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Linker Error Anonymous Namespace

static functions0Undefined Reference to namespaces in C++1C++ undefined references to functions in namespace0Namespaces & Undefined References1Arduino Linker Errors When Using a Spesific Namespace Name0Namespace function linker error when used in multiple That class is nested inside an anonymous namespace. This particular source file also happens to contain "main". more hot questions question feed lang-cpp about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation http://softacoustik.com/linker-error/linker-error-in-c.php

Make them static. This way, we reduce dependency on the file containing the definition. Just a little change and we're talking physical education Is a food chain without plants plausible? Reply Nemo Publius (@NemoPublius) says: September 3, 2014 at 1:53 am "If it’s static, the compiler/linker will probably not deduplicate it across translation units." Not "probably"; definitely.

However, I must admit than the fact that whith inline you are required to ensure that each definition is identical is a nice to have even though I think this does Example: //hpp #ifndef __BAR_HPP_ #define __BAR_HPP_ namespace foo { namespace { struct Bar { void func(); }; } } #endif //cpp using foo; void Bar::func() { //... } c++ namespaces share|improve more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed

It has been recently described by John Lakos in this presentation. The definition of such a translation unit is very simple: Any file, fed to the compiler, after it has been pre-processed. This way, the compiler can identify the function by its prototype, but we can remove the dependency of file.hpp on the file containing the definition of Class, say class.hpp: // file.hpp When function2 is called, file2.cpp’s copy of variable is set to 123.

For objects, this means that the compiler will literally allocate an entirely new, unique copy for each translation unit, which can obviously incur high memory costs. If you don’t declare them static, they will implicitly have external linkage and the first foo’s definition will collide with the second foos definition and cause a linker error due to C++ delete a pointer (free memory) Name spelling on publications How to unlink (remove) the special hardlink "." created for a folder? The contents of the nameless namespace are local to one sourcefile, so whoever's coding that file is free to choose whatever identifiers they like for names within that namespace, and so

Inlining is about multiple definition, and is either implicit (template, class definition) or explicit (keyword inline). And it's quite a useful warning otherwise. Please enable JavaScript to view the comments powered by Disqus. This is the only disadvantage of `static`, compared to `inline`, that I can think of.

Its usage here is entirely separate from its usage in classes or functions (or, generally, any block). https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26984 Above it was mentioned that const global variables have internal linkage by default, and non-const global variables have external linkage by default. Here's how it looks at the moment: namespace { int EatGrass() { return 5; } } int main() { EatGrass(); } Later, we decide that we need something from the library, Sieve of Eratosthenes, Step by Step Kio estas la diferenco inter scivola kaj scivolema?

For the "static" version, each instance of the function (because there are several) must have its own address. http://softacoustik.com/linker-error/linker-error-in-c-tv-lib.php What to do with my out of control pre teen daughter Referee did not fully understand accepted paper Who is the highest-grossing debut director? 2002 research: speed of light slowing down? Added: trunk/gcc/testsuite/g++.dg/ext/visibility/anon2.C trunk/gcc/testsuite/g++.dg/ext/visibility/class1.C trunk/gcc/testsuite/g++.dg/ext/visibility/prop1.C trunk/gcc/testsuite/g++.dg/ext/visibility/redecl1.C trunk/gcc/testsuite/g++.dg/ext/visibility/template1.C trunk/gcc/testsuite/g++.dg/ext/visibility/template2.C trunk/gcc/testsuite/g++.dg/ext/visibility/template3.C trunk/gcc/testsuite/g++.dg/ext/visibility/template4.C trunk/gcc/testsuite/g++.dg/ext/visibility/typeinfo1.C trunk/gcc/testsuite/g++.dg/ext/visibility/warn1.C trunk/gcc/testsuite/g++.dg/ext/visibility/warn2.C trunk/gcc/testsuite/g++.dg/ext/visibility/warn3.C trunk/gcc/testsuite/g++.dg/ext/visibility/warn4.C Modified: trunk/gcc/ChangeLog trunk/gcc/attribs.c trunk/gcc/c-common.c trunk/gcc/c-decl.c trunk/gcc/cp/ChangeLog trunk/gcc/cp/class.c trunk/gcc/cp/cp-tree.h trunk/gcc/cp/decl.c trunk/gcc/cp/decl2.c trunk/gcc/cp/name-lookup.c trunk/gcc/cp/parser.c trunk/gcc/cp/pt.c trunk/gcc/cp/rtti.c trunk/gcc/cp/semantics.c trunk/gcc/cp/tree.c trunk/gcc/doc/extend.texi Given these files: header.hpp: #ifndef HEADER_HPP #define HEADER_HPP #define VALUE 5 #ifndef VALUE struct Foo { private: int ryan

If you were to define such a symbol on the spot, along with declaring it, or to place its definition in the same file you declare it, you run the risk I have found inline functions useful, and its usefulness has nothing to do with inlining. I realized that I needlessly created a function template where a normal function would suffice. http://softacoustik.com/linker-error/linker-error-c0-asm.php Adding another CPP file would require of me integrating it with version control system, adding it to makefile; I decided it was too big an effort for that moment.

I will just drop the namespace. –clambake Apr 9 '14 at 8:13 You can think of an anonymous namespace as a replacement for the static linkage specifier (as opposed With `inline` you are required to ensure that each definition is identical, as already stated in this blog. A namespace function?

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Not only should they be identical token by token, but the same name of a variable must refer to the very same object in each source file. I observed the following problem: [ GNU ld cross compiling to 32 bit ] fine: linker error with reasonable error message [ GNU gold cross compiling to 32 bit ] not Compiler is not allowed to complain about multiple definitions. Because it’s the linker’s lucky day, it will even find two!

Reply germinolegrand says: July 14, 2014 at 2:40 pm Nice subject. Feedback welcome! Why is JK Rowling considered 'bad at math'? http://softacoustik.com/linker-error/linker-error.php Not quite.

So there doesn't seem to be much of a need for a mechanism to get around this deficiency. I heard about this useful technique from Sean Parent in this talk. But why? That should be easy, because it is only used in one file.

Related Posts Disassembling Python Bytecode Insight into Python bytecode disassembly with the dis module. Bit Manipulation Tips and concepts associated with bit-manipulation and a few sample problems. but alas, the following give us a linker error: #include namespace { int EatGrass() { return 5; } int main() { EatGrass(); /* Intends to call internal func */ } True, I could have changed it into declaration, add a CPP file and put the definition in there, but while doing refactoring in a big project and under risking of leaving

By doing so, we don’t have to include the full definition of a symbol (usually a header file) when it is not explicitly necessary. When I do so I get an undefined reference error. What should I use? Related This entry was posted in programming and tagged C++03.

Or put it in an anonymous namespace in the Bar implementation file. –nbt May 3 '11 at 8:28 Oddly, this seems to work for me... What's needed is: void foo::Bar::func() { /*impl...*/ } But what do you put in place of foo:: to refer to the name of an anonymous namespace? Or, if you don't want to make the compiler create the code again and again in all files, you of course need to have the implementation just once in one .cpp Why won't a series converge if the limit of the sequence is 0?

asked 4 years ago viewed 1143 times active 4 years ago Get the weekly newsletter! I want to understand WHY I should do what you recommend. –user1697999 Apr 23 '14 at 0:25 Compiler is invoked several times, most of the time for each .cpp With modern compilers increasingly making their own decisions about inlining calls and not necessarily paying much attention to the user's request this may not be as necessary these days but you If you define it in the header as a non-inline non-static function and include it in more than one source file of a program, the linker will be presented with copies

Here is some example code that reproduces the situation: main.cpp: #include "notmain.h" #include "theclass.h" A *ourA=NULL; int main() { theA = new A(); theA->dostuff(1024); sunshine sun; sun.Init(); } notmain.cpp: #include "notmain.h" Browse other questions tagged c++ static namespaces or ask your own question. Target: i686-pc-linux-gnu Configured with: /lab/rjpeters/build/gcc-4.2-20060401/configure --enable-languages=c,c++ --prefix=/lab/rjpeters/local/gcc-4.2-20060401 --enable-shared --enable-threads=posix --with-system-zlib --enable-__cxa_atexit Thread model: posix gcc version 4.2.0 20060401 (experimental) I get a linker error when I try to compile and link If there were an external linkage function by the same name residing in a different translation unit, then the current translation unit was simply oblivious to it and had no way