It's definitely a lot harder than in the USA. As a consequence companies often opt not to hire engineers directly if they want more flexibility but instead go through third party companies to contract developers (the infamous "SSII"). It's more expensive but you can get rid of them basically whenever you want.

I generally in favor of the French model (over, say, the American one) but I do think that in this case it's probably a bit overprotective for certain more privileged jobs. A software developer these days shouldn't have too much trouble finding a new job if they get fired, I wouldn't mind trading some of that social security for higher pay for instance.