C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Underline importance of forbidden names          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Attila Feher Guest Posted: Thu Mar 17, 2005 2:22 am    Post subject: Underline importance of forbidden names Hi All, Could someone please double check, if I remember right, or did I miss something about reserved names? The following names are reserved for the implementation: - any name containing two consecutive underscores - any global namespace level name, starting with an underscore (does this forbid such names in unnamed namespaces as well?) - any name starting with an underscore followed by an uppercase letter - any namespace level name starting with the letters str followed by a lowercase letter Did I miss anything? Is anything I wrote wrong? It is probably worth to mention the "MACRO NAMESPACE" also in this list (although only convention)? -- Attila aka WW [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ray Lischner Guest Posted: Thu Mar 17, 2005 12:39 pm    Post subject: Re: Underline importance of forbidden names On Wednesday 16 March 2005 09:22 pm, Attila Feher wrote: Quote: The following names are reserved for the implementation: ..... - any namespace level name starting with the letters str followed by a lowercase letter My understanding is that these are names are reserved only if <cstdlib> is included. (Of course, one never knows whether <cstdlib> is included if you have included at least one standard header.) Reserved identifiers from the C90 standard are (section 7.13): <cerrno>: macros that begin with E<digit> or E<uppercase>. <cctype>: Functions that start with is<lower> or to<lower>. <clocale>: Macros that start with LC_<upper> <cmath>: all the math functions with a suffix of "f" or "l" <csignal>: Macros that start with SIG<upper> or SIG_<upper> <cstdlib>: Functions that start with str<lower> <cstring>: Functions that start with str<lower>, mem<lower>, or wcs<lower>. -- Ray Lischner, author of C++ in a Nutshell http://www.tempest-sw.com/cpp [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top kanze@gabi-soft.fr Guest Posted: Thu Mar 17, 2005 9:52 pm    Post subject: Re: Underline importance of forbidden names Attila Feher wrote: Quote: Could someone please double check, if I remember right, or did I miss something about reserved names? The following names are reserved for the implementation: - any name containing two consecutive underscores - any global namespace level name, starting with an underscore (does this forbid such names in unnamed namespaces as well?) No. A name in an unnamed namespace is not in global namespace. Quote: - any name starting with an underscore followed by an uppercase letter Quote: - any namespace level name starting with the letters str followed by a lowercase letter Did I miss anything? Is anything I wrote wrong? It is probably worth to mention the "MACRO NAMESPACE" also in this list (although only convention)? I think that your last point is wrong, at least in C++. In C, there is a section concerning future library directions, which reserves a lot of names for future library extensions: -- all names beginning with is or to, followed by a lower case letter, if you include <ctype.h> or <wctype.h>; -- all names beginning with E followed by a digit or an upper case letter, if you include <errno.h>; -- all names beginning with PRI or SCN followed by a lower case letter or an X, if you include <inttypes.h>; -- all names beginning with LC_ followed by an upper case letter if you include <locale.h>; -- all names beginning with SIG or SIG_ followed by an upper case letter, if you include <signal.h>; -- all names beginning with int or uint and ending with _t, and names beginning with INT or UINT and ending with _MAX, _MIN or _C, if you include <stdint.h>; -- all names beginning with str followed by a lower case letter, if you include <stdlib.h> or <string.h>; -- all names beginning with mem followed by a lower case letter, if you include <string.h>; and -- all names beginning with wcs and a lower class letter, if you include <string.h> or <wchar.h>. Plus, of course, anything formally defined in the header. That's a lot, but note that the restrictions are only if you include the specified header. The case of C++ is significantly different. To begin with, unlike C, in C++, one standard header can include any of the others. So the restriction "only if you include the given standard header" cannot apply. On the other hand, except for the <xxx.h> compatibility headers, the C++ standard puts almost everything in std:: (and allows almost no macros). The result is that for the most part, you don't have to worry about any of the above -- the next version of the standard can add pretty much anything it wants to std:: without risk of breaking your code. There are a few issues that the standard doesn't seem to mention. Presumably, for example, the C++ standard will extend the <c...> headers to track fairly closely what the C standard does. This means that in the cases above where the name is required to be a macro, if you include the corresponding <c...> header, you have to avoid the names as well. (Roughly speaking, and without verifying, this would be the names using upper case letters.) Other than this, you have also forgotten all of the keywords and alternate tokens. And of course, that is for the standard. In practice, no compiler I know implements the <c...> includes correctly, so you risk problems if you define anything in the global namespace whose name is the same as that of a standard C function, even if you include the <c...> form of the header; for that matter, there is a decided risk that the implementation of the library uses some of the C functions in global namespace, so if you define a function `extern "C" memcpy', for example, you're looking for trouble (but there is no exhaustive list that I know of, and technically, the standard says you have the right, as long as you don't include <string.h>). Finally, of course, you're probably not using C++ in a vacuum. I know that I almost never write an application of any size which doesn't use some Posix functionality; the situation is doubtlessly the same for people working on Windows platforms. And Posix introduces a lot more reserved symbols, etc. (On my platform, Solaris, there are even a few macros with names beginning with a _, followed by a lower case letter. Which means that using such symbols is bad even in private scopes.) In the end, the rules are 1) complicated, 2) not very clear, and 3) they vary from one platform to the next. Pragmatically, I avoid all symbols beginning with a _ or containing two successive __, avoid all standard and system standard function names that I know, at least at global scope, and hope that the compiler will complain, or at least that the code will core dump immediately, if I accidentally get a collision. Not really a very satisfactory solution, but I don't have anything better. -- James Kanze GABI Software Conseils en informatique orientée objet/ Beratung in objektorientierter Datenverarbeitung 9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34 [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top White Wolf Guest Posted: Thu Mar 17, 2005 9:56 pm    Post subject: Re: Underline importance of forbidden names Ray Lischner wrote: Quote: On Wednesday 16 March 2005 09:22 pm, Attila Feher wrote: The following names are reserved for the implementation: .... - any namespace level name starting with the letters str followed by a lowercase letter My understanding is that these are names are reserved only if <cstdlib is included. (Of course, one never knows whether if you have included at least one standard header.) Well, my point is that I would like to keep it simple; and since the people I will talk to (well, mail to but that is irrelevant) will never write production code without using 3rd party libraries, for them these names are simply not allowed. Since any 3rd party library (linked into the application) might have used any of those headers. In which case the problems will come during linking - which happens at startup, in the worst case. Quote: Reserved identifiers from the C90 standard are (section 7.13): cerrno>: macros that begin with E<digit> or E<uppercase>. cctype>: Functions that start with is<lower> or to<lower>. clocale>: Macros that start with LC_<upper cmath>: all the math functions with a suffix of "f" or "l" csignal>: Macros that start with SIG<upper> or SIG_<upper cstdlib>: Functions that start with str<lower cstring>: Functions that start with str<lower>, mem<lower>, or wcs<lower>. Thank you Ray, this is just excellent! I did not know most of the above. Shame on me, but I am clever enough to ask. :-) I guess the list above says, that those are in the std/global namespace. I can have my strcpy in the buffer_overflow namespace, and still be compliant right? I - of course - meant the function name issues, not the MACROs. :-) IIRC C++ does not allow functions to be macros, so they cannot "invade" a namespace or (class) scope right? -- WW aka Attila ::: If you always do what you've always done, you'll always get what you've always gotten. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top kanze@gabi-soft.fr Guest Posted: Sat Mar 19, 2005 12:14 am    Post subject: Re: Underline importance of forbidden names Ray Lischner wrote: Quote: On Wednesday 16 March 2005 09:22 pm, Attila Feher wrote: The following names are reserved for the implementation: .... - any namespace level name starting with the letters str followed by a lowercase letter My understanding is that these are names are reserved only if cstdlib> is included. <cstdlib>, <stdlib.h>, <string> or <string.h>. Quote: (Of course, one never knows whether <cstdlib> is included if you have included at least one standard header.) No. Or at least I don't think so. As I understand it, the C rules rule for the C header files, including the <cxxx> variants. Of course, in practice, you don't include just standard headers, and you can't generally be too sure about what the other headers you include might include. -- James Kanze GABI Software Conseils en informatique orientée objet/ Beratung in objektorientierter Datenverarbeitung 9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34 [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ben Hutchings Guest Posted: Tue Mar 22, 2005 9:06 am    Post subject: Re: Underline importance of forbidden names White Wolf wrote: Quote: Ray Lischner wrote: snip Reserved identifiers from the C90 standard are (section 7.13): cerrno>: macros that begin with E<digit> or E<uppercase>. cctype>: Functions that start with is<lower> or to<lower>. clocale>: Macros that start with LC_<upper cmath>: all the math functions with a suffix of "f" or "l" csignal>: Macros that start with SIG<upper> or SIG_<upper cstdlib>: Functions that start with str<lower cstring>: Functions that start with str<lower>, mem<lower>, or wcs<lower>. Thank you Ray, this is just excellent! I did not know most of the above. Shame on me, but I am clever enough to ask. :-) I guess the list above says, that those are in the std/global namespace. I can have my strcpy in the buffer_overflow namespace, and still be compliant right? I - of course - meant the function name issues, not the MACROs. :-) IIRC C++ does not allow functions to be macros, so they cannot "invade" a namespace or (class) scope right? Correct. The functions from the C library that the C standard allows to be macros as well are supposed to be defined only as functions in the C++ library. I don't know whether there are any current implementations that violate this; I don't remember running into myself. Of course there are a few names that are defined as macros in both versions of the library, notably "assert". -- Ben Hutchings Having problems with C++ templates? Your questions may be answered by <http://womble.decadentplace.org.uk/c++/template-faq.html>. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ Language (Moderated) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.