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Diffstat (limited to 'docs/CodingStandards.html')
| -rw-r--r-- | docs/CodingStandards.html | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/docs/CodingStandards.html b/docs/CodingStandards.html index ff00c81673..a2420805ec 100644 --- a/docs/CodingStandards.html +++ b/docs/CodingStandards.html @@ -29,6 +29,7 @@ <li><a href="#ci_warningerrors">Treat Compiler Warnings Like Errors</a></li> <li><a href="#ci_portable_code">Write Portable Code</a></li> + <li><a href="#ci_rtti_exceptions">Do not use RTTI or Exceptions</a></li> <li><a href="#ci_class_struct">Use of <tt>class</tt>/<tt>struct</tt> Keywords</a></li> </ol></li> </ol></li> @@ -406,6 +407,28 @@ libSystem.</p> <!-- _______________________________________________________________________ --> <div class="doc_subsubsection"> +<a name="ci_rtti_exceptions">Do not use RTTI or Exceptions</a> +</div> +<div class="doc_text"> + +<p>LLVM does not use RTTI (e.g. dynamic_cast<>) or exceptions, in an +effort to reduce code and executable size. These two language features violate +the general C++ principle of "you only pay for what you use", causing executable +bloat even if exceptions are never used in a code base, or if RTTI is never used +for a class. Because of this, we turn them off globally in the code. +</p> + +<p> +That said, LLVM does make extensive use of a hand-rolled form of RTTI that use +templates like <a href="ProgrammersManual.html#isa">isa<>, cast<>, +and dyn_cast<></a>. This form of RTTI is opt-in and can be added to any +class. It is also substantially more efficient than dynamic_cast<>. +</p> + +</div> + +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> <a name="ci_class_struct">Use of <tt>class</tt> and <tt>struct</tt> Keywords</a> </div> <div class="doc_text"> |