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<div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
I am not clear whether your volatile is a file level or function level variable<br>
i.e. does your code look like this...</div>
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BEFORE</div>
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Data buffer[buffersize];</div>
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void func() {</div>
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volatile S v = { buffer, m2, ... };</div>
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}</div>
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AFTER<br>
<br>
<span style="margin:0px;font-size:12pt"> void func() {</span>
<div style="margin:0px;font-size:12pt"><br>
</div>
<div style="margin:0px;font-size:12pt"> volatile S v;</div>
<div style="margin:0px;font-size:12pt"> </div>
<div style="margin:0px;font-size:12pt"> v.m1 = buffer;</div>
<div style="margin:0px;font-size:12pt"> <span style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)">v.m2 = m2;</span></div>
<div style="margin:0px;font-size:12pt"> ...<br>
tell_someone_they_can_use_v_to_access_buffer(&v);</div>
<div style="margin:0px;font-size:12pt"><br>
</div>
<div style="margin:0px;font-size:12pt"> }</div>
<span style="margin:0px;font-size:12pt"></span><br>
OR like this <br>
<br>
<span style="margin:0px;font-size:12pt"> Data buffer[buffersize];</span>
<div style="margin:0px;font-size:12pt"><span style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)"> volatile S v; // old code = { buffer, m2, ... };</span>
<div style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)"><br>
</div>
</div>
<div style="margin:0px;font-size:12pt"> void func() {</div>
<div style="margin:0px;font-size:12pt"> // new code</div>
<div style="margin:0px;font-size:12pt"><span style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)"> v.m1 = buffer;</span>
<div style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)"> <span style="margin:0px;background-color:rgb(255, 255, 255)">v.m2 = m2;</span></div>
<div style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)"> ...<br>
tell_someone_they_can_use_v_to_access_buffer(&v);</div>
<div style="margin:0px;font-size:12pt;background-color:rgb(255, 255, 255)"><span style="font-size: 12pt;"> }</span><br>
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<span style="margin:0px;font-size:12pt"></span><br>
Which is v? a global or a function local?<br>
<br>
<span style="background-color:rgb(255, 255, 255);display:inline !important">Perhaps you have a race between the initialization and use of v.</span></div>
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<br>
<span style="background-color:rgb(255, 255, 255);display:inline !important">The initialization of non-function statics and globals happens in C++ in a somewhat unpredictable order, but before main() is called, as the complicated description you linked to describes.<br>
</span><br>
<span style="background-color:rgb(255, 255, 255);display:inline !important">Also I suspect buffer should be volatile.</span></div>
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<br>
/Bevin</div>
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