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<div class="moz-cite-prefix">On 9/12/2017 2:41 PM, Nagurne, James
via cfe-dev wrote:<br>
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<div class="WordSection1">
<p class="MsoNormal">Hello,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am a developer in the compiler division
(CodeGen) at Texas Instruments. Our compiler targets a variety
of embedded targets from DSPs like the C6000 to
microcontrollers like the C2000 and MSP430. All of our
compilers use a common, modified EDG C++ front end accepting a
majority of the C++14 standard in addition to many extensions
allowed by both GCC and Clang, such as __has_feature.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We’re investigating using libc++ in
addition to our home grown and augmented C (and C++
implementation-specific behavior) library to fill out our C++
support. Having worked on this for a week or so, I’ve
cultivated a list of issues whose answers/solutions will help
guide me in completing and trying to upstream some/all of this
work.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">- Atomic builtins (__sync functions) are
assumed to exist, and other atomic issues<o:p></o:p></p>
<p class="MsoNormal">Our first drop of C++14 will not have
support for threads or atomics, since we’re still talking with
other teams which support the low-level operations and APIs
needed.<o:p></o:p></p>
<p class="MsoNormal">The CMakelists.txt file checks for atomic
support, warning “Host compiler must support std::atomic”. Is
this a major problem that could stop us from being able to use
libc++ immediately?<o:p></o:p></p>
<p class="MsoNormal">For the __sync functions, we could define
template functions to overload and perform the elemental
operation without any guarantee of atomicity (I believe all
uses are currently ‘int’ operations). Is this alright,
assuming we will not be supporting multiple theads?</p>
</div>
</blockquote>
<br>
There's a CMake option LIBCXX_ENABLE_THREADS you can use to turn off
multi-threaded support... but you might still have trouble with
atomics. See <a class="moz-txt-link-freetext" href="https://reviews.llvm.org/D35235">https://reviews.llvm.org/D35235</a> .<br>
<br>
-Eli<br>
<pre class="moz-signature" cols="72">--
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project</pre>
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