unresolved external symbol link error with R2009b and VC++2008 express sp1

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Sangkyun Kim 2011-7-19

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Hello

I tried to start use c-mex function of Matlab recently. I use R2009b, and VC++2008 express sp1 for the c compliler. As I use just simple equations on c file, such as twotimes function, there is no problem.

However, when I use some external library for the simple socket programming, I got below link error messages.

--------------------------------------------

 error LNK2019: unresolved external symbol __imp_listen referenced in function mdlInitializeConditions

---------------------------------------------

I read many useful helps in this site, and tried many things, but this error is not disappeared. It looks like I have to select library path for the Matlab. But I dont have any clues.

If someone answer how to solve this problem, it will be great help.

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Answer 1

Friedrich 2011-7-19

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Hi,

without some more details it hard to tell whats wrong. Maybe the Microsoft doc can help:

http://msdn.microsoft.com/en-us/library/799kze2z%28v=vs.80%29.aspx

You have to make sure that the compiler/linker can see the needed header and libraries. For this you have the -I and -L options in the mex command.

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Sangkyun Kim 2011-7-20

Thank you Friedrich

I read the document of microsoft.

However, it looks like the library is not included by linker even now.

My purpose is to make a simple socket program using c-mex.

As you know, socket programming of Window needs the library of WS32_2.lib

For my case, the library is under "C:\Program Files\Microsoft SDKs\Windows\v7.0\Lib\x64"

I tried to set this folder as library folder using -L option following your advice. but I got a message as like below.

-----------------

>> mex -v sfun.c -LC:\Program Files\Microsoft SDKs\Windows\v7.0\Lib\x64 -l WS2_32.Lib

C:\PROGRA~1\MATLAB\R2009B\BIN\MEX.PL: Error: 'Files\Microsoft' not found.

------------------

It looks like the space is not allowed for the Matlab.

So, I moved all folders to the simple name, and tried again.

But, I got a message as like below.

------------------

>> mex sfun.c -LC:\user\sdk3_5\Lib -lWS2_32.lib

Warning: MEX could not find the library "WS2_32.lib"

specified with -l option on the path specified

with the -L option.

Creating library C:\USERS\SKKIM\APPDATA\LOCAL\TEMP\MEX_9B~1\templib.x and object C:\USERS\SKKIM\APPDATA\LOCAL\TEMP\MEX_9B~1\templib.exp

sfun.obj : error LNK2019: unresolved external symbol __imp_listen referenced in function mdlInitializeConditions

sfun.obj : error LNK2019: unresolved external symbol __imp_bind referenced in function mdlInitializeConditions

sfun.obj : error LNK2019: unresolved external symbol __imp_socket referenced in function mdlInitializeConditions

sfun.obj : error LNK2019: unresolved external symbol __imp_htonl referenced in function mdlInitializeConditions

sfun.obj : error LNK2019: unresolved external symbol __imp_htons referenced in function mdlInitializeConditions

sfun.obj : error LNK2019: unresolved external symbol __imp_WSAStartup referenced in function mdlInitializeConditions

sfun.mexw64 : fatal error LNK1120: 6 unresolved externals

C:\PROGRA~1\MATLAB\R2009B\BIN\MEX.PL: Error: Link of 'sfun.mexw64' failed.

-------------------------

I thought the Matlab did not recognize the library file.

If you inform me any clue, it would be great help.

Thanks

Friedrich 2011-7-20

I am not a great friend of copying libraries. What happens when you compile it this way:

mex('-v','sfun.c','-LC:\Program Files\Microsoft SDKs\Windows\v7.0\Lib\x64','-lWS2_32')

Please do not specify the .lib since the doc states:

On Windows systems, name expands to name.lib or libname.lib and on UNIX systems, to libname.so or libname.dylib.

Sangkyun Kim 2011-7-21

Your comment works perfectly.

I did not know .lib is not necessary.

Thank you! Fridrich

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