[Interest] iOS libpng conflicts with another lib

[maitai]

Hello,

I have an external lib build statically into my qt app (5.9.4, 
widget-based). That lib can optionally support internally png images. If 
I activate this, there is no problems in other platforms (I tested 
Android, Windows, Linux, Raspberry, MacOS), but on iOS as soon as I try 
to open a png image with a QPixmap or a QImage it crashes. If I compile 
my external lib without png support no more crash.

So it appears that libpng from Qt and the one from my lib are 
conflicting, but only on iOS.

Any idea why this occurs on iOS and what I could do to avoid the crash? 
I badly need png support in both qt and the external lib.

Thanks
Philippe