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PONamespaces in C Headers
 

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    <p>We have a code base where there are .cpp and .h, it is set up to be build with gcc </p> <p>my understanding is that gcc will choose the appropriate compiler for the appropriate files so I believe (and testing has made me almost 100% sure) that our .h files are compiled as c and our .cpp files are compiled as C++.</p> <p>I once tried to change to g++ and got a whole spate of errors, the same is true when I try and use .hpp. </p> <p>So to get around the issue, most of the time I just use extern C++ when I need to (e.g. when including map) </p> <p>However I can't seem to get it right for namespaces. I assume the compiler is complaining about my namespace because it is being compiled as .h? is this correct. My current code looks like (after trying it without the extern):</p> <p>in foo.h</p> <pre><code> extern "C++" { namespace Caching_Logic { class foo { .... } } } </code></pre> <p>in bar.h</p> <pre><code> extern "C++" { using namespace Caching_Logic; //completely defeats the point of namespaces } class bar { .... foo m_foo; ... } </code></pre> <p>Both files are included by .cpp files</p> <p>and the error when compiling is:</p> <p>filethatusesbar.cpp: error: ‘class bar’ has no member named ‘m_foo’</p> <p>bar.h : error: ‘Caching_Logic’ is not a namespace-name</p> <p>bar.h : error: expected namespace-name before ‘;’ token</p> <p>I am considering just giving up on the namespace entirely but I really like to scope my code for this!</p> <p>-----UPDATE------</p> <p>After reading <a href="http://www.network-theory.co.uk/docs/gccintro/gccintro_54.html" rel="nofollow">http://www.network-theory.co.uk/docs/gccintro/gccintro_54.html</a></p> <p>I have a slightly better understanding of what gcc does. originally I read somewhere that gcc compiles in C++ when necessary and in C when it comes across a .c</p> <p>This is true but it would seem that there is then a problem with the linker. As this is compiled as a library it makes sense that i have not seen an issue before. I am guessing that this is related to my scope issue, external linkage?</p>
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    1. COYou don't need (and in most cases, shouldn't even have) `extern "C++"`. That's the default. And even if your headers were compiled as C (which they're not), AFAIK a standard C compiler wouldn't even know what to do with `extern "C++"`, let alone any mention of classes and namespaces. That's all C++ syntax.
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      1. UScHao
    2. COC knows nothing about namespaces. Why do you think it would compile?
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      1. USCaptain Obvlious
    3. COI have found extern "C++" to work in the past, as mentioned in my post if i #include map in the header file, it does not like it, however if I wrap it in
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      1. USchrispepper1989
 

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