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Technical Support
On-Line Manuals
Compiler User Guide
Preface
Overview of the Compiler
Getting Started with the Compiler
Compiler Features
Compiler Coding Practices
Compiler Diagnostic Messages
Using the Inline and Embedded Assemblers of the AR
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(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__((deprecated)) function attribute
__attribute__((destructor[(priority)])) function a
__attribute__((format)) function attribute
__attribute__((format_arg(string-index))) function
__attribute__((malloc)) function attribute
__attribute__((noinline)) function attribute
__attribute__((no_instrument_function)) function a
__attribute__((nomerge)) function attribute
__attribute__((nonnull)) function attribute
__attribute__((noreturn)) function attribute
__attribute__((notailcall)) function attribute
__attribute__((nothrow)) function attribute
__attribute__((pcs("calling_convention"))) functio
__attribute__((pure)) function attribute
__attribute__((section("name"))) function attribut
__attribute__((sentinel)) function attribute
__attribute__((unused)) function attribute
__attribute__((used)) function attribute
__attribute__((visibility("visibility_type"))) fun
__attribute__((warn_unused_result))
__attribute__((weak)) function attribute
__attribute__((weakref("target"))) function attrib
Type attributes
__attribute__((bitband)) type attribute
__attribute__((aligned)) type attribute
__attribute__((packed)) 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"))) variable attribut
__attribute__((unused)) variable attribute
__attribute__((used)) variable attribute
__attribute__((visibility("visibility_type"))) var
__attribute__((weak)) variable attribute
__attribute__((weakref("target"))) variable attrib
__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 GCC system_header
#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
__dmb intrinsic
__dsb intrinsic
__enable_fiq intrinsic
__enable_irq intrinsic
__fabs intrinsic
__fabsf intrinsic
__force_loads intrinsic
__force_stores intrinsic
__isb intrinsic
__ldrex intrinsic
__ldrexd intrinsic
__ldrt intrinsic
__memory_changed intrinsic
__nop intrinsic
__pld intrinsic
__pli 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
GNU built-in functions
Predefined macros
Built-in function name variables
C and C++ Implementation Details
What is Semihosting?
Via File Syntax
Summary Table of GNU Language Extensions
Standard C Implementation Definition
Standard C++ Implementation Definition
C and C++ Compiler Implementation Limits
__attribute__((unused)) variable attribute
| Non-Confidential |  PDF version | ARM DUI0375H | ||
| ||||
| Home > Compiler-specific Features > __attribute__((unused)) variable attribute | ||||
9.66 __attribute__((unused)) variable attribute
Normally, the compiler warns if a variable is declared but is never referenced. This attribute informs the compiler that you expect a variable to be unused and tells it not to issue a warning if it is not used.
Note
This variable attribute is a GNU compiler extension that the ARM compiler supports.Example
void Variable_Attributes_unused_0()
{
static int aStatic =0;
int aUnused __attribute__((unused));
int bUnused;
aStatic++;
}
In this example, the compiler warns that
bUnused is declared but never
referenced, but does not warn about aUnused.Note
The GNU compiler does not give any warning.Related reference
| Non-Confidential | PDF version | ARM DUI0375H |
| Copyright © 2007, 2008, 2011, 2012, 2014-2016 ARM. All rights reserved. |
| Home > Compiler-specific Features > __attribute__((unused)) variable attribute |
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