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Diffstat (limited to 'www/cxx_compatibility.html')
| -rw-r--r-- | www/cxx_compatibility.html | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/www/cxx_compatibility.html b/www/cxx_compatibility.html index bd48c6c..fe03240 100644 --- a/www/cxx_compatibility.html +++ b/www/cxx_compatibility.html @@ -42,14 +42,25 @@ C++-conformance bug in your code and how you can fix it.</p> <h2 id="vla">Variable-length arrays</h2> <!-- ======================================================================= --> -<p>GCC allows an array's size to be determined at run time. This, -however, is not standard C++. Furthermore, it is a potential security -hole as an incorrect array size may overflow the stack. If Clang tells -you <tt>"variable length arrays are not permitted in C++"</tt>, here -are some ways in which you can fix it:</p> +<p>GCC and C99 allow an array's size to be determined at run +time. This extension is not permitted in standard C++. However, Clang +supports such variable length arrays in very limited circumstances for +compatibility with GNU C and C99 programs:</p> + +<ul> + <li>The element type of a variable length array must be a POD + ("plain old data") type, which means that it cannot have any + user-declared constructors or destructors, base classes, or any + members if non-POD type. All C types are POD types.</li> + + <li>Variable length arrays cannot be used as the type of a non-type +template parameter.</li> </ul> + +<p>If your code uses variable length arrays in a manner that Clang doesn't support, there are several ways to fix your code: <ol> -<li>replace it with a fixed-size array if you can determine a +<li>replace the variable length array with a fixed-size array if you can + determine a reasonable upper bound at compile time; sometimes this is as simple as changing <tt>int size = ...;</tt> to <tt>const int size = ...;</tt> (if the definition of <tt>size</tt> is a compile-time |
