C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  can't get div(int, int) out of global namespace Goto page 1, 2  Next          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message nick@byu.edu Guest Posted: Sun Jun 29, 2003 11:29 am    Post subject: can't get div(int, int) out of global namespace I'm writing my own function int div(int, int). Including any of: <algorithm> <cstdlib> <stdlib> all cause struct div_t div(int, int) to be put into the _global_ namespace. (My understanding is that those should be pulled in by <math.h> or <cmath>, and if by <cmath> then into std::.) Even attempting to #include any of the above inside a namespace std { } block doesn't solve it. I don't care if struct div_t div(int, int) is in std:: --that would be great. I just want to get it out of the global namespace so I can use my own div() w/o having to put it in it's own namespace, and then consequently have to disambiguate it everywhere. Is there a way to do this? (gnu gcc 2.95.3, glibc 2.2.4 if it matters) Nick [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Sebastian Kapfer Guest Posted: Sun Jun 29, 2003 9:15 pm    Post subject: Re: can't get div(int, int) out of global namespace On Sun, 29 Jun 2003 07:29:58 -0400, nic wrote: Quote: Is there a way to do this? (gnu gcc 2.95.3, glibc 2.2.4 if it matters) gcc 2.9x has broken namespaces. std::div will always be ::div using that compiler. Updating to 3.x helps (3.2+ is to be preferred, less bugs). You can still overload the function though, if it takes arguments different from std::div. And even if it takes the same arguments, it *might* work. The linker should prefer functions from .o files to those in .a files. You'll have to declare your function extern "C" possibly. This is pretty shaky terrain... do you really have to call the function "div"? -- Best Regards, | Hi! I'm a .signature virus. Copy me into Sebastian | your ~/.signature to help me spread! [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Early Ehlinger Guest Posted: Sun Jun 29, 2003 10:16 pm    Post subject: Re: can't get div(int, int) out of global namespace <nick (AT) byu (DOT) edu> wrote: Quote: Is there a way to do this? (gnu gcc 2.95.3, glibc 2.2.4 if it matters) It does :) gcc 2.95.x didn't really have its library in std::, IIRC. Instead, everything was in namespace "::" and if you referenced std:: you would get ::. Best course of action? Upgrade to 3.x. -- -- Early Ehlinger CEO, ResPower Inc - Toll-Free : 866-737-7697 -- www.respower.com -- 500+ GHz Supercomputer Starting At USD$0.50/GHz*Hour [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ulrich Eckhardt Guest Posted: Sun Jun 29, 2003 10:19 pm    Post subject: Re: can't get div(int, int) out of global namespace [email]nick (AT) byu (DOT) edu[/email] wrote: Quote: I don't care if struct div_t div(int, int) is in std:: --that would be great. I just want to get it out of the global namespace so I can use my own div() w/o having to put it in it's own namespace, and then consequently have to disambiguate it everywhere. Is there a way to do this? (gnu gcc 2.95.3, glibc 2.2.4 if it matters) First thing with such problems is to check the bug-database of the compiler. There you will quickly find that the version is ancient and that corrections to the (non-standard) stdlib are not done in order not to break any old software. IOW: upgrade your compiler. Second thing is that you hopefully don't want to pollute the global namespace yourself with such a universal name, no ? hth Ulrich Eckhardt -- Questions ? see C++-FAQ Lite: http://parashift.com/c++-faq-lite/ first ! [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Siemel Naran Guest Posted: Sun Jun 29, 2003 10:21 pm    Post subject: Re: can't get div(int, int) out of global namespace <nick (AT) byu (DOT) edu> wrote Quote: I'm writing my own function int div(int, int). Including any of: algorithm cstdlib stdlib all cause struct div_t div(int, int) to be put into the _global_ namespace. (My understanding is that those should be pulled in by math.h> or <cmath>, and if by <cmath> then into std::.) Even attempting to #include any of the above inside a namespace std { } block doesn't solve it. I don't care if struct div_t div(int, int) is in std:: --that would be great. I just want to get it out of the global namespace so I can use my own div() w/o having to put it in it's own namespace, and then consequently have to disambiguate it everywhere. Can you put your div(int,int) into its own namespace? Though it seems your system headers are faulty. In stdlib.h there is a function div(int, int) in the global namespace. But in cstdlib this function is in the standard namespace. If you include cstdlib, and header files like algorithm include only cstdlib, then it should work. My guess is that your system headers are including stdlib.h somewhere. I prove this by writing this program int div(int, int) { // line 2 return 0; } void action() { div(3,2); } #include <algorithm> // line 11 #include <cstdlib> int main() { action(); } In file included from /usr/lib/gcc-lib/i686-pc-cygwin/2.95.2-6/../../../../inclu de/g++-3/stl_algobase.h:50, from /usr/lib/gcc-lib/i686-pc-cygwin/2.95.2-6/../../../../inclu de/g++-3/algorithm:30, from h.cc:11: /usr/include/stdlib.h:61: new declaration `struct div_t div(int, int)' h.cc:2: ambiguates old declaration `int div(int, int)' Line 50 of stl_algobase.h is #include <stdlib.h> On Borland VC6 I find the same thing, but only if I include <vcl.h>. This is the file that defines __InitVCL and __ExitVCL, which you need in order to create the executable, and are specific to Borland. Doubtless, the header <vcl.h> is faulty -- they must be including stdlib.h rather than cstdlib. Solution here is to move the #include <vcl.h> till just before int main(). -- +++++++++++ Siemel Naran [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Hyman Rosen Guest Posted: Sun Jun 29, 2003 10:22 pm    Post subject: Re: can't get div(int, int) out of global namespace Francis Glassborow wrote: Quote: But exactly why are you so determined to use the name 'div' at global level? What is wrong with 'mydiv' or 'Div' or 'divx' etc. I'll bet he's working on the 2003 ICFP contest :-) [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Jack Klein Guest Posted: Sun Jun 29, 2003 10:22 pm    Post subject: Re: can't get div(int, int) out of global namespace On 29 Jun 2003 07:29:58 -0400, [email]nick (AT) byu (DOT) edu[/email] wrote in comp.lang.c++.moderated: Quote: I'm writing my own function int div(int, int). Including any of: algorithm cstdlib stdlib all cause struct div_t div(int, int) to be put into the _global_ namespace. (My understanding is that those should be pulled in by math.h> or <cmath>, and if by <cmath> then into std::.) Even attempting to #include any of the above inside a namespace std { } block doesn't solve it. I don't care if struct div_t div(int, int) is in std:: --that would be great. I just want to get it out of the global namespace so I can use my own div() w/o having to put it in it's own namespace, and then consequently have to disambiguate it everywhere. Is there a way to do this? (gnu gcc 2.95.3, glibc 2.2.4 if it matters) Nick Gcc 2.95 is quite old, and does not conform to standard C++ namespace usage properly. You might have better luck with a current version (3.3.something, I think). But, as Francis pointed out, why can't you just name your function something else? -- Jack Klein Home: http://JK-Technology.Com FAQs for comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html comp.lang.c++ http://www.parashift.com/c++-faq-lite/ alt.comp.lang.learn.c-c++ ftp://snurse-l.org/pub/acllc-c++/faq [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Gabriel Dos Reis Guest Posted: Mon Jun 30, 2003 4:47 am    Post subject: Re: can't get div(int, int) out of global namespace Sebastian Kapfer <sebastian_kapfer (AT) web (DOT) de> writes: Quote: On Sun, 29 Jun 2003 07:29:58 -0400, nic wrote: Is there a way to do this? (gnu gcc 2.95.3, glibc 2.2.4 if it matters) gcc 2.9x has broken namespaces. std::div will always be ::div using that compiler. Updating to 3.x helps (3.2+ is to be preferred, less bugs). You can still overload the function though, if it takes arguments different from std::div. And even if it takes the same arguments, it *might* work. Please notice that it is unspecified whether funtions from the "C" library have C or C++ linkage. Therefore, insisting on defining ones own function named div with the same signature as the standard one is highly unportable and asking for trouble. -- Gabriel Dos Reis, [email]gdr (AT) integrable-solutions (DOT) net[/email] [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Gabriel Dos Reis Guest Posted: Mon Jun 30, 2003 4:47 am    Post subject: Re: can't get div(int, int) out of global namespace "Early Ehlinger" <early (AT) respower (DOT) com> writes: Quote: Best course of action? Upgrade to 3.x. Does that really makes the core issue go away? -- Gabriel Dos Reis, [email]gdr (AT) integrable-solutions (DOT) net[/email] [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Gabriel Dos Reis Guest Posted: Mon Jun 30, 2003 4:48 am    Post subject: Re: can't get div(int, int) out of global namespace "Siemel Naran" <SiemelNaran (AT) KILL (DOT) att.net> writes: Quote: nick (AT) byu (DOT) edu> wrote I'm writing my own function int div(int, int). Including any of: algorithm cstdlib stdlib all cause struct div_t div(int, int) to be put into the _global_ namespace. (My understanding is that those should be pulled in by math.h> or <cmath>, and if by <cmath> then into std::.) Even attempting to #include any of the above inside a namespace std { } block doesn't solve it. I don't care if struct div_t div(int, int) is in std:: --that would be great. I just want to get it out of the global namespace so I can use my own div() w/o having to put it in it's own namespace, and then consequently have to disambiguate it everywhere. Can you put your div(int,int) into its own namespace? That is no better. In case the standard div has a C linkage. -- Gabriel Dos Reis, [email]gdr (AT) integrable-solutions (DOT) net[/email] [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top llewelly Guest Posted: Mon Jun 30, 2003 4:48 am    Post subject: Re: can't get div(int, int) out of global namespace [email]nick (AT) byu (DOT) edu[/email] writes: Quote: I'm writing my own function int div(int, int). Including any of: algorithm cstdlib stdlib all cause struct div_t div(int, int) to be put into the _global_ namespace. (My understanding is that those should be pulled in by math.h> or <cmath>, and if by <cmath> then into std::.) Even attempting to #include any of the above inside a namespace std { } block doesn't solve it. I don't care if struct div_t div(int, int) is in std:: --that would be great. I just want to get it out of the global namespace so I can use my own div() w/o having to put it in it's own namespace, and then consequently have to disambiguate it everywhere. Is there a way to do this? (gnu gcc 2.95.3, glibc 2.2.4 if it matters) [snip] Upgrade to gcc 3.x [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ulrich Eckhardt Guest Posted: Mon Jun 30, 2003 9:49 am    Post subject: Re: can't get div(int, int) out of global namespace Gabriel Dos Reis wrote: Quote: "Siemel Naran" <SiemelNaran (AT) KILL (DOT) att.net> writes: | <nick (AT) byu (DOT) edu> wrote | Can you put your div(int,int) into its own namespace? That is no better. In case the standard div has a C linkage. Did you really mean what it seems you meant ? Is this bad in any way ? <file cstdlib> extern "C" int(div(int,int); <file foo.cpp> namespace phoob4r { int div(int,int); } Ulrich Eckhardt -- Questions ? see C++-FAQ Lite: http://parashift.com/c++-faq-lite/ first ! [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Gabriel Dos Reis Guest Posted: Mon Jun 30, 2003 4:05 pm    Post subject: Re: can't get div(int, int) out of global namespace Ulrich Eckhardt <doomster (AT) knuut (DOT) de> writes: Quote: Gabriel Dos Reis wrote: "Siemel Naran" <SiemelNaran (AT) KILL (DOT) att.net> writes: | <nick (AT) byu (DOT) edu> wrote | Can you put your div(int,int) into its own namespace? That is no better. In case the standard div has a C linkage. Did you really mean what it seems you meant ? Is this bad in any way ? file cstdlib extern "C" int(div(int,int); file foo.cpp namespace phoob4r { int div(int,int); } ::div and phoob4r::div are the same. See 7.5/6 and 7.5/5. -- Gabriel Dos Reis, [email]gdr (AT) integrable-solutions (DOT) net[/email] [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Gabriel Dos Reis Guest Posted: Mon Jun 30, 2003 4:45 pm    Post subject: Re: can't get div(int, int) out of global namespace Daniel Spangenberg <dsp (AT) bdal (DOT) de> writes: Quote: Hello, Gabriel! Gabriel Dos Reis schrieb: [snip9 Please notice that it is unspecified whether funtions from the "C" library have C or C++ linkage. Therefore, insisting on defining ones own function named div with the same signature as the standard one is highly unportable and asking for trouble. You are abolutely right. But I think, he could use a SFINAE variant, which I proposed for compile time tests of the available ::std::abs and ::abs signatures as well as linkage types. The implementation is mainly based on ideas of Rani Sharoni. How can SFINAE solve that problem in a reliable way? Suppose the program P is composed of two translation units TU1 and TU2. Further assume that TU1 #includes a standard header that brings a declaration of ::div with a C linkage. Also assume that in TU2 he defines "successfully" his own ::div with the same signature (but now with a C++ linkage), then 7.5/5 applies and that is an ODR violation. Quote: If you are interested, have a Google for "C++98 compliant abs/fabs signature tester? (LONG) " or combine the Words "Spangenberg Unique abs". Thanks, I'll check. -- Gabriel Dos Reis, [email]gdr (AT) integrable-solutions (DOT) net[/email] [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Sebastian Kapfer Guest Posted: Mon Jun 30, 2003 6:36 pm    Post subject: Re: can't get div(int, int) out of global namespace On Mon, 30 Jun 2003 00:48:09 -0400, Gabriel Dos Reis wrote: Quote: | > great. I just want to get it out of the global namespace so I can | > use my own div() w/o having to put it in it's own namespace, and then | > consequently have to disambiguate it everywhere. | | Can you put your div(int,int) into its own namespace? That is no better. In case the standard div has a C linkage. If user::div has C++ linkage (or no linkage at all, e.g. inline/static), I can see no problem. -- Best Regards, | Hi! I'm a .signature virus. Copy me into Sebastian | your ~/.signature to help me spread! [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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