update coding standards. Partial specialization is now ok,

[oota-llvm.git] / docs / CodingStandards.html

diff --git a/docs/CodingStandards.html b/docs/CodingStandards.html
index e3ec3ff136c743d56004cd64bd867c7d83714a1e..44a55a55857548133d99fa24c2cd8346a65dda72 100644 (file)
--- a/docs/CodingStandards.html
+++ b/docs/CodingStandards.html
@@ -397,9 +397,10 @@ portable code.  If there are cases where it isn't possible to write portable
 code, isolate it behind a well defined (and well documented) interface.</p>
 
 <p>In practice, this means that you shouldn't assume much about the host
-compiler, including its support for "high tech" features like partial
-specialization of templates.  If these features are used, they should only be
-an implementation detail of a library which has a simple exposed API.</p>
+compiler, and Visual Studio tends to be the lowest common denominator.
+If advanced features are used, they should only be an implementation detail of 
+a library which has a simple exposed API, and preferably be buried in 
+libSystem.</p>
 
 </div>
 
@@ -851,6 +852,38 @@ return 0;
 </pre>
 </div>
 
+<p>Another issue is that values used only by assertions will produce an "unused
+ value" warning when assertions are disabled.  For example, this code will warn:
+</p>
+
+<div class="doc_code">
+<pre>
+  unsigned Size = V.size(); 
+  assert(Size &gt; 42 &amp;&amp; "Vector smaller than it should be");
+
+  bool NewToSet = Myset.insert(Value);
+  assert(NewToSet &amp;&amp; "The value shouldn't be in the set yet");  
+</pre>
+</div>
+
+<p>These are two interesting different cases: in the first case, the call to 
+V.size() is only useful for the assert, and we don't want it executed when
+assertions are disabled.  Code like this should move the call into the assert
+itself.  In the second case, the side effects of the call must happen whether
+the assert is enabled or not.  In this case, the value should be cast to void
+to disable the warning.  To be specific, it is preferred to write the code
+like this:</p>
+
+<div class="doc_code">
+<pre>
+  assert(V.size() &gt; 42 &amp;&amp; "Vector smaller than it should be");
+
+  bool NewToSet = Myset.insert(Value); (void)NewToSet;
+  assert(NewToSet &amp;&amp; "The value shouldn't be in the set yet");  
+</pre>
+</div>
+
+
 </div>
 
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