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Linker Error Anonymous Namespace

Jul 1 '06 #4 This discussion thread is closed Start new discussion Replies have been disabled for this discussion. It is less obvious that this rule also applies to non-member functions defined inside class: class Span { double begin_; double end_; friend bool operator==(Span const& a, Span const& b) { PR c++/26905 PR c++/21675 PR c++/17470 * parser.c (cp_parser_explicit_instantiation): Pass the attributes to grokdeclarator. (cp_parser_type_specifier): Allow 'enum __attribute ((...)) E'. (cp_parser_enum_specifier): Likewise. (cp_parser_elaborated_type_specifier): Apply attributes if this declares only the class. more hot questions question feed default about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation weblink

Template functions have to be defined in every translation unit that instantiates them (which usually means putting them in a header file) but they are not implicitly inline. Usage A common use case for declaring variables explicitly extern are global variables. More specifically, this is when you get a duplicate symbol error, which is the one you’ll get most often along with an undefined symbol error (if we had only ever declared, You may still want to explicitly declare a template function inline (indicate that inline substitution of the function body at the point of call is to be preferred to the usual http://stackoverflow.com/questions/5866856/undefined-reference-linker-error-when-implementing-function-declared-in-anonymou

Compiler is not allowed to complain about multiple definitions. For the "inline" version, the function (because there is only one) must only have one address. It's quick & easy. One example, which I found at http://stackoverflow.com/questions/4422507/superiority-of-unnamed-namespace-over-static, is this: 1
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namespace { class sample_class { /* class body */ }; } This cannot be achieved by using the static keyword.

You could give the definition an identifier, e.g. #define specificMath specificMath or just don't use the same identifier for both the include guard and namespace. #ifndef SPECIFIC_MATH_H #define SPECIFIC_MATH_H namespace specificMath The Dice Star Strikes Back Kio estas la diferenco inter scivola kaj scivolema? Related 327Unnamed/anonymous namespaces vs. static functions1299Why is “using namespace std” considered bad practice?22Hiding private constants in an inline namespace header1Undefined reference linker error when implementing function declared in anonymous namespace0Undefined Reference to namespaces in C++3Including

It is, in essence, just a way to declare many symbols as static. Nice post. Also, some compilers have a warning for static functions that are not used in a TU. it will be as if you redefined each such symbol in every translation unit.

public: operator Span() const; // no operator== }; Span s; Xspan x; s == x; // OK: s.operator==(x.operator Span()); x == s; // ERROR: no Xspan::operator== So, there is a motivation Not the answer you're looking for? So there doesn't seem to be much of a need for a mechanism to get around this deficiency. 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

This will render an ill-formed program, but compilers are not required to diagnose this. If you write a class definition in a .cpp file, there is (I believe) no way to access it from another .cpp file, regardless of whether it is placed in an How to decipher Powershell syntax for text formatting? It does not make sense to compile the inner workings of all functions again and again, so you leave just the declaration in the header file and then provide its implementation

Comment 3 Andrew Pinski 2006-04-02 16:06:16 UTC Woops wrong person, sorry Nathan. have a peek at these guys Search for: SubscribeRSS - PostsRSS - Comments Recent Posts Concepts Lite vsenable_if Is constructible? 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 Rate this:Share this:LinkedInLike this:Like Loading...

I have 2 classes defined in an anonymous namespace because they are included throughout the whole project. Otherwise you could define them in a separate source file and just declare them in the header file. Can anybody show me a piece of code that will not work without unnamed namespaces and which cannot be solved equally well using "static"? check over here The definition of such a translation unit is very simple: Any file, fed to the compiler, after it has been pre-processed.

And it's quite a useful warning otherwise. What is the 'dot space filename' command doing in bash? While it doesn't make much difference in this case it could for large functions, is there some way around that? –user1697999 Apr 23 '14 at 0:02 Sure, updated the

So what benefit does the unnamed namespace actually give? -- Claus Mar 23, 2011 at 9:10am UTC Bazzy (6281) If a definition is not inside an unnamed namespace the linker will

Naturally, this violates the One-Definition-Rule, so this causes a linker error. Comment 2 Cary Coutant 2016-03-27 23:20:19 UTC Committed patch to diagnose the GOTOFF reference to undefined symbol on i386. Related Posts Disassembling Python Bytecode Insight into Python bytecode disassembly with the dis module. Similar topics question about anonymous namespace...

Browse other questions tagged c++ static namespaces or ask your own question. Accessing anonymous namespace P: n/a Frederick Gotham Back in the day, if you wanted a function to be self-contained within a translation unit, you defined the function as "static". Bookmark the permalink. ← Clever overloading Inadvertent conversions → 13 Responses to Inline functions mgaunard says: July 14, 2014 at 1:42 pm In short: both template and inline symbols are weak this content The main advantage of this is that when the file containing the definition changes, the file where we forward declared that symbol does not need to be re-compiled (and therefore, also

Imagine this: We have a load of header files pertaining to a particular library.