[libcamera-devel] [PATCH] ipa: raspberrypi: Fix crash under LTO

[Dave Jones]

Hi Laurent,

On Fri, Mar 10, 2023 at 12:40:33PM +0200, Laurent Pinchart wrote:
[snip]
>> -static std::map<std::string, CamHelperCreateFunc> camHelpers;
>> +namespace {
>> +
>> +std::map<std::string, CamHelperCreateFunc> &camHelpers()
>> +{
>> +	static std::unique_ptr<std::map<std::string, CamHelperCreateFunc>> obj =
>> +		std::make_unique<std::map<std::string, CamHelperCreateFunc>>();
>> +	return *obj;
>
>I think you could simply write
>
>	static std::map<std::string, CamHelperCreateFunc> helpers;
>	return helpers;

That would likely be fine, but I thought I'd just note that in my 
original patch [1] I'd actually used "new" with a pointer instead of a 
static object quite deliberately. As my C++ skills are caked in the dust 
of grime of numerous years of neglect, I'd consulted the C++ FAQ and 
noted that using a static pointer opens the possibility of a crash on 
deinit [2] (I'm not certain it *would* crash, but I figured I'd take the 
easy/safe way out and leave the OS to deal with the memory) by using the 
solution posited at [3].

[1]: https://github.com/raspberrypi/libcamera/pull/46/files

[2]: https://isocpp.org/wiki/faq/ctors#construct-on-first-use-v2

[3]: https://isocpp.org/wiki/faq/ctors#static-init-order-on-first-use

That *might* be preferable, though I admit it looks ... somewhat ugly.

Cheers,

Dave Jones.