New to C++ programming I am trying to get some open source software running so I can build upon it.
I have 3 *cpp modules. One contains...
const double Qcf[6]= { 1.0, 448.831, 0.64632,0.02832, 28.317, 2.4466};
The other two modules make use of this constant and have a reference to it included in their body
extern double Qcf[];
Each of these modules then has a method/ function
i.e. something like
void routine1()
{
double i;
i = 2 * Qcf[1];
}
I have built the code and it appears that it has compiled (i.e. the *cpp goes to obj) but I get 2 error messages.
LNK2001 unresolved external symbol "double Qcf"
Each error pertains to each of the *obj files
(I also get another LNK1120 Two unresolved externals error, but I think if I solve the LNK2001 issue this will self correct).
Any advice on how to correct this is appreciated in advance.
Qcf is defined as a const double[] in one module, and declared as double[] in the other. You should declare it const too.
(or std::array<double, 6> instead of a C-style array, if your compiler supports C++11)
Related
I'm migrating a XLL from 32-Bit to 64-Bit with VS2015 and C++.
I started changing the datatypes. So I switched 'int' to '_int64'.
CPP_XLOPER Create_XLOperHeader_form_Str(const wchar_t*aBegin,_int64 strlen,bool aTranspose){
static CPP_XLOPER xlDefault(L" ");
_int64 l = strlen;
and it throws me the error:
Error
LNK2001 unresolved external symbol
"class CPP_XLOPER __cdecl Create_XLOperTable_from_Str(wchar_t const *,__int64,bool,bool)"
(?Create_XLOperTable_from_Str##YA?AVCPP_XLOPER##PEB_W_J_N2#Z)
I guess I have to modify 'class CPP_XLOPER', isn't it?
Any hint much appreciated,
thx in advance;
surplus
The method linker is complaining about has last two parameters of type bool - ...,int64,bool,bool), while the one you have modified has only one last parameter of type bool. Either you have deleted another existing method, or you have also removed one bool from the implementation (and only you know if this was or was not intentional). But yeah, in general you should fix the function declaration to match the definition.
I was very surprised when I tried to search this error as I got only 4 results, two of which seem to be in Chinese. I am getting this error when compiling my project and boost sources alltogether. I searched the boost library and found this:
namespace boost
{
/*
This file is a "null" implementation of tss cleanup; it's
purpose is to to eliminate link errors in cases
where it is known that tss cleanup is not needed.
*/
void tss_cleanup_implemented(void)
{
/*
This function's sole purpose is to cause a link error in cases where
automatic tss cleanup is not implemented by Boost.Threads as a
reminder that user code is responsible for calling the necessary
functions at the appropriate times (and for implementing an a
tss_cleanup_implemented() function to eliminate the linker's
missing symbol error).
If Boost.Threads later implements automatic tss cleanup in cases
where it currently doesn't (which is the plan), the duplicate
symbol error will warn the user that their custom solution is no
longer needed and can be removed.
*/
}
}
My question is what's tss cleanup, why is it needed and how do I implement it.
I don't know about TSS, but to fix this linker error, you need to define
BOOST_THREAD_WIN32
and
BOOST_THREAD_BUILD_LIB
so boost/thread/src/win32/tss_pe.cpp implements the missing function (empty).
I assume there are few results on the Internet for this question, because the build scenario is rare. Most people do not build boost within their own project, but build boost with b2.
This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 7 years ago.
I am debugging some C++ software, and want to modify an existing function slightly, so that it changes the value of a particular variable used elsewhere in the program.
The function is currently defined as so:
void DataStore::setEraseSelected(){
...
// Function code here
...
}
As it stands, the function works correctly with no problems whatsoever. But, I now want to modify the function, so that it will change the value of a variable used elsewhere in the program. To do this, I have tried passing the variable into the function as a parameter (I have also updated the header file to reflect the changes to the function), and then assigning a value to the variable inside the function:
void DataStore::setEraseSelected(toAMS::DataMessage statusMsg){
...
// Function code here
...
statusMsg.CODE_ERASE = Types::Activated;
...
}
As mentioned, I have added the declaration to the header file, so that it now has the declaration for the function with the parameter, as well as the one for the function without the parameter:
void DataStore::setEraseSelected(toAMS::DataMessage statusMsg);
But when I try and build the code (using Visual Studio 2010), I get the following two compile errors:
error LNK2001: unresolved external symbol "public void_thiscall DataStore::setEraseSelected(void)" (? setEraseSelected#DataStore::QAEXXZ)
error LNK1120: 1 unresolved externals
The first error highlights the project .obj file, which I have tried deleting and building again, but get the same error, and second one highlights the project .exe file, which I have also tried deleting and building again, but get the same error.
Anyone have any ideas why? I've had a look on SO for questions regarding these errors, but none of them seem to clearly explain why I might be getting them. They all seem to suggest that the compiler is possibly looking in the wrong place, but if I undo my changes, then the code compiles with no problems, and I haven't told the compiler to look anywhere else when building the code with my changes...
void DataStore::setEraseSelected(int );
Pass that variable
I have try all solutions appeared on the web, but the error still exist.
Here are the error information:
error LNK2019: unresolved external symbol _gluOrtho2D#16 referenced in function "protected: virtual void __thiscall widget::initializeGL(void)" (?initializeGL#widget##MAEXXZ)
I am sure that I have included all the head files correctly, and link files are in their right position, and I also add #define GLUT_DISABLE_ATEXIT_HACK in my file. Besides, when I didn't use Qt, every thing is OK. While I put my code into QGLWidget, the error appeared!
Any more, I noticed that the error information after _gluOrtho2D# is 16, not 32 as other's on the web...
Why? How to correct them?
To answer your question regarding the 16 following the decorated _gluOrhto2D#, that is the size of the argument list you are passing (in bytes) when using the __stdcall calling convention.
Considering gluOrtho2D (...) is supposed to take 4 GLdouble arguments and GLdouble is supposed to be a 64-bit type something seems seriously wrong (the proper decorated name is _gluOrtho2D#32).
Did you by any chance confuse your compiler by attempting to pass gluOrtho2D (...) 4 GLfloat / float variables and/or re-define the prototype for gluOrtho2D (...) anywhere?
I am doing c++ porting/development in visual studios 2008.
I am getting the following issues.
1) Variable sized array not allowed.
2) Linking error for any of the undefined functions of the class even if they are not referenced.(error LNK2001: unresolved external symbol "public: virtual void __thiscall ...)
I think these are related to the version of the c++ language VS2008 support.
I am trying a compile and link large c++ codebase. I cannot substitute variable sized array with new/alloc. Please give me solution so that I can use the existing code.
Can anyone please help me sort this out?
But the following code works fine in the same VS2008
class Hello
{
public:
int a;
public:
virtual void add();
};
class bye : public Hello
{
public:
int y;
public:
void add();
};
int main()
{
std::cout << "got";
}
Where am I going wrong?
Virtual functions are considered "used" if you have a single instance of a class created anywhere. Your link error indicate that certain virtual functions are not implemented. As the error list all of them by name it must be a trivial task to locate them, end figure out if you failed to include some code, compiled with different options, or they were indeed unimplemented in the source place -- in which case you can just add blank implementations calling terminate.
For the VLA problem: that extemsion is not present in VS2008, period. Even if you wait some years and VS201y will implement the new VLA-like thing in C++14, it will not go back to your chosen compiler. (kinda weird if you ask me to chose a 5-year old bug-ridden beast that has dropped of support long ago, instead of the current...)
But std::vector does almost the same as VLA, and if you find difference you can write a beter wrapper or a few adapter functions. The place of memory allocation is not something you can discover legally in the program anyway. In case you'd hit some performance bottleneck, that is doubtful from such a change, you can rearrange a small portion of code.
How about use std::vector to replace the arrays?