Date: Sun, 21 Jun 2015 01:05:47 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: [PATCH v9] Build process uses script to add CFI directives to x86 asm On Sun, Jun 21, 2015 at 07:00:57AM +0200, Alex wrote: > > > > > > I think someone mentioned this before -- this still fails to apply CFI > > to the asm files obtained via the .sub/SUBARCH system (see the rules > > just above the ones you changed). Of course I don't really like > > duplicating complex rules, and i386 has no SUBARCHs anyway, so perhaps > > we could put off changing this if someone has an idea for how to > > eliminate the extra rules for SUBARCHs when we overhaul the build > > system... > > > > This was intentional, but since it has come up so many times, I will add > the (extraneous) rules for SUBARCHs. Would doing it with a new AS_CMD variable work and make sense? That would also eliminate the duplication in logic for .o vs .lo too, I think... > > I'd still like to check $CFLAGS in addition to $CFLAGS_AUTO, since > > CFLAGS=-g is the usual way I ask for debug info. (I'm sorry I ever > > added the --enable-debug option to configure. :) > > OK, will do. Thanks! > > I haven't reviewed the awk script much at all, but as long as it seems > > to work in practice I'm okay with committing it. One thing I would > > like to ask though -- is it pretty robust against bad things happening > > if it sees new asm constructs it's not expecting? I'd just like to > > avoid regressions if we add new asm later, where it becomes necessary > > to delay commits to asm in order to fix bugs in the CFI generation. > > > It passes all your asm through and simply adds debugging directives when it > recognizes certain constructs. So in no case will it actually break the > asm. The worst which will happen is that you will adjust the stack pointer > in some obscure way that it doesn't recognize, no CFI directive will be > added, and then a debugger will be unable to produce a stack trace at that > point in the code. But this is no worse than what we have right now. Right > now we don't do anything to help the debugger at all. Alright, sounds good. If all the build system integration issues are worked out then I think this will be ready to commit. Rich
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