RealView Compilation Tools Compiler Reference Guide - ARM ...

Compiler-specific Features
Usage
Use this intrinsic from C or C++ to generate the appropriate semihosting call for your
target and instruction set:
SVC 0x123456
SVC 0xAB
BKPT 0xAB
In ARM state for all architectures.
In Thumb state, excluding ARMv7-M. This behavior is not
guaranteed on all debug targets from ARM or from third parties.
For ARMv7-M, Thumb-2 only.
Restrictions
ARM processors prior to ARMv7 use SVC instructions to make semihosting calls.
However, if you are compiling for the Cortex-M3 processor, semihosting is
implemented using the BKPT instruction.
Example
char buffer[100];
...
void foo(void)
{
__semihost(0x01, (const void *)buf); // equivalent in thumb state to
// int __svc(0xAB) my_svc(int, int *);
// result = my_svc(0x1, &buffer);
}
Compiling this code with the option --thumb generates:
||foo|| PROC
...
LDR
MOVS
SVC
...
r1,|L1.12|
r0,#1
#0xab
|L1.12|
...
buffer
% 400
See also
• --cpu=list on page 2-15
• --thumb on page 2-86
• __svc on page 4-16
4-86 Copyright © 2007, 2010 ARM Limited. All rights reserved. ARM DUI 0348A
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