Date: Wed, 21 Feb 2018 16:38:25 +0900 From: Masahiro Yamada <yamada.masahiro@...ionext.com> To: Ulf Magnusson <ulfalizer@...il.com> Cc: Sam Ravnborg <sam@...nborg.org>, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arnd Bergmann <arnd@...db.de>, Kees Cook <keescook@...omium.org>, Randy Dunlap <rdunlap@...radead.org>, Michal Marek <michal.lkml@...kovi.net>, Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>, kernel-hardening@...ts.openwall.com, Jonathan Corbet <corbet@....net>, sparclinux@...r.kernel.org, Linux-sh list <linux-sh@...r.kernel.org>, X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Rich Felker <dalias@...c.org>, Jeff Dike <jdike@...toit.com>, "H. Peter Anvin" <hpa@...or.com>, user-mode-linux-devel@...ts.sourceforge.net, Yoshinori Sato <ysato@...rs.sourceforge.jp>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, linuxppc-dev@...ts.ozlabs.org, Paul Mackerras <paulus@...ba.org>, user-mode-linux-user@...ts.sourceforge.net, Ingo Molnar <mingo@...hat.com>, "David S. Miller" <davem@...emloft.net>, Michael Ellerman <mpe@...erman.id.au>, "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Richard Weinberger <richard@....at>, Emese Revfy <re.emese@...il.com> Subject: Re: [PATCH 00/23] kconfig: move compiler capability tests to Kconfig 2018-02-20 0:18 GMT+09:00 Ulf Magnusson <ulfalizer@...il.com>: >> >> I'm not happy that we in one context can reference CONFIG variables >> directly, but inside the $(call ...) and $(shell ...) needs the $ prefix. >> But I could not come up with something un-ambigious where this could be avoided. > > I think we should be careful about allowing references to config > symbols. It mixes up the parsing and evaluation phases, since $() is > expanded during parsing (which I consider a feature and think is > needed to retain sanity). > > Patch 06/23 removes the last existing instance of symbol references in > strings by getting rid of 'option env'. That's an improvement to me. > We shouldn't add it back. This is really important design decision, so I'd like to hear a little more from experts. For example, x86 allows users to choose sub-arch, either 'i386' or 'x86_64'. https://github.com/torvalds/linux/blob/v4.16-rc2/arch/x86/Kconfig#L4 If the user toggles CONFIG_64BIT, the bi-arch compiler will work in a slightly different mode (at least, back-end parts) So, my question is, is there a case, $(cc-option, -m32 -foo) is y, but $(cc-option, -m64 -foo) is n ? (or vice versa) If the answer is yes, $(cc-option -foo) would have to be re-calculated every time CONFIG_64BIT is toggled. This is what I'd like to avoid, though. -- Best Regards Masahiro Yamada
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