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This function is called to get the address of the C library errno variable when the C library attempts to read or write errno. The library provides a default implementation. It is unlikely that you have to reimplement this function.

This function is not part of the C library standard, but is supported by the ARM C library as an extension.


This function is associated with pre-ABI versions of the compilation tools. However, it remains supported to ensure that object files compiled with those tools link successfully. Unless you are working with object files compiled with pre-ABI versions of the tools, use __aeabi_errno_addr() instead of __rt_errno_addr().


volatile int *__rt_errno_addr(void);
Copyright © 2011-2012 ARM. All rights reserved.ARM DUI 0589B

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