By default, the build (at least on Linux) uses its own bundled sysroot for
system libraries (glibc etc). The idea is to have a "hermetic build" that
works the same on all host machines, regardless of what's installed there.
use_sysroot=false turns that off and is, I think, required to make
is_clang=false work correctly. (I think our documentation mentions both
flags.)
On Wed, Sep 19, 2018 at 9:30 AM Graham Reeves <gra...@grahamreeves.com>
wrote:
> Aha! Exactly the bits of information I need. :)
>
> I'll give it a go shortly. If it doesn't go smoothly, I'll switch to
> docker and try the same for cross compiling on Linux.
>
> Does use_sysroot=false mean it's explicitly looking for CC/CXX instead of
> whatever is on the PATH, or is it for something different?
>
> I assumed the thing about gclient, but just wanted to be sure, given docs
> are explicit about "don't just clone" :)
>
> On Wed, 19 Sep 2018 at 5:19 pm, Jakob Kummerow <jkumme...@chromium.org>
> wrote:
>
>> I'm afraid we don't officially support cross-compiling on OSX, which
>> means it might work, but you're on your own. We'd be happy to accept
>> patches or documentation improvements, with community-maintained status.
>>
>> That said:
>>
>> I'd set is_clang=false and use_sysroot=false in args.gn, and set
>> CC/CXX/LINK via the environment. How far does that get you?
>>
>> target_os=["android"] in .gclient should not be necessary. I believe that
>> only controls the downloading of the Android NDK, which you're not
>> interested in using.
>>
>> GN ("generate ninja") and Ninja work together to provide Make-like
>> functionality. Ninja is designed to be simple but fast, GN does all the
>> evaluation of flags and conditions. By inspecting the generated *.ninja
>> files, you can check what GN did with the args you provided.
>> gclient is a dependency management tool (similar to git submodules); it
>> is not involved in the build process itself.
>>
>> On Wed, Sep 19, 2018 at 4:00 AM <gra...@grahamreeves.com> wrote:
>>
>>> I'm trying to build v8 for an arm cpu, and I have gcc/++/etc for that
>>> architecture built on osx (so I can cross compile), which currently builds
>>> my executable, all working fine.
>>>
>>> Now I'm hoping to build v8. Whatever OS side changes I might need to
>>> make, (this is not for linux) I can do.
>>>
>>> What I haven't managed to do yet, is get v8 compiling.
>>> Is this possible with depot_tools/ninja ?
>>>
>>> I've not been able to find any guides so far that aren't android
>>> focussed, eg.
>>>
>>> https://stackoverflow.com/questions/43490689/cross-compiling-v8-build-for-android-on-mac
>>> https://github.com/v8/v8/wiki/Cross-compiling-for-ARM
>>>
>>> From what I can tell, the gclient setup has some specific setup for when
>>> the target_os is "android".
>>> Maybe it's using some explicit NDK based paths to find GCC executables?
>>> (This is a little hidden)
>>> I looked at the gn --args all and couldn't really see anything about
>>> explicitly setting toolchain paths
>>>
>>> Is convention to build as if it's android, and maybe swap out all of
>>> NDK's gcc with my own?
>>> or set the target_os to unix, and then... where would I put the
>>> toolchain?
>>>
>>> I've set *is_clang = false*
>>>
>>> Unless I'm overthinking it? This is my error when I try to build
>>> arm.release. I have been assuming there are no rules setup to build .cc
>>> with a particular gcc executable
>>>
>>> ninja: error: '../../src/base/bits.cc', needed by
>>> 'clang_x86_v8_arm/obj/v8_libbase/bits.o', missing and no known rule to make
>>> it
>>>
>>>
>>> toolchain.ninja (which I assume is like a makefile, I'm very new to
>>> ninja/gclient) has entries for cc
>>>
>>> rule cc
>>>
>>> command = ../../third_party/llvm-build/Release+Asserts/bin/clang -MMD
>>> -MF ${out}.d ${defines} ${include_dirs} ${cflags} ${cflags_c} -c ${in} -o
>>> ${out}
>>>
>>> description = CC ${out}
>>>
>>> depfile = ${out}.d
>>>
>>> deps = gcc
>>> But I guess they're inheritly wrong?
>>>
>>> I feel like I've just missed an obvious step with setting up the target,
>>> but the android setup is obfuscated so I'm blindly hunting around trying to
>>> see if export CC= is set somewhere :)
>>>
>>>
>>> --
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> --
>
> - Graham Reeves
> - http://www.grahamreeves.com/
>
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