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Compiler-specific Features

Keywords and operators

__svc

__svc_indirect_r7

__value_in_regs

__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__((no_instrument_function))

__attribute__((nomerge))

__attribute__((nonnull))

__attribute__((noreturn))

__attribute__((notailcall))

__attribute__((pure))

__attribute__((section("name")))

__attribute__((unused))

__attribute__((used))

__attribute__((visibility("visibility_type")))

__attribute__((weak))

Type attributes

__attribute__((bitband))

__attribute__((aligned))

__attribute((packed))

__attribute__((transparent_union))

Variable attributes

__attribute__((alias))

__attribute__((at(address)))

__attribute__((aligned))

__attribute__((deprecated))

__attribute__((packed))

__attribute__((section("name")))

__attribute__((transparent_union))

__attribute__((unused))

__attribute__((used))

__attribute__((visibility("visibility_type")))

__attribute__((weak))

__attribute__((zero_init))

#pragma anon_unions, #pragma no_anon_unions

#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 exceptions_unwind, #pragma no_exceptions_u

#pragma hdrstop

#pragma import symbol_name

#pragma import(__use_full_stdio)

#pragma inline, #pragma no_inline

#pragma pack(n)

#pragma softfp_linkage, #pragma no_softfp_linkage

#pragma unroll [(n)]

#pragma unroll_completely

Instruction intrinsics

__memory_changed

__return_address

__schedule_barrier

ARMv6 SIMD intrinsics

ETSI basic operations

C55x intrinsics

Named register variables

VFP status intrinsic

GNU builtin functions

Nonstandard functions

C99 functions in the C90 reserved namespace

C99 floating-point functions

Other builtin functions

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C and C++ Implementation Details

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Standard C++ Implementation Definition

C and C++ Compiler Implementation Limits

__svc

RealView Compilation Tools for µVision Compiler Reference Guide

Version 4.0

Home > Compiler-specific Features > Keywords and operators > __svc

4.1.15. `__svc`

The __svc keyword declares a SuperVisor Call (SVC) function taking up to four integer-like arguments and returning up to four results in a value_in_regs structure.

__svc is a function qualifier. It affects the type of a function.

Syntax

__svc(int svc_num) return-type function-name([argument-list]);

Where:

svc_num

Is the immediate value used in the SVC instruction.

It is an expression evaluating to an integer in the range:

0 to 2²⁴–1 (a 24-bit value) in an ARM instruction
0-255 (an 8-bit value) in a 16-bit Thumb instruction.

Usage

This causes function invocations to be compiled inline as an AAPCS-compliant operation that behaves similarly to a normal call to a function.

The __value_in_regs qualifier can be used to specify that a small structure of up to 16 bytes is returned in registers, rather than by the usual structure-passing mechanism defined in the AAPCS.

Example

__svc(42) void terminate_1(int procnum); // terminate_1 returns no results
__svc(42) int terminate_2(int procnum);  // terminate_2 returns one result
typedef struct res_type
{
    int res_1;
    int res_2;
    int res_3;
    int res_4;
} res_type;
__svc(42) __value_in_regs res_type terminate_3(int procnum);
                                         // terminate_3 returns more than
                                         // one result

Errors

When an ARM architecture variant or ARM architecture-based processor that does not support an SVC instruction is implied on the command line using the --device option, the compiler generates an error.

See also

__value_in_regs
SVC in the Assembler Guide.

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