[llvm-commits] [llvm] r164389 - /llvm/trunk/docs/CodingStandards.rst

[David Blaikie]

On Fri, Sep 21, 2012 at 10:58 AM, Matt Beaumont-Gay
<matthewbg at google.com> wrote:
> On Fri, Sep 21, 2012 at 10:47 AM, David Blaikie <dblaikie at gmail.com> wrote:
>> Author: dblaikie
>> Date: Fri Sep 21 12:47:36 2012
>> New Revision: 164389
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=164389&view=rev
>> Log:
>> Document "do not use defaults in covered switch-over-enum" coding standard.
>>
>> 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=164389&r1=164388&r2=164389&view=diff
>> ==============================================================================
>> --- llvm/trunk/docs/CodingStandards.rst (original)
>> +++ llvm/trunk/docs/CodingStandards.rst Fri Sep 21 12:47:36 2012
>> @@ -818,6 +818,24 @@
>>  will copy the vtable and RTTI into every ``.o`` file that ``#include``\s the
>>  header, bloating ``.o`` file sizes and increasing link times.
>>
>> +Don't use default labels in fully covered switches over enumerations
>> +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> +
>> +``-Wswitch`` warns if a switch, without a default label, over an enumeration
>> +does not cover every enumeration value. If you write a default label on a fully
>> +covered switch over an enumeration then the ``-Wswitch`` warning won't fire
>> +when new elements are added to that enumeration. To help avoid adding these
>> +kinds of defaults, Clang has the warning ``-Wcovered-switch-default`` which is
>> +off by default but turned on when building LLVM with a version of Clang that
>> +supports the warning.
>> +
>> +A knock-on effect of this stylistic requirement is that when building LLVM with
>> +GCC you may get warnings related "control may reach end of non-void function"
>
> Or "variable may be used uninitialized", if the switch is doing
> initialization, IIRC, but it may not be worth calling out separately.

Yeah, I figured it probably wasn't (& now that I look at it I'm having
trouble reproducing either the return or uninitialized use warnings in
GCC in simple examples... weird)

> Also, missing "to" after "related".

Added missing "to".

>> +if you return from each case of a covered switch-over-enum because GCC assumes
>> +that the enum expression may take any representable value, not just those in
>> +the enumeration.
>
> This might be phrased a little more clearly as "... not just those of
> individual enumerators."

Rephrased as suggested.

Changes committed in r164395.