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linker error with externed value

I am getting a 2019 linker error followed by a 1120 when I try to access matrix lut_max in a thread. I externed the value in the thread (thus leading to the error) becuase I was getting an unknown identifier error without it. The reason I do not create the table in the thread is becuase I only need to create it once, and the thread would create it multiple times. I wrote a function that writes the table once from my GUI. I instatiate the class with

FxLUT FxLUTInst;

Then I call the function

FxLUTINst.WriteTable();

All the class and function do is write the table, no erros there.

My extern statement is:

extern CvMat* lut_mat;

I am sure that this is something simple or simly done wrong. Please help.

Thanks

WLE

error in full:

C:\...\OpenCVThread1.obj [Error LNK2019] unresolved external symbol "struct CvMat * lut_mat" (?lut_mat@@3PAUCvMat@@A) referenced in function "public: virtual void * __thiscall OpenCVThread::Entry(void)" (?Entry@OpenCVThread@@UAEPAXXZ)

SOLUTION

efn

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ASKER CERTIFIED SOLUTION

Infinity08

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SOLUTION

rstaveley

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Wanderinglazyeye

ASKER

Here is what I have now, still with some errors:

.cpp
----------------------
class FxLUT
{

private :
CvMat *lut_mat;

public:
FxLUT();
~FxLUT();

bool WriteLUT();
CvMat *getMat() { return lut_mat; }

};

.h
---------------

FxLUT::FxLUT()
{
}

FxLUT::~FxLUT()
{
}

//function to create lookup table

bool FxLUT::WriteLUT()
{

uchar lut[256];
CvMat* lut_mat;
lut_mat = cvCreateMatHeader( 1, 256, CV_8UC1 );
cvSetData( lut_mat, lut, 0 ); //set the matrix data to NULL
for(int i = 0; i < 256; i++ )
{
if ((i>105)&&(i<117))
{
lut[i] = i;
}
else
{
//nada
}
}

return true;
}

call from the GUI:
---------------------------

I am getting an error with CVMat *LutMat and the return lut_mat statement. To clarify, CVMat is an open cv function. What is the error in my coding?

rstaveley

Do you want a local...

CvMat* lut_mat;

...in WriteLUT? Try commenting it out.

SOLUTION

Infinity08

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Wanderinglazyeye

ASKER

Ok sorry about the .cpp & .h mix up.

Here is again with errors:

.h
---------------------------

class FxLUT
{

private :
CvMat *lut_mat; //LINE 29

public:
FxLUT();
~FxLUT();

bool WriteLUT();
CvMat *getMat() { return lut_mat; } //LINE 37

};

.cpp
--------------------------
using namespace std;

extern CvMat *LutMat

FxLUT::FxLUT()
{
}

FxLUT::~FxLUT()
{
}

//function to create lookup table

bool FxLUT::WriteLUT()
{

uchar lut[256];
//CvMat* lut_mat;
lut_mat = cvCreateMatHeader( 1, 256, CV_8UC1 );
cvSetData( lut_mat, lut, 0 ); //set the matrix data to NULL
for(int i = 0; i < 256; i++ )
{
if ((i>105)&&(i<117))
{
lut[i] = i;
}
else
{
//nada
}
}

return true;
}

ABC.cpp //main gui, write - call just once
-----------
...
static FxLUT FxLUTInst;

...

FxLUTInst.WriteLUT();

Thread.cpp
-------------------

access LUT table here

errors line 37:
37 c:\...\LUT.h [Error C2143] syntax error : missing ';' before '*'
37 c:\...\LUT.h [Error C4430] missing type specifier - int assumed. Note: C++ does not support default-int
37 c:\...\\LUT.h [Error C4430] missing type specifier - int assumed. Note: C++ does not support default-int
37 c:\...\LUT.h [Warning C4183] 'getMat': missing return type; assumed to be a member function returning 'int'
37 c:\...\LUT.h [Error C2065] 'lut_mat' : undeclared identifier

line 29:
29 c:\...\\LUT.h [Error C2143] syntax error : missing ';' before '*'
29 c:\...\LUT.h [Error C4430] missing type specifier - int assumed. Note: C++ does not support default-int
29 c:\...\\LUT.h [Error C4430] missing type specifier - int assumed. Note: C++ does not support default-int

SOLUTION

efn

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Infinity08

So, does it work now ? What code do you have ?

It should be something like this :

---- fxlut.h ----

#include "the_include_for_cvmat.h"

class FxLUT
{

private :
CvMat *lut_mat; //LINE 29

public:
FxLUT();
~FxLUT();

bool WriteLUT();
CvMat *getMat() { return lut_mat; } //LINE 37

};

---- ----

---- fxlut.cpp ----

#include "fxlut.h"

FxLUT::FxLUT()
{
}

FxLUT::~FxLUT()
{
}

//function to create lookup table

bool FxLUT::WriteLUT()
{

uchar lut[256];
//CvMat* lut_mat;
lut_mat = cvCreateMatHeader( 1, 256, CV_8UC1 );
cvSetData( lut_mat, lut, 0 ); //set the matrix data to NULL
for(int i = 0; i < 256; i++ )
{
if ((i>105)&&(i<117))
{
lut[i] = i;
}
else
{
//nada
}
}

return true;
}

---- ----

---- ABC.cpp ---- //main gui, write - call just once

#include "fxlut.h"
...
static FxLUT FxLUTInst;

...

FxLUTInst.WriteLUT();

---- ----

---- Thread.cpp ----

#include "fxlut.h"

extern FxLUT FxLUTInst;

void theThreadFunction() {
CvMat *theMatrix = FxLUTInst.getMat();
// use the matrix ...
}

---- ----