-ffast-math scrambles xulrunner

My previous difficulties with compiling Firefox 3 were because of the -ffast-math CFLAG, which was causing xulrunner to go nutty. Strange add-on messages, faulty form boxes and corrupted images, if you want to know how the patient presented himself.

I rebuilt firefox and xulrunner separately several times, with and without -ffast-math, with and without -O3, and with and without -Os, just for experimentation purposes. -ffast-math caused xulrunner to misbehave every time, regardless of the optimization level.

firefox itself was fine no matter what flags I used. And other ancillary packages seem to behave normally too. As far as -Os making programs load faster or run quicker, I don't notice anything substantially different over -O2. Since it's slightly more convenient not to have to switch flags for one package, I might stick with -Os -pipe -fomit-frame-pointer, and call it as good as it gets.

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