybe NULLing your list in case you inadvertently try to use it again without calling va_start().

In your example, you’d have to pass list into va_end(), but va_start() should cause the list to start at the beginning of the ellipses again — so yes, nX would be the first element of the ellipses.

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