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Use eventfd() function with uClibc

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The Boost eventfd code either directly makes the eventfd system call

using __NR_eventfd (when __GLIBC_MINOR is less than 8), or otherwise

uses the eventfd() function provided by the C library.

​

However, since uClibc pretends to be glibc 2.2, the Boost eventfd code

directly uses the system call. While it works fine on most

architectures, it doesn't on ARC since __NR_eventfd is not defined on

this architecture. However, eventfd() is properly implemented.

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So, this patch adjusts the logic used by Boost to consider uClibc as a

C library providing the eventfd() function.

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Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

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Index: b/boost/asio/detail/impl/eventfd_select_interrupter.ipp

===================================================================

--- a/boost/asio/detail/impl/eventfd_select_interrupter.ipp

+++ b/boost/asio/detail/impl/eventfd_select_interrupter.ipp

@@ -23,7 +23,7 @@

 #include <sys/stat.h>

 #include <sys/types.h>

 #include <fcntl.h>

-#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8

+#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8 && !defined(__UCLIBC__)

 # include <asm/unistd.h>

 #else // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8

 # include <sys/eventfd.h>

@@ -46,7 +46,7 @@

 void eventfd_select_interrupter::open_descriptors()

 {

-#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8

+#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8 && !defined(__UCLIBC__)

   write_descriptor_ = read_descriptor_ = syscall(__NR_eventfd, 0);

   if (read_descriptor_ != -1)

   {