As part of the work on PR66192 I promised a doc update at some point -
here's that - hopefully better late than never.
I also wonder if this is worth putting into the documentation in
addition to our release notes though I couldn't convince myself that
standards.texi was the right place for it- any other suggestions are
welcome.
OK ?
regards
Ramana
Index: htdocs/gcc-6/changes.html
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<h2>Caveats</h2>
+ <ul>
+ <li>On bare-metal targets for architectures like ARM
+ that have a relaxed memory model, the compiler will generate
+ code that calls <code>__sync_synchronize</code> for thread-safety
+ of guard accesses for statics in C++ code. In these cases,
+ it is expected that the user will provide either a stub function to
+ implement <code>__sync_synchronize</code> to provide a memory
+ barrier instruction or would compile their application with
+ <code>-fno-threadsafe-statics</code> as may be appropriate.
+ This can be demonstrated with the example in
+ <a href="https://gcc.gnu.org/PR66192";>PR66192</a>
+ for the <code>arm-none-eabi</code> target, with the option
+ <code>-mcpu=arm7tdmi</code> on the command line. </li>
+ </ul>
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<h2 id="general">General Optimizer Improvements</h2>
