Messages in this thread Patch in this message | | | Date | Tue, 8 Sep 2015 07:45:25 +0200 | Subject | Re: Use (two) different compilers at build-time? | From | Sedat Dilek <> |
| |
On Tue, Sep 8, 2015 at 12:30 AM, Sedat Dilek <sedat.dilek@gmail.com> wrote: > On Mon, Sep 7, 2015 at 11:20 PM, Sedat Dilek <sedat.dilek@gmail.com> wrote: >> On Mon, Sep 7, 2015 at 10:59 PM, Linus Torvalds >> <torvalds@linux-foundation.org> wrote: >>> On Mon, Sep 7, 2015 at 1:53 PM, Sedat Dilek <sedat.dilek@gmail.com> wrote: >>>> >>>> That does not work. >>> >>> .. because you didn't do what I told you to do. >>> >>>> I copied a gcc-compiled percpu.o OR deleted/renamed percpu.o and >>>> re-invoked make - this starts a complete new build from scratch. >>> >>> Right. Because you changed the compiler name, so now the build system >>> realizes that the old build instructions are stale. >>> >>> Which is why you have to: >>> >>>>> Use a wrapper around the compiler (and point to that wrapper with the >>>>> "to switch compilers from under the make, without the build paths >>>>> changing (because otherwise our makefile auto-machinery notices that >>>>> flags and command changed). >>>>> >>>>> Use CC (or CROSS_COMPILE) to point at your wrapper. >>>> >>>> No idea how to realize that, sorry. >>> >>> Literally just do something like this: >>> >>> - have a shell script call "mycompiler" and make it do gcc/llvm "$@". >>> >>> - or even just use a symlink (the script has the advantage that you >>> can play with the options etc too) >>> >>> - change the shell script (or symlink) itself, and make sure to use >>> the same CC for "make" at all times, so that the build script never >>> sees that the underlying command is now different. >>> >>> It should work fine, I've done it a couple of times (although >>> admittedly not recently) >>> >> >> OK, I have created a mycompiler shell-script and use that for CC and >> HOSTCC in my own build-script. >> >> Using CLANG... >> >> [ /usr/bin/mycompiler ] >> >> #!/bin/bash >> >> clang "$@" >> - EOF - >> >> $ mycompiler --version >> clang version 3.7.0 (tags/RELEASE_370/final) >> Target: x86_64-unknown-linux-gnu >> Thread model: posix >> >> Switching to GCC... >> >> [ /usr/bin/mycompiler ] >> >> #!/bin/bash >> >> gcc-4.9 "$@" >> - EOF - >> >> $ mycompiler --version >> gcc-4.9 (Ubuntu 4.9.2-0ubuntu1~12.04) 4.9.2 >> Copyright (C) 2014 Free Software Foundation, Inc. >> This is free software; see the source for copying conditions. There is NO >> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. >> >> Thanks, that helped me a lot. >> > > Sadly, this trick does not work here with Linux v4.2. >
So, the problem is any change to your make-lines. Means $COMPILER and/or compiler flags!
I simplified in Makefile...
COMPILER := clang export COMPILER
and then did a symlink gcc-4.9 -> clang.
This did NOT work because clang uses a compiler-flag '-no-integrated-as' which does not exist for gcc!
So, switching from gcc -> clang or vice-versa is not possible with your compiler-wrapper-script trick :-(.
Anyway, I need a different solution.
One of my ideas was to hack the mm/Makefile.
--- a/mm/Makefile +++ b/mm/Makefile @@ -2,6 +2,9 @@ # Makefile for the linux memory manager. #
+COMPILER := gcc +export COMPILER + KASAN_SANITIZE_slab_common.o := n KASAN_SANITIZE_slub.o := n
@@ -78,3 +81,6 @@ obj-$(CONFIG_CMA) += cma.o obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o + +COMPILER := clang +export COMPILER Not sure if this works.
- Sedat -
| |