User guide

ManualsBrandsARM ManualsComputer HardwareVERSION 1.2

they have no base classes or virtual functions. If such a struct has neither a user-defined copy assignment

operator or a user-defined destructor, it is a POD structure.

• References are represented as pointers.

• Pointers to data members and pointers to member functions occupy four bytes. They have the same null pointer

representation as normal pointers.

• No distinction is made between pointers to C functions and pointers to C++ (non-member) functions.

Symbol name mangling

ARM C++ mangles external names of functions and static data members in a manner similar to that described in

section 7.2c of Ellis, M.A. and Stroustrup, B., The Annotated C++ Reference Manual (1990). The linker unmangles

symbols in messages.

C names must be declared as extern "C" in C++ programs. This is done already for the ARM ANSI C headers.

Refer to Using C header files from C++ for more information.

4.4.3 Examples

The following sections contain code examples that demonstrate:

• Calling assembly language from C

• Calling C from assembly language

• Calling C from C++

• Calling assembly language from C++

• Calling C++ from C

• Calling C++ from assembly language

• Calling C++ from C or assembly language

• Passing a reference between C and C++.

The examples assume the default non software-stack checking ATPCS variant because they perform stack

operations without checking for stack overflow.

Calling assembly language from C

Example 4-9 and Example 4-10 show a C program that uses a call to an assembly language subroutine to copy one

string over the top of another string.

Example 4-9 Calling assembly language from C

#include <stdio.h>

extern void strcopy(char *d, const char *s);

int main()

{ const char *srcstr = "First string - source ";

char dststr[] = "Second string - destination ";

/* dststr is an array since we're going to change it */

printf("Before copying:\n");

printf(" %s\n %s\n",srcstr,dststr);

strcopy(dststr,srcstr);

printf("After copying:\n");

printf(" %s\n %s\n",srcstr,dststr);

return (0);

}

Example 4-10 Assembly language string copy subroutine

AREA SCopy, CODE, READONLY

EXPORT strcopy

strcopy ; r0 points to destination string.

; r1 points to source string.

LDRB r2, [r1],#1 ; Load byte and update address.

STRB r2, [r0],#1 ; Store byte and update address.

CMP r2, #0 ; Check for zero terminator.

BNE strcopy ; Keep going if not.

MOV pc,lr ; Return.

END

Example 4-9 is located in install_directory\examples\asm as strtest.c and scopy.s. Follow these steps

to build the example from the command line:

1. Type armasm -g scopy.s to build the assembly language source.

Mixing C, C++, and Assembly Language