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Compiler Command-line Options

Language Extensions

Compiler-specific Features

Keywords and operators

__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

Compiler predefines

Predefined macros

C and C++ Implementation Details

Via File Syntax

Standard C Implementation Definition

Standard C++ Implementation Definition

C and C++ Compiler Implementation Limits

attribute((packed))

RealView Compilation Tools for µVision Compiler Reference Guide

Version 4.0

Home > Compiler-specific Features > Variable attributes > __attribute__((packed))

4.5.5. `attribute((packed))`

The packed variable attribute specifies that a variable or structure field has the smallest possible alignment. That is, one byte for a variable, and one bit for a field, unless you specify a larger value with the aligned attribute.

Note

This variable attribute is a GNU compiler extension that is supported by the ARM compiler.

Example

struct
{
    char a;
    int b __attribute__ ((packed));
} Variable_Attributes_packed_0;

See also

#pragma pack(n)
Packed structures
The __packed qualifier and unaligned data access in the Compiler User Guide
__packed structures versus individually __packed fields in the Compiler User Guide.

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