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#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 [no_]exceptions_unwind

#pragma hdrstop

#pragma import symbol_name

#pragma [no_]inline

#pragma [no_]softfp_linkage

#pragma unroll [(n)]

#pragma unroll_completely

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__strex

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__strex

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Version 3.1

Home > Compiler-specific Features > Instruction intrinsics > __strex

4.7.39. `__strex`

This intrinsic inserts an instruction of the form STREX{size} into the instruction stream generated by the compiler. It enables you to use a STREX instruction in your C or C++ code to store data to memory.

Syntax

int __strex(unsigned int val, volatile void *ptr)

Where:

val

Is the value to be written to memory.

ptr

Points to the address of the data to be written to in memory. To specify the size of the data to be written, cast the parameter to an appropriate integral type.

Table 4.10. Access widths supported by the __strex intrinsic

Instruction	Size of data loaded	C cast
`STREXB`	unsigned byte	`(`char `*)`
`STREXH`	unsigned halfword	`(`short int `*)`
`STREX`	word	`(`int `*)`

Return value

The __strex intrinsic returns:

0: if the STREX instruction succeeds
1: if the STREX instruction is locked out.

Errors

The compiler does not recognize the __strex intrinsic when compiling for a target that does not support the STREX instruction. The compiler generates either a warning or an error in this case.

The __strex intrinsic does not support access to doubleword data. The compiler generates an error if you specify an access width that is not supported.

Example

int foo(void)
{
    int loc=0xff;

    return(!__strex(0x20, (volatile char *)loc));
}

Compiling this code with the command‑line option --device=DLM produces

||foo|| PROC
        MOVS     r1,#0xff
        MOVS     r0,#1
        MOVS     r3,#0x20
        STREXB   r2,r3,[r1]
        CMP      r2,#0
        BEQ      |L1.24|
        MOVS     r0,#0
|L1.24|
        BX       lr
        ENDP

See also

__ldrex
LDREX and STREX in the Assembler Guide.

Copyright © 2007 ARM Limited. All rights reserved.	ARM DUI 0376A
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