C++: Initial .qhelp file

cpp/ql/src/Best Practices/Likely Errors/CommaBeforeMisleadingIndentation.cpp

@@ -0,0 +1,32 @@
+/*
+ * Here, the comma should have been a semicolon:
+ */
+
+enum privileges entitlements = NONE;
+
+if (is_admin)
+    entitlements = FULL, // BAD
+
+restrict_privileges(entitlements);
+
+/*
+ * This is misleading, because the code is unexpectedly equivalent to:
+ */
+
+enum privileges entitlements = NONE;
+
+if (is_admin) {
+    entitlements = FULL;
+    restrict_privileges(entitlements);
+}
+
+/*
+ * Whereas the following code was probably intended:
+ */
+
+enum privileges entitlements = NONE;
+
+if (is_admin)
+    entitlements = FULL; // GOOD
+
+restrict_privileges(entitlements);

cpp/ql/src/Best Practices/Likely Errors/CommaBeforeMisleadingIndentation.qhelp

@@ -4,11 +4,17 @@
 <qhelp>
 
 <overview>
-<p>...</p>
+<p>
+If the expression to the right of a comma operator starts at an earlier column than the expression to the left, then
+this suspicious indentation likely indicates a logic error caused by a typo that may escape visual inspection.
+</p>
 </overview>
 
 <recommendation>
-<p>...</p>
+<p>
+Use standard indentation around the comma operator: begin the right-hand-side operand at the same level of
+indentation as the left-hand-side operand.
+</p>
 </recommendation>
 
 <example>