C++ Programming :: preprocessor seems interfering namespace defines?


	preprocessor seems interfering namespace defines? Hi, all: I have a question regarding to how to solve following problem: I have header called myHeader.h which #define MAX_LEN 100 (legacy code). Now, I like to put most commonly used in myHeader.h into a namespace, e.g., #include <myHeader.h> namespace myNamespace { const int MAX_LEN = 100; MyData data[MAX_NUM]; //MyData defined in myHeader.h }; Unfortunately, I have to include myHeader.h and compiler fails me due to that MAX_LEN is probably replaced with 100 by preprocessor since it complains about syntax error, what is best way to solve this? thx On 5/30/2007 3:20 PM, wenm@yahoo.com wrote: > Hi, all: > I have a question regarding to how to solve following problem: > I have header called myHeader.h which #define MAX_LEN 100 (legacy > code). > Now, I like to put most commonly used in myHeader.h into a namespace, > e.g., > #include <myHeader.h> #ifdef MAX_LEN #undef MAX_LEN #endif > namespace myNamespace > { > const int MAX_LEN = 100; > MyData data[MAX_NUM]; //MyData defined in myHeader.h You certainly meant: MyData data[MAX_LEN]; > }; > Unfortunately, I have to include myHeader.h and compiler fails me due > to that MAX_LEN is probably replaced with 100 by preprocessor since it > complains about syntax error, what is best way to solve this? If you can, ditch the preprocessor usage in 'myHeader.h'. Regards, Stefan -- Stefan Naewe stefan dot naewe at atlas-elektronik dot com Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html wenm@yahoo.com wrote: > Unfortunately, I have to include myHeader.h and compiler fails me due > to that MAX_LEN is probably replaced with 100 by preprocessor since it > complains about syntax error, what is best way to solve this? > thx Use a different name for your macro. -- -- Pete Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The Standard C++ Library Extensions: a Tutorial and Reference." (www.petebecker.com/tr1book) Pete Becker wrote: > wenm@yahoo.com wrote: >> Unfortunately, I have to include myHeader.h and compiler fails me due >> to that MAX_LEN is probably replaced with 100 by preprocessor since it >> complains about syntax error, what is best way to solve this? >> thx > Use a different name for your macro. s/macro/object/. -- -- Pete Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The Standard C++ Library Extensions: a Tutorial and Reference." (www.petebecker.com/tr1book) On 30 Maj, 15:20, "wenm@yahoo.com" <wenm@yahoo.com> wrote: - Hide quoted text - > Hi, all: > I have a question regarding to how to solve following problem: > I have header called myHeader.h which #define MAX_LEN 100 (legacy > code). > Now, I like to put most commonly used in myHeader.h into a namespace, > e.g., > #include <myHeader.h> > namespace myNamespace > { > const int MAX_LEN = 100; > MyData data[MAX_NUM]; //MyData defined in myHeader.h > }; > Unfortunately, I have to include myHeader.h and compiler fails me due > to that MAX_LEN is probably replaced with 100 by preprocessor since it > complains about syntax error, what is best way to solve this? > thx Your problem would never have occured had you followed the good advice to reserve names all in uppercase for macroes. Rename your constant to max_len. /Peter Thanks all for replying to my question. I have other problem which is not caused by our code, instead from Linux/system headers. I have defined a file scope var, e.g., in my.C: #include "my.h" const int MAX_INT = std::numeric_limits<int>::max(); : : When I compile, max is replaced with a macro defined in /usr/include/ LiS/sys/LiS/share.h #define max(a,b) (((a)>(b))?(a):(b)) And compiler complains: `max' is not a member of type ` std::numeric_limits<int>' how am I going to use soemthing like "std::numeric_limits<int>::max();"? My platform is: Linux server 2.4.21-15.ELsmp #1 SMP Thu Apr 22 00:18:24 EDT 2004 i686 i686 i386 GNU/Linux - Hide quoted text - <wenm@yahoo.com> wrote in message ... > I have other problem which is not caused by our code, instead from > Linux/system headers. > I have defined a file scope var, e.g., in my.C: > #include "my.h" > const int MAX_INT = std::numeric_limits<int>::max(); > : > When I compile, max is replaced with a macro defined in /usr/include/ > LiS/sys/LiS/share.h > #define max(a,b) (((a)>(b))?(a):(b)) > And compiler complains: > `max' is not a member of type ` > std::numeric_limits<int>' Did you: #include <limits> #include <limits> #include <iostream> #include <iomanip> int main(){ std::cout <<" 0x"<<std::hex <<std::numeric_limits<int>::max()<<std::endl; return 0; } -- Bob R POVrookie On May 31, 5:38 pm, "BobR" <removeBadB@worldnet.att.net> wrote: - Hide quoted text - > <wenm@yahoo.com> wrote in message ... > > I have other problem which is not caused by our code, instead from > > Linux/system headers. > > I have defined a file scope var, e.g., in my.C: > > #include "my.h" > > const int MAX_INT = std::numeric_limits<int>::max(); > > : > > When I compile, max is replaced with a macro defined in /usr/include/ > > LiS/sys/LiS/share.h > > #define max(a,b) (((a)>(b))?(a):(b)) > > And compiler complains: > > `max' is not a member of type ` > > std::numeric_limits<int>' > Did you: > #include <limits> > #include <limits> > #include <iostream> > #include <iomanip> > int main(){ > std::cout <<" 0x"<<std::hex > <<std::numeric_limits<int>::max()<<std::endl; > return 0; > } > -- > Bob R > POVrookie yes, I did. For a simple test, it compiles/works fine without including share.h. share.h is indirectly included by other legacy code, preprocessor seems failing the includes. wenm@yahoo.com wrote: > yes, I did. For a simple test, it compiles/works fine without > including share.h. share.h is indirectly included by other legacy > code, preprocessor seems failing the includes. Right. the problem is the macro max(), which conflicts with the member function with the same name (the algorithm max has the same problem, but it sounds like you haven't hit that one yet). Under Windows, the solution is to define _NO_MINMAX (or something like that, it's been a while) before including the offending files. If there isn't a mechanism like that for the file that's messing up your code, one approach would be to start every list of include files with: #include "share.h" #undef max That way you'll blow away the macro before it does any damage to headers that aren't prepared for it. On the other hand, it might cause problems for other headers from the same package that assume that the macro definition is still there. If that's the case, one possibility (NOT TESTED) would be: #include "share.h" #undef max #include <algorithm> using std::max; That kills the macro, but puts the C++ algorithm named max in the global namespace, where subsequent headers will see it. I wouldn't do this automatically, only if it's needed to solve actual problems. It may well be that the macro max is only used in the library's source files, so all you need to do is get rid of it. Another approach, if you don't mind doing a little surgery on your compiler's headers, is to find all their uses of max and replace them with (max) (i.e. put parentheses around them). The preprocessor won't treat a name as a function-like macro if it's not followed by a left parenthesis, so it won't mess with those uses of max. You'll have to do the same in your source code if you use max: return (max)(a, b); -- -- Pete Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The Standard C++ Library Extensions: a Tutorial and Reference." (www.petebecker.com/tr1book) On Jun 1, 10:12 am, Pete Becker <p@versatilecoding.com> wrote: - Hide quoted text - > wenm@yahoo.com wrote: > > yes, I did. For a simple test, it compiles/works fine without > > including share.h. share.h is indirectly included by other legacy > > code, preprocessor seems failing the includes. > Right. the problem is the macro max(), which conflicts with the member > function with the same name (the algorithm max has the same problem, but > it sounds like you haven't hit that one yet). > Under Windows, the solution is to define _NO_MINMAX (or something like > that, it's been a while) before including the offending files. If there > isn't a mechanism like that for the file that's messing up your code, > one approach would be to start every list of include files with: > #include "share.h" > #undef max > That way you'll blow away the macro before it does any damage to headers > that aren't prepared for it. On the other hand, it might cause problems > for other headers from the same package that assume that the macro > definition is still there. If that's the case, one possibility (NOT > TESTED) would be: > #include "share.h" > #undef max > #include <algorithm> > using std::max; > That kills the macro, but puts the C++ algorithm named max in the global > namespace, where subsequent headers will see it. I wouldn't do this > automatically, only if it's needed to solve actual problems. It may well > be that the macro max is only used in the library's source files, so all > you need to do is get rid of it. > Another approach, if you don't mind doing a little surgery on your > compiler's headers, is to find all their uses of max and replace them > with (max) (i.e. put parentheses around them). The preprocessor won't > treat a name as a function-like macro if it's not followed by a left > parenthesis, so it won't mess with those uses of max. You'll have to do > the same in your source code if you use max: > return (max)(a, b); > -- > -- Pete > Roundhouse Consulting, Ltd. (www.versatilecoding.com) > Author of "The Standard C++ Library Extensions: a Tutorial and > Reference." (www.petebecker.com/tr1book) Thanks Pete. I have not traced back where share.h is included in our code, but most likely it is include indirectly by other headers. I guess that I may end up using #undef to solve the problem.