[llvm] r202728 - Clarify struct usage guidelines
Duncan P. N. Exon Smith
dexonsmith at apple.com
Mon Mar 3 08:48:45 PST 2014
Author: dexonsmith
Date: Mon Mar 3 10:48:44 2014
New Revision: 202728
URL: http://llvm.org/viewvc/llvm-project?rev=202728&view=rev
Log:
Clarify struct usage guidelines
The current coding standards restrict the use of struct to PODs, but no
one has been following them. This patch updates the standards to
clarify when structs are dangerous and describe common practice in LLVM.
Modified:
llvm/trunk/docs/CodingStandards.rst
Modified: llvm/trunk/docs/CodingStandards.rst
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/CodingStandards.rst?rev=202728&r1=202727&r2=202728&view=diff
==============================================================================
--- llvm/trunk/docs/CodingStandards.rst (original)
+++ llvm/trunk/docs/CodingStandards.rst Mon Mar 3 10:48:44 2014
@@ -650,12 +650,38 @@ members public by default.
Unfortunately, not all compilers follow the rules and some will generate
different symbols based on whether ``class`` or ``struct`` was used to declare
-the symbol. This can lead to problems at link time.
+the symbol (e.g., MSVC). This can lead to problems at link time.
-So, the rule for LLVM is to always use the ``class`` keyword, unless **all**
-members are public and the type is a C++ `POD
-<http://en.wikipedia.org/wiki/Plain_old_data_structure>`_ type, in which case
-``struct`` is allowed.
+* All declarations and definitions of a given ``class`` or ``struct`` must use
+ the same keyword. For example:
+
+.. code-block:: c++
+
+ class Foo;
+
+ // Breaks mangling in MSVC.
+ struct Foo { int Data; };
+
+* As a rule of thumb, ``struct`` should be kept to structures where *all*
+ members are declared public.
+
+.. code-block:: c++
+
+ // Foo feels like a class... this is strange.
+ struct Foo {
+ private:
+ int Data;
+ public:
+ Foo() : Data(0) { }
+ int getData() const { return Data; }
+ void setData(int D) { Data = D; }
+ };
+
+ // Bar isn't POD, but it does look like a struct.
+ struct Bar {
+ int Data;
+ Foo() : Data(0) { }
+ };
Do not use Braced Initializer Lists to Call a Constructor
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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