Sorry, in addition to my above question:
I've started to set up my environment to build v8 (14.0.263.4).
When I run the following command:
local arch=$1
local output_dir=$2
local config=()
# building for Android on a specific arch
config+=('target_os="android"')
config+=("target_cpu=\"$arch\"")
config+=("v8_target_cpu=\"$arch\"")
# release configuration
config+=('is_debug=false')
config+=('symbol_level=0')
config+=('android_unstripped_runtime_outputs=false')
# static library
config+=('is_component_build=false')
config+=('v8_static_library=true')
config+=('v8_monolithic=true')
# use builtin snapshotting
config+=('v8_use_external_startup_data=false')
# disable i18n to reduce size
config+=('v8_enable_i18n_support=false')
# log everything to stdout on Android
config+=('v8_android_log_stdout=true')
# starting from v8 9.9 custom libc compiler causes overlaping issues with
libstdc++.
# we should explicitly disable it
config+=('use_custom_libcxx=false')
tools/dev/v8gen.py -vv -b android.arm.release "$output_dir" -- "${config[@
]}"
It fails with the following message:
/mnt/upstream/v8/buildtools/linux64/gn gen out.gn/arm64-v8a --check
-> returned 1
ERROR at //gni/snapshot_toolchain.gni:115:1: Assertion failed.
assert(v8_snapshot_toolchain != "",
^-----
Do not know how to build a snapshot for
//build/toolchain/android:android_clang_arm on linux arm64
See //BUILD.gn:17:1: whence it was imported.
import("gni/snapshot_toolchain.gni")
^----------------------------------
GN gen failed: 1
And I also get this (before):
Writing """\
android_unstripped_runtime_outputs = false
dcheck_always_on = false
default_min_sdk_version = 21
is_debug = false
target_cpu = "arm"
target_os = "android"
v8_android_log_stdout = true
""" to /mnt/upstream/v8/out.gn/arm64-v8a/args.gn.
It looks like my arguments are being ignored. However, if I go to
*v8/infra/mb/mb_config.pyl
*and I hardcode my flags in the android mixin it works properly.
Is there a bug or am I running something wrong?
Thanks,
Mati.
On Tuesday, September 16, 2025 at 12:53:10 PM UTC-4 Mati Cohen wrote:
> I'm willing to recompile the latest stable version. I am looking at
> build_config.h and for it's using the following implementation:
>
> #if (defined(V8_OS_MACOS) && defined(V8_HOST_ARCH_ARM64)) || \
> (defined(V8_OS_ANDROID) && \
> (defined(V8_HOST_ARCH_ARM64) || defined(V8_HOST_ARCH_X64))) || \
> defined(V8_HOST_ARCH_LOONG64) || defined(V8_HOST_ARCH_MIPS64) || \
> defined(V8_OS_IOS)
> // Android 64 bit has experimental support for 16kB pages.
> // MacOS & iOS on arm64 uses 16kB pages.
> // LOONG64 and MIPS64 also use 16kB pages.
> constexpr int kMinimumOSPageSize = 16 * 1024;
> #elif defined(V8_OS_LINUX) && !defined(V8_OS_ANDROID) && \
> (defined(V8_HOST_ARCH_ARM64) || defined(V8_HOST_ARCH_PPC64))
> // Linux on arm64 (excluding android) and PPC64 can be configured for up
> to 64kB
> // pages.
> constexpr int kMinimumOSPageSize = 64 * 1024;
> #else
> // Everything else uses 4kB pages.
> constexpr int kMinimumOSPageSize = 4 * 1024;
> #endif
>
> Sorry for my ignorance, but does it mean that all Android devices with
> *arm64-v8a* and *x86_64* architectures will use a size of 16KB. Is this
> correct? I am trying to understand if there are devices with *arm64-v8a*
> and *x86_64* architectures which still use 4KB for page sizes.
>
> Thanks,
> Matias.
>
> On Saturday, September 13, 2025 at 7:17:56 AM UTC-4 Ben Noordhuis wrote:
>
>> Assuming recompiling is not a problem for you: just edit
>> build_config.h and change it to 16k.
>>
>> IIRC, stdout and stderr are not normally hooked up to anything on
>> Android but it should be possible to freopen them to a log file.
>>
>> On Fri, Sep 12, 2025 at 4:15 PM 'Matias Cohen' via v8-users
>> <[email protected]> wrote:
>> >
>> > Thanks Ben.
>> >
>> > Yeah, that’s strange. I also noticed that SetDataReadOnly didn’t exist
>> in 10.4.132. Moreover, the V8_FATAL exception that is raised was added even
>> later. Maybe my records about 10.4.132 are wrong, but I am sure that we
>> built v8 last time in August 2022, so I can’t explain it.
>> >
>> > Android Studio don’t show any error message more than the stacktrace I
>> already shared.
>> >
>> > My guess is that kMinimumOSPageSize was still 4KB for Android back then
>> when I built v8 (yet I can’t explain why SetDataReadOnly is part of the
>> stacktrace).
>> >
>> > Is there any way for me to overwrite kMinimumOSPageSize from “outside”
>> v8, just to test if that makes a difference?
>> >
>> > Thanks!
>> >
>> > > On Sep 12, 2025, at 5:20 AM, Ben Noordhuis <[email protected]>
>> wrote:
>> > >
>> > > On Fri, Sep 12, 2025 at 8:26 AM 'Mati Cohen' via v8-users
>> > > <[email protected]> wrote:
>> > >>
>> > >> Hi,
>> > >>
>> > >> My app is using v8 to run a JS environment. Last time I built v8 was
>> about 3 years ago by pointing to 10.4.132.
>> > >>
>> > >> As per Google policy, my app needs to support 16 KB page size and
>> I've been checking all my dependencies to meet that criteria.
>> > >>
>> > >> Apparently, based on my checks, my v8 build does support it and I
>> managed to run the app on my device.
>> > >> However, v8 is crashing as soon as I call V8::Initialize(); with the
>> following stack trace:
>> > >>
>> > >> /base.apk!liben8.so (offset 0x8ad8000) (v8::base::OS::Abort()+28)
>> > >> /base.apk!liben8.so (offset 0x8ad8000) (V8_Fatal(char const*,
>> ...)+376)
>> > >> /base.apk!liben8.so (offset 0x8ad8000)
>> (v8::base::OS::SetDataReadOnly(void*, unsigned long)+52)
>> > >> /base.apk!liben8.so (offset 0x8ad8000)
>> (v8::internal::V8::Initialize()+1552)
>> > >> /base.apk!liben8.so (offset 0x8ad8000) (v8::V8::Initialize(int)+28)
>> > >> /base.apk!liben8.so (offset 0x8ad8000)
>> (Runtime::Runtime(_JNIEnv*)+172)
>> > >>
>> > >> As explained at
>> https://www.google.com/url?q=https://developer.android.com/guide/practices/page-sizes%23check-code&source=gmail-imap&ust=1758273654000000&usg=AOvVaw2eBFhXRa0E0P-iWsikoJCW,
>>
>> I was trying to look for references to PAGE_SIZE and 4096 to see if I was
>> setting up something wrong, but I didn't find anything.
>> > >>
>> > >> Does anyone have any knowledge about this?
>> > >> Thanks a lot,
>> > >> Mati
>> > >
>> > > V8 doesn't use PAGE_SIZE, it uses sysconf(_SC_PAGESIZE).
>> > >
>> > > You mention 10.4.132 but that stack trace is from a different
>> version,
>> > > isn't it? Because SetDataReadOnly didn't exist back then.
>> > >
>> > > It crashes when trying to mprotect(PROT_READ) the command line flags,
>> > > v8_flags. v8_flags is aligned to kMinimumOSPageSize and that _should_
>> > > be 16k on Android but you'll want to double-check that. It's defined
>> > > in src/base/build_config.h.
>> > >
>> > > What error message did V8 print?
>> > >
>> > > --
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