[cfe-dev] Feature/opinion request

[Jordan Rose]

On Oct 11, 2012, at 4:39 , David Chisnall <David.Chisnall at cl.cam.ac.uk> wrote:

> On 11 Oct 2012, at 08:04, Unai Landa wrote:
> 
>> Hello, I have the idea of a flag that emulates D behavior on variable initialization, I mean initialize all members to 0 by default, and allow explicit modify this behavior on performance sensitive code.
>> 
>> I think this could be an interesting compilation flag or pragma.
>> 
>> What's your opinion?
> 
> I quite like this idea as a language feature, but it has limited use as a compiler-specific extension.  You can't write code that relies on this behaviour without becoming completely compiler-dependent, and it will hide bugs that will appear with other compilers.  Given the reality of C, I'd prefer improvements to the used-uninitialised warnings, if there are any cases that they still miss.  
> 
> Adding = 0 to a declaration is not much effort if required, and it's often useful to have a variable in an undefined state at the start so that the compiler can check that it is initialised in every code path.  It's easy for a default initialisation to accidentally propagate when it isn't intended.

This does seem like something a tool could do, though. Normally we have the '= 0' fixit on a note for -Wuninitialized; maybe we could have a mode where that particular fixit is applied anyway? (An extension to 'clang-check -fixit'?)

Just throwing out ideas!
Jordan