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Compiler Reference Guide

Conventions and Feedback Introduction Compiler Command-line Options Language Extensions Compiler-specific Features Keywords and operators __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)) function attribute __attribute__((always_inline)) function attribute __attribute__((const)) function attribute __attribute__((constructor[(priority)])) function __attribute__((deprecated)) function attribute __attribute__((destructor[(priority)])) function a __attribute__((format_arg(string-index))) function __attribute__((malloc)) function attribute __attribute__((noinline)) function attribute __attribute__((nomerge)) function attribute __attribute__((nonnull)) function attribute __attribute__((noreturn)) function attribute __attribute__((notailcall)) function attribute __attribute__((pcs("calling_convention") __attribute__((pure)) function attribute __attribute__((section("name"))) functio __attribute__((unused)) function attribute __attribute__((used)) function attribute __attribute__((visibility("visibility_type&qu __attribute__((weak)) function attribute __attribute__((weakref("target"))) funct Type attributes __attribute__((bitband)) type attribute __attribute__((aligned)) type attribute __attribute((packed)) type attribute __attribute__((transparent_union)) type attribute Variable attributes __attribute__((alias)) variable attribute __attribute__((at(address))) variable attribute __attribute__((aligned)) variable attribute __attribute__((deprecated)) variable attribute __attribute__((noinline)) constant variable attrib __attribute__((packed)) variable attribute __attribute__((section("name"))) variabl __attribute__((transparent_union)) variable attrib __attribute__((unused)) variable attribute __attribute__((used)) variable attribute __attribute__((visibility("visibility_type&qu __attribute__((weak)) variable attribute __attribute__((weakref("target"))) varia __attribute__((zero_init)) variable attribute Pragmas #pragma anon_unions, #pragma no_anon_unions #pragma arm #pragma arm section [section_type_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 exceptions_unwind, #pragma no_exceptions_u #pragma hdrstop #pragma import symbol_name #pragma import(__use_full_stdio) #pragma import(__use_smaller_memcpy) #pragma inline, #pragma no_inline #pragma no_pch #pragma Onum #pragma once #pragma Ospace #pragma Otime #pragma pack(n) #pragma pop #pragma push #pragma softfp_linkage, #pragma no_softfp_linkage #pragma thumb #pragma unroll [(n)] #pragma unroll_completely #pragma weak symbol, #pragma weak symbol1 = symbol Instruction intrinsics __breakpoint intrinsic __cdp intrinsic __clrex intrinsic __clz intrinsic __current_pc intrinsic __current_sp intrinsic __disable_fiq intrinsic __disable_irq intrinsic __enable_fiq intrinsic __enable_irq intrinsic __fabs intrinsic __fabsf intrinsic __force_stores intrinsic __ldrex intrinsic __ldrexd intrinsic __ldrt intrinsic __memory_changed intrinsic __nop intrinsic __pld intrinsic __pldw intrinsic __pli intrinsic __promise intrinsic __qadd intrinsic __qdbl intrinsic __qsub intrinsic __rbit intrinsic __rev intrinsic __return_address intrinsic __ror intrinsic __schedule_barrier intrinsic __semihost intrinsic __sev intrinsic __sqrt intrinsic __sqrtf intrinsic __ssat intrinsic __strex intrinsic __strexd intrinsic __strt intrinsic __swp intrinsic __usat intrinsic __wfe intrinsic __wfi intrinsic __yield intrinsic ARMv6 SIMD intrinsics ETSI basic operations C55x intrinsics VFP status intrinsic __vfp_status intrinsic Fused Multiply Add (FMA) intrinsics Named register variables Predefined macros Built-in function name variables C and C++ Implementation Details Semihosting ARMv6 SIMD Instruction Intrinsics Via File Syntax Standard C Implementation Definition Standard C++ Implementation Definition C and C++ Compiler Implementation Limits

Compiler Reference Guide

__semihost intrinsic

__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.

Show/hideSyntax

int __semihost(int val, const void *ptr)

where:

val

Is the request code for the semihosting request.

ptr

Is a pointer to an argument/result block.

See Semihosting for more information about these parameters.

Show/hideReturn value

See Semihosting for more information on the results of semihosting calls.

Show/hideUsage

Use this intrinsic from C or C++ to generate the appropriate semihosting call for your target and instruction set:

SVC 0x123456

In ARM state for all architectures.

SVC 0xAB

In Thumb state, excluding M-profile architectures. This behavior is not guaranteed on all debug targets from ARM or from third parties.

BKPT 0xAB

For M-profile architectures (Thumb only).

Show/hideRestrictions

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.

Show/hideExample

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

Show/hideSee also

Copyright © 2007-2008, 2011-2012 ARM. All rights reserved.ARM DUI 0376D
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