Post any defects you find in the released or beta versions of the ImageMagick software here. Include the ImageMagick version, OS, and any command-line required to reproduce the problem. Got a patch for a bug? Post it here.
In Imagemagick 7, you should append composite with magick (magick composite) otherwise you are actually using IM 6.
Nevertheless, using IM 6.9.10.6 and IM 7.0.8.6 Mac OSX Sierra and trying both composite and convert syntax, the only one that works properly is IM 6 convert.
That does not solve the basic issue, especially with convert. If the convert command above works in IM 6 it should work in IM 7. This define was never needed before. Why should one need to add this define, now? None of my images have clip paths.
There are differences between IMv6 and IMv7 per the porting guide. However, we do try to replicate IMv6 behavior in IMv7 whenever possible. We have a patch to fix the -dissolve option problem you reported. Until the patch is exported, use the -define as we proposed.
Some -compose methods can modify the 'destination' image outside the overlay area. It is disabled by default. You can enable this by setting the special -set 'option:compose:clip-to-self' to 'true'.