C/C ++ hybrid programming

 

In C, Calling C ++ in C ++ will use extern "C", but the meaning of the two is quite different !!

 

 

 

 

First, we will introduce how to call C in C ++, which is familiar to everyone:

 

Example:

 

// C code

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;"> void foo (int x );

</Span>

 

// C ++ code

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;"> // C ++ code

Extern "C" void foo (int x );

</Span> enables the C ++ connector to search for this function through a symbol similar to _ foo, rather than a symbol similar to _ foo_int.

 

 

The use of extern "C" tells the compiler to compile the encapsulated interface in the C method. Of course, the C ++ syntax in the interface function is still compiled in the C ++ mode. The use of extern "C" tells the compiler to compile the encapsulated interface in the C method. Of course, the C ++ syntax in the interface function is still compiled in the C ++ mode.

 

 

 

 

Let's talk about calling C ++ in C, which also uses extern "C". This tells the compiler to compile the encapsulation interface in C mode, of course, the C ++ syntax in the interface function is still compiled in C ++ mode.

 

C ++ Code: (non-member functions)

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;"> extern "C" int foo (int x );

Int foo (int x)

{

//...

} </Span> in this way, the compiler will compile the foo function into a symbol similar to the _ foo symbol instead of the _ foo_int symbol.

 

 

 

C code

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;"> int foo (int x );

Void cc (int x)

{

Foo (x );

//...

} </Span>

 

 

 

 

If you want to call member functions (including virtual functions) in C, you need to provide a simple wrapper ). For example:

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;"> // C ++ code:

 

Class C

 

{

 

//...

 

Virtual double f (int );

 

};

 

 

 

Extern "C" double call_C_f (C * p, int I) // wrapper function

 

{

 

Return p-> f (I );

 

} </Span>

Then, you can call C: f ():

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;">/* C code :*/

 

Double call_C_f (struct C * p, int I );

 

 

 

Void ccc (struct C * p, int I)

 

{

 

Double d = call_C_f (p, I );

 

/*...*/

 

} </Span>

 

 

 

 

 

 

If you want to call a overload function in C, you must provide the packaging of different names to be called by C code. For example:

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;"> // C ++ code:

 

Void f (int );

 

Void f (double );

 

 

 

Extern "C" void f_ I (int I) {f (I );}

 

Extern "C" void f_d (double d) {f (d) ;}</span>

Then, you can use f () for each overload as follows ():

 

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;">/* C code :*/

 

Void f_ I (int );

 

Void f_d (double );

 

 

 

Void cccc (int I, double d)

 

{

 

F_ I (I );

 

F_d (d );

 

/*...*/

 

} </Span>

 

 

 

 

 

References:

 

Bjarne Stroustrup's original link address is http://www.research.att.com /~ Bs/bs_faq2.html # callCpp

 

 

 

 

 

 

 

The following example describes how C calls C ++:

 

<Span style = "font-family: Microsoft YaHei; font-size: 18px;"> // cpp. h

# Ifndef _ cpp_h __

# Define _ cpp_h __

 

Class class1 {

Class1 ();

~ Class1 ();

Public:

Int I;

Int J;

 

Int getI (void );

};

 

# Endif

// End file

 

// Cpp. cpp

# I nclude "stdafx. h"

# I nclude <iostream>

# I nclude "cpp. h"

# I nclude "c. h"

 

Using namespace std; // open the standard library namespace

 

Class1: class1 ()

{}

 

Class1 ::~ Class1 ()

{}

 

Int class1: getI (void)

{

Return I ++;

}

 

// Compile the following function by calling C

Extern "C"

Int get_class1_ I (struct1 * p)

{

Class1 * pClass1 = (class1 *) p;

 

Cout <"c ++:" <pClass1-> getI () <endl;

 

Return pClass1-> getI ();

}

 

// End file

 

// C. h

# Ifndef _ c_h __

# Define _ c_h __

 

# Ifdef _ cplusplus

Extern "C "{

# Endif

 

Typedef struct {

Int I; // consistent with the variables in the class1 class

Int j;

} Struct1;

 

# Ifdef _ cplusplus

}

# Endif

# Endif

// End file

 

// C. c

# I nclude <cstdio>

# I nclude "c. h"

 

Extern int get_class1_ I (void * p );

 

Struct1 s;

 

Int main (void)

{

Printf ("c: % d \ n", get_class1_ I (& s ));

Printf ("c: % d \ n", get_class1_ I (& s ));

 

Return 0;

}

 

// End file </span> in linux, run:

 

Gcc-c. c

G ++-c cpp. cpp

Gcc-lstdc ++ c. o cpp. o-o result