Windows error LNK1179

I compiled an exe on windows VS 2005, a c++ program that link to other libs of mine. It compiled and suddenly it doesn't with an error of LNK1170 COMDAT "

I can't understand what happened and开发者_StackOverflow中文版 how to solve the problem.

Thanks

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There is many issues concerning this bug including:

• using of unnamed stuff (struct, class, namespace)
• instantiation of template parameter
• incremental linking
• ...

I experienced the bug in situation like this:

template < class InputIterator >
Id findOrInsertSomething( const std::string & name, InputIterator begin, InputIterator end )
{
    Id out;
    {
        static std::string sql( calculateQueryA() );
        if (findSomething( sql, name, out ))
            return out;
    }

    static std::string sql( calculateQueryB() );
    out = insertSomehing( sql, name, begin, end );
    return out;
}

When used in code, link error LNK1179 occurred. Problem is simple. Even without /H switch, maximum length of names can be 2047 characters. When using template stuff, usually very long names are created. In the example there are 2 static variables with the same name. They will be named like:

sql?something-like-function-signature?something-like-block-signature

what can be easily longer then 2047 characters. Because something-like-block-signature is at the end, it will be behind 2047 boundary, making effectively both sql variables the same for the linker.

Solution is easy:

• using different names
• hide optimization in function (will not be calculated for each version of the template)

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This is copied from http://msdn.microsoft.com/en-us/library/aa234469(VS.60).aspx

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Linker Tools Error LNK1179

Visual Studio 6.0

invalid or corrupt file: duplicate comdat comdat

An object module contained two or more COMDATs with the same name.

One possible cause is if you use the /H option with /Gy. The /H option limits the length of external names, and the /Gy option packages functions in COMDATs.

For example, if you compile the following with /Gy and /H8, you will get error LNK1179 since the object module will contain two COMDATs of the same name (function1 and function2 are unique at nine characters):

void function1(void);
void function2(void);

void main(void) {
    function1();
    function2();
}

void function1(void) {}
void function2(void) {}

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Anyway, check the official documentation about it:

http://msdn.microsoft.com/en-us/library/cddbs9aw%28VS.80%29.aspx

http://msdn.microsoft.com/en-us/library/aa234469%28VS.60%29.aspx

And if you check codeguru, a guy found another way to solve a problem similar to yours:

Project->Settings->C++ tab, Debug cathegory: Inline function expansion: change from 'None' to 'Only _inline'.

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I started again the IDE and also reboot the machine and it didn't help. I managed to solve it after I clean and comiple again (not recompile option) 2 libs of mine. I don't understand why it helped but it succeeded to lnik the project.

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Experienced this problem while making a bind to a member function:

std::function<void(Appender<Contact>&)> f = std::bind(&Manager::AppendContacts, this, std::placeholders::_1);

And then passing it somewhere:

gBuf.append(f);

The error was:

LNK1179: invalid or corrupt file: duplicate COMDAT (...)

The member function seems to have the exact same signature as f (or is perhaps exceeding the max limit the linker checks)

If I instead write it inline, without the intermediate f, there is no error.

gBuf.append(std::bind(&Manager::AppendContacts, this, std::placeholders::_1));

I don't pretend to understand what is happening here, but perhaps I can save someone a couple of hours figuring this out like I had to...