ARM VERSION 1.2 Guide de l'utilisateur télécharger pdf (Page 45)

int f() {

S s(2); // initialize 's'

asmfunc(&s); // call 'asmfunc' so it

// can change 's'

return s.i * 3;

}

Example 4-16 Defining the assembly language function

AREA Asm, CODE

EXPORT asmfunc

asmfunc ; the definition of the Asm

LDR r1, [r0] ; function to be called from C++

ADD r1, r1, #5

STR r1, [r0]

MOV pc, lr

END

Calling C++ from C

Example 4-17 and Example 4-18 show how to call C++ from C.

Example 4-17 Defining the function to be called in C++

struct S { // has no base classes or virtual functions

S(int s) : i(s) { }

int i;

};

extern "C" void cppfunc(S *p) {

// Definition of the C++ function to be called from C.

// The function is written in C++, only the linkage is C

p->i += 5; //

}

Example 4-18 Declaring and calling the function in C

struct S {

int i;

};

extern void cppfunc(struct S *p);

/* Declaration of the C++ function to be called from C */

int f(void) {

struct S s;

s.i = 2; /* initialize 's' */

cppfunc(&s); /* call 'cppfunc' so it */

/* can change 's' */

return s.i * 3;

}

Calling C++ from assembly language

Example 4-19 and Example 4-20 show how to call C++ from assembly language.

Example 4-19 Defining the function to be called in C++

struct S { // has no base classes or virtual functions

S(int s) : i(s) { }

int i;

};

extern "C" void cppfunc(S * p) {

// Definition of the C++ function to be called from ASM.

// The body is C++, only the linkage is C

p->i += 5;

}

In ARM assembly language, import the name of the C++ function and use a Branch with link instruction to call it:

Example 4-20 Defining assembly language function

AREA Asm, CODE

IMPORT cppfunc ; import the name of the C++

; function to be called from Asm

EXPORT f

Mixing C, C++, and Assembly Language

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ARM VERSION 1.2 Guide de l'utilisateur Page 45

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