using c++ function in c

Question

hi! im working on a project in C. but i have to use my function that i have written in C++. how can i implemented this function to my project.

i see some extern declarations but i couldnt implemented it. i tried to use like that.

extern "C" int save(int size, char *fileName, short int *recordBuffer1)

{

}

Thanks

---

Ayhan KÜÇÜKMANİSA

Answer 1

Could you provide a little more information?  What compiler are you using?    Is the C++ function written in it's own .cpp file?  If so, why not just add it to the project in Visual Studio - unless of course you are using some other non-IDE compiler?

Answer 2

im using visual studio 2008. im adding this function with add menu to project. but how can i call this function from "main.c"?

---

Ayhan KÜÇÜKMANİSA

Answer 3

In the main.c file you just need the prototype (forward declaration) like this:

 

int save(int size, char *fileName, short int *recordBuffer1);

 

void main()

{

  int x;

  short int * rb;

  x = save(10, "myfile.txt", rb);

}

Answer 4

mr_jeff wrote:

In the main.c file you just need the prototype (forward declaration)  like this:

int save(int size, char *fileName, short int *recordBuffer1);

void main()
{
int x;
short int * rb;
x = save(10, "myfile.txt", rb);
}

Here's a techniqe for writing headers that can be included both in C and  C++ sources:

// save.h

#ifdef __cplusplus
extern "C" {
#endif

int save(int size, char *fileName, short int *recordBuffer1)

#ifdef __cplusplus
}
#endif

Now you can include save.h both in main.c and in save.cpp (where you no  longer need to write extern "C").

---

Igor Tandetnik

Answer 5

mr_jeff wrote:

In the main.c file you just need the prototype (forward declaration)  like this:

int save(int size, char *fileName, short int *recordBuffer1);

void main()
{
int x;
short int * rb;
x = save(10, "myfile.txt", rb);
}

Here's a techniqe for writing headers that can be included both in C and  C++ sources:

// save.h

#ifdef __cplusplus
extern "C" {
#endif

int save(int size, char *fileName, short int *recordBuffer1)

#ifdef __cplusplus
}
#endif

Now you can include save.h both in main.c and in save.cpp (where you no  longer need to write extern "C").

---

Igor Tandetnik

In this case though I don't think he wants the extern "C" part though because the function "save" is written in C++, right?

Answer 6

mr_jeff wrote:

In this case though I don't think he wants the extern "C" part though  because the function "save" is written in C++, right?

He does, if he wants it to be callable from C. All extern "C" does is  suppress C++ name mangling. Without it, C compiler will say "main.obj  needs a function named _save", and C++ compiler will say "save.obj has a  function available, named save@XYZ123" (or whatever its mangled name  turns out to be). Then the linker will complain about unresolved  externals.

---

Igor Tandetnik

Answer 7

mr_jeff wrote:

In this case though I don't think he wants the extern "C" part though  because the function "save" is written in C++, right?

He does, if he wants it to be callable from C. All extern "C" does is  suppress C++ name mangling. Without it, C compiler will say "main.obj  needs a function named _save", and C++ compiler will say "save.obj has a  function available, named save@XYZ123" (or whatever its mangled name  turns out to be). Then the linker will complain about unresolved  externals.

---

Igor Tandetnik

That's why I only have one medal next to my name.  :)  So for his solution he will have to put the extern "C" business in his C++ file, right?  Then in main.c he doesn't use the extern "C"?  Is that right?

Answer 8

mr_jeff wrote:

mr_jeff wrote:

In this case though I don't think he wants the extern "C" part  though because the function "save" is written in C++, right?

He does, if he wants it to be callable from C. All extern "C" does is  suppress C++ name mangling. Without it, C compiler will
say "main.obj needs a function named _save", and C++ compiler will  say "save.obj has a function available, named save@XYZ123"
(or whatever its mangled name turns out to be). Then the linker will  complain about unresolved externals. 

That's why I only have one medal next to my name. :) So for his  solution he will have to put the extern "C" business in his C++
file, right? Then in main.c he doesn't use the extern "C"? Is that  right?

Yes, extern "C" goes into C++ code, never into C code. C compiler would  consider it a syntax error. However, as I've shown, you can use  preprocessor tricks to expose extern "C" to C++ compiler while hiding it  from C compiler, all in the same file.

---

Igor Tandetnik

Answer 9

Thanks. i implement c++ function to my code. now i can call function from main.c

---

Ayhan KÜÇÜKMANİSA