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__align __alignof__ __ALIGNOF__ __asm __forceinline __global_reg __inline __int64 __INTADDR__ __irq __packed __pure __smc __softfp __svc __svc_indirect __svc_indirect_r7 __value_in_regs __weak __writeonly __declspec attributes __declspec(dllexport) __declspec(dllimport) __declspec(noinline) __declspec(noreturn) __declspec(nothrow) __declspec(notshared) __declspec(thread) Function attributes __attribute__((alias)) __attribute__((always_inline)) __attribute__((const)) __attribute__((deprecated)) __attribute__((malloc)) __attribute__((noinline)) __attribute__((noreturn)) __attribute__((pure)) __attribute__((section)) __attribute__((unused)) __attribute__((used)) __attribute__((weak)) Type attributes __attribute__((aligned)) __attribute((packed)) __attribute__((transparent_union)) Variable attributes __attribute__((alias)) __attribute__((at(address))) __attribute__((aligned)) __attribute__((deprecated)) __attribute__((packed)) __attribute__((section)) __attribute__((transparent_union)) __attribute__((unused)) __attribute__((used)) __attribute__((weak)) __attribute__((zero_init)) Pragmas #pragma [no_]anon_unions #pragma arm #pragma arm section [section_sort_list] #pragma diag_default tag[,tag,...] #pragma diag_error tag[,tag,...] #pragma diag_remark tag[,tag,...] #pragma diag_suppress tag[,tag,...] #pragma diag_warning tag[, tag, ...] #pragma [no_]exceptions_unwind #pragma hdrstop #pragma import symbol_name #pragma [no_]inline #pragma no_pch #pragma Onum #pragma once #pragma Ospace #pragma Otime #pragma pop #pragma push #pragma [no_]softfp_linkage #pragma unroll [(n)] #pragma unroll_completely #pragma thumb Instruction intrinsics __breakpoint __builtin_clz __builtin_constant_p __builtin_expect __builtin_frame_address __builtin_return_address __builtin_popcount __cdp __clrex __clz __current_pc __current_sp __disable_fiq __disable_irq __enable_fiq __enable_irq __fabs __fabsf __force_stores __ldrex __ldrt __memory_changed __nop __pld __pli __qadd __qdbl __qsub __rbit __rev __return_address __ror __schedule_barrier __semihost __sev __sqrt __sqrtf __ssat __strex __strt __swp __usat __wfe __wfi __yield ARMv6 SIMD intrinsics ETSI basic operations C55x intrinsics Named register variables Compiler predefines Predefined macros Function names C and C++ Implementation Details Via File Syntax Standard C Implementation Definition Standard C++ Implementation Definition C and C++ Compiler Implementation Limits__semihost
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Home > Compiler-specific Features > Instruction intrinsics > __semihost | |||
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(intval, const void *ptr)
Where:
valIs the request code for the semihosting request.
ptrIs a pointer to an argument/result block.
See Appendix A Semihosting in the Compiler User Guide 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:
SVC 0x123456In ARM state for all architectures.
SVC 0xABIn Thumb state, excluding ARMv7‑M. This behavior is not guaranteed on all debug targets from ARM or from third parties.
BKPT 0xABFor ARMv7‑M, Thumb‑2 only.
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.
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
BKPT in the Assembler Guide
SVC in the Assembler Guide
Appendix A Semihosting in the Compiler User Guide.
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