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| Home > Compiler-specific Features > __semihost intrinsic | ||||
This intrinsic inserts an SVC or BKPT instruction into the instruction stream generated by the compiler. It enables you to make semihosting calls from C or C++ that are independent of the target architecture.
int __semihost(int val, const void
*ptr)
Where:
Is the request code for the semihosting request.
See Developing Software for ARM Processors for more information.
Is a pointer to an argument/result block.
See Developing Software for ARM Processors for more information.
See Developing Software for ARM Processors for more information on the results of semihosting calls.
Use this intrinsic from C or C++ to generate the appropriate semihosting call for your target and instruction set:
0x123456In ARM state for all architectures.
0xABIn Thumb state, excluding M-profile architectures. This behavior is not guaranteed on all debug targets from ARM or from third parties.
0xABFor M-profile architectures (Thumb only).
ARM processors prior to ARMv7 use SVC instructions to make
semihosting calls. However, if you are compiling for a Cortex M-profile processor,
semihosting is implemented using the BKPT instruction.
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 r1,|L1.12|
MOVS r0,#1
SVC #0xab
...
|L1.12|
...
buffer
% 400
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