On Wed, Apr 14, 2021 at 3:15 PM David Laight <David.Laight@xxxxxxxxxx> wrote: > > From: Andrii Nakryiko > > Sent: 14 April 2021 21:02 > > > > While -Og is designed to work well with debugger, it's still inferior to -O0 > > in terms of debuggability experience. It will cause some variables to still be > > inlined, it will also prevent single-stepping some statements and otherwise > > interfere with debugging experience. So switch to -O0 which turns off any > > optimization and provides the best debugging experience. > > Surely the selftests need to use the normal compiler options > so the compiler is generating the same type of code. > Otherwise you are likely to miss out some instructions completely. > I don't know, it's not like I'm trying to validate that GCC is generating a valid assembly. And there is almost nothing in libbpf and selftests that relies on delicate timing, so I don't think we should worry about changing timing characteristics. And there is nothing performance-critical in libbpf logic itself either, for the most part. So I don't see much harm in running selftests in debug mode. > For normal code I actually prefer using -O2 when dubugging. > If/when you need to look at the generated code you can see > the wood for the trees, with -O0 the code is typically > full of memory read/write to/from the stack. Whenever I try debugging anything in selftest+libbpf+bpftool, if any of those components are built with -O2, it makes it almost impossible to figure anything out in debugger. So I always go back and force all of them to -O0. So that's what this patch is doing, so that I and others don't have to go through this every single time we need to debug something. > > About the only annoying thing is tail-calls. > They can get confusing. > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) >
