warnings when compiling libev with clang

Benjamin Kaduk kaduk at MIT.EDU
Tue Nov 5 03:07:25 CET 2013

On Tue, 5 Nov 2013, Marc Lehmann wrote:

> On Mon, Nov 04, 2013 at 04:25:55PM -0500, Benjamin Kaduk <kaduk at MIT.EDU> wrote:
>> I was doing some warning cleanup on a project that ships a bundled
>> version of libev (krb5), and figured that I should note the changes I
>> made in my working copy here, to see if they held interest for the
>> libev maintainers.
> Please see the documentation section "COMPILER WARNINGS". What you are
> trying to do is pretty pointless.

Thanks for the pointer, I am something of a libev newbie.

Though, what I did was clearly useful for my short-term goal: analyze my 
own application's code.  Eliminating warnings from imported code reduces 
"noise" in the log so that I can get to the interesting parts which affect 
my own code.  There are lots of ways I could have done so, with patching 
the code being just one of them.  The whole point of my first mail was to 
find out whether what I had done would additionally have long-term value. 
That decision is yours, and I have no reason to try very much to affect 
it. (I have no interest in maintaining a separate patchset atop libev just 
to remove harmless warnings, as implied by the mindset implied by your 

>> (3) The file-local function fd_rearm_all() is defined but never used.
>> It can safely be removed to eliminate this compiler warning.
> It's used in most backends, actually, as a simple grep would have
> shown. Eliminating it makes them not compile. Thats what you get for
> blindly working around compiler warnings.

It was sufficient for my purpose at the time.

A simple grep would not be enough, one would need to find the part where 
the different backend codes are included via the preprocessor instead of 
being compiled as separate objects. The idiom of using the preprocessor to 
include .c files is not one I encounter very often (the style guides in my 
main projects frown on it); removing the 'static' keyword from the 
function definition would probably help people like me who are unfamiliar 
with the code gain a better/faster understanding of it (in addition to 
eliminating the warning which drew my attention to it).  Yes, it would 
cause a symbol to escape the object's linkage, that's your tradeoff to 
analyze.  (It sounds like your decision is already made; please don't take 
the above as an effort to sway your decision, it's just an explanation of 
my mindset/thought process.)

>> I'll put links to the commits that I used to implement these fixes below.
> At least your report indicates that clang can compile libev again - that's
> progress.

Well, this is with the clang 3.2 rev 170710 included in the FreeBSD base 
system from a svn snapshot from some time ago, compiling the embedded 
libev 4.04 from the krb5 tree.  Advances in either libev or clang could 
have rendered this datapoint useless.

I will say once more that I do think that the parenthesis around the 
bitwise operators (trimmed from the context) is very helpful for readers 
of the code, and ask for its inclusion.  The rest of these patches are not 
really useful for anything other than removing warnings, and ignoring them 
is fine by me.

Thanks for the input,


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