Hi Jakob,
I did a minimal repo, but I can't reproduce the issue (using v8's clang-cl
compiler to compile it).
I can't spend more time on it right now; we will be sticking to 10.9 for now. I
might do further investigations at a later time.
Thanks for your input.
Regards,
Jean-Claude
On Thu, Aug 10, 2023, at 8:09 AM, Jakob Gruber wrote:
> Interesting.. Sorry, I don't have any more suggestions either. Depending on
> how much time you still have to spend on this, please consider either filing
> a bug at crbug.com/v8/new to document your current findings, or trying to
> build a minimal repro (without V8). I'd still like to understand if this is a
> bug in V8 or in the MSVC stdlib.
>
> On Wed, Aug 9, 2023 at 6:05 PM Jean-Claude Monnin <jc_mon...@emailplus.org>
> wrote:
>> __
>> Hi Jakob,
>>
>> Sorry, I should have looked at the code more carefully before sending my
>> reply. The lambda capture-by-copy of the variadic template arguments being
>> buggy would be one explanation, but it looks like it's something else.
>>
>> I tried following workaround:
>> CodeRange* CodeRange::EnsureProcessWideCodeRange(
>> v8::PageAllocator* page_allocator, size_t requested_size) {
>> base::CallOnce(&init_code_range_once, [&]() {
>> InitProcessWideCodeRange(page_allocator, requested_size);
>> });
>> return process_wide_code_range_;
>> }
>> This uses the overload taking the `std::function<void()>` directly. It
>> crashes in `CallOnceImpl` at call of `init_func()`.
>> I also tried to call `CallOnceImpl` directly, same crash.
>>
>> It looks like the `std::function` is corrupted in `CallOnceImpl`. It works
>> when supplying a static function with no arguments, but any lambda crashes.
>> Using simpler test code, it seems that it's linked to pass a `std::function`
>> across dll boundary. It works when calling an template/inline function, but
>> calling a function exported by the dll doesn't work (see [1]).
>> I can't see why passing a `std::function` to a dll call is problematic. I
>> tested the same test code on another project that uses MSVC compiler and it
>> works fine there. It's not impossible it's a clang issue. Unfortunately,
>> this looks too complicated for me to look further into (I'm not familiar
>> with assembler and such low level stuff).
>>
>> I tried this ugly workaround since I can pass static functions, which allows
>> the compile to pass. d8.exe launches, but tests fail.
>> v8::PageAllocator* g_page_allocator;
>> size_t g_requested_size;
>>
>> static void InitProcessWideCodeRangeNoArgs() {
>> InitProcessWideCodeRange(g_page_allocator, g_requested_size);
>> }
>>
>> // static
>> CodeRange* CodeRange::EnsureProcessWideCodeRange(
>> v8::PageAllocator* page_allocator, size_t requested_size) {
>> static base::Mutex mx;
>> base::MutexGuard guard(&mx);
>> g_page_allocator = page_allocator;
>> g_requested_size = requested_size;
>> base::CallOnce(&init_code_range_once, InitProcessWideCodeRangeNoArgs);
>> return process_wide_code_range_;
>> }
>>
>> Regards,
>> Jean-Claude
>>
>> -------------------
>> [1] Test to reproduce the issue of passing a std::function across dll
>> boundaries:
>>
>> src/base/once.h
>> inline void Test1(std::function<void()> init_func) {
>> printf("Test1 before init_func\n");
>> init_func();
>> printf("Test1 after init_func\n");
>> }
>>
>> V8_BASE_EXPORT void Test2(std::function<void()> init_func);
>>
>> src/base/once.cc
>> void Test2(std::function<void()> init_func) {
>> printf("Test2 before init_func\n");
>> init_func();
>> printf("Test2 after init_func\n");
>> }
>>
>> mksnapshot.cc
>> void TestFunction() {
>> printf(" called TestFunction\n");
>> }
>>
>> int main(int argc, char** argv) {
>> v8::base::Test1([]() {
>> printf(" called CallOnceFake1 lambda\n");
>> });
>>
>> v8::base::Test2(TestFunction);
>>
>> v8::base::Test2([]() {
>> printf(" called CallOnceFake2 lambda\n");
>> });
>>
>> The output is
>>> Test1 before init_func
>>> called CallOnceFake1 lambda
>>> Test1 after init_func
>>> Test2 before init_func
>>> called TestFunction
>>> Test2 after init_func
>>> Test2 before init_func
>> The call to `Test2` with a lambda crashes
>>
>> On Wed, Aug 9, 2023, at 10:32 AM, Jakob Gruber wrote:
>>>
>>>
>>> On Wed, Aug 9, 2023 at 10:05 AM Jean-Claude Monnin
>>> <jc_mon...@emailplus.org> wrote:
>>>> __
>>>> I've tried to figure out a bit more what is going on by adding prints
>>>> along the call stack. It looks like it's the `base::CallOnce` in
>>>> `code-range.cc` introduced in commit 26bc8bb4 that is the problem. Here
>>>> the code with the added prints:
>>>> V8_DECLARE_ONCE(init_code_range_once);
>>>> void InitProcessWideCodeRange(v8::PageAllocator* page_allocator,
>>>> size_t requested_size) {
>>>> i::PrintF(stdout, "InitProcessWideCodeRange %u\n", requested_size);
>>>> CodeRange* code_range = new CodeRange();
>>>> if (!code_range->InitReservation(page_allocator, requested_size)) {
>>>> V8::FatalProcessOutOfMemory(
>>>> nullptr, "Failed to reserve virtual memory for CodeRange");
>>>> }
>>>> process_wide_code_range_ = code_range;
>>>> #ifdef V8_EXTERNAL_CODE_SPACE
>>>> #ifdef V8_COMPRESS_POINTERS_IN_SHARED_CAGE
>>>> ExternalCodeCompressionScheme::InitBase(
>>>> ExternalCodeCompressionScheme::PrepareCageBaseAddress(
>>>> code_range->base()));
>>>> #endif // V8_COMPRESS_POINTERS_IN_SHARED_CAGE
>>>> #endif // V8_EXTERNAL_CODE_SPACE
>>>> }
>>>> } // namespace
>>>>
>>>> // static
>>>> CodeRange* CodeRange::EnsureProcessWideCodeRange(
>>>> v8::PageAllocator* page_allocator, size_t requested_size) {
>>>> i::PrintF(stdout, "CodeRange::EnsureProcessWideCodeRange %u\n",
>>>> requested_size);
>>>> base::CallOnce(&init_code_range_once, InitProcessWideCodeRange,
>>>> page_allocator, requested_size);
>>>> return process_wide_code_range_;
>>>> }
>>>>
>>>> It outputs:
>>>> CodeRange::EnsureProcessWideCodeRange 536870912
>>>> InitProcessWideCodeRange 2034756544 <tel:(203)%20475-6544>
>>>>
>>>> It looks like the `requested_size` isn't forwarded correctly in
>>>> `base::CallOnce`.
>>>> I'm not sure to understand the CallOnce implementation, but I wonder if
>>>> calling `std::function<void()>` with `init_func(args...)` isn't undefined
>>>> behavior. Not sure how to fix/work around.
>>>
>>> Which part would be undefined behavior? From a quick glance, the CallOnce
>>> implementation
>>> <https://source.chromium.org/chromium/chromium/src/+/refs/heads/main:v8/src/base/once.h;l=101;drc=a9163a67bbe920dfcfa6286bf0d172a1af377dba>
>>> looks reasonable to me. It sounds like something around the lambda
>>> capture-by-copy is buggy (accessing the wrong stack slot?). Perhaps you can
>>> verify with disassembly of InitProcessWideCodeRange, or step through and
>>> find out what it's actually copying.
>>>
>>>>
>>>>
>>>> On Wed, Aug 9, 2023, at 8:03 AM, Jakob Gruber wrote:
>>>>>
>>>>>
>>>>> On Tue, Aug 8, 2023 at 3:20 PM Jean-Claude Monnin
>>>>> <jc_mon...@emailplus.org> wrote:
>>>>>> __
>>>>>> Hi Jakob,
>>>>>>
>>>>>> Thanks for your reply.
>>>>>> It looks like using Microsoft's C++ library instead of libc++ is
>>>>>> somewhat exotic for v8. Unfortunately there are cases where it's almost
>>>>>> impossible to switch to libc++.
>>>>>>
>>>>>> Since I have a chance to get some feedback here of how to address this
>>>>>> issue, I'm going to try to give you as much info as possible.
>>>>>>
>>>>>> `mksnapshot.exe` aborts at `VirtualMemoryCage::InitReservation` at
>>>>>> following check:
>>>>>> CHECK(IsAligned(params.reservation_size, allocate_page_size));
>>>>>>
>>>>>> When adding following print on the line before
>>>>>> i::PrintF(stdout, "VirtualMemoryCage::InitReservation %u %u\n",
>>>>>> params.reservation_size, allocate_page_size);
>>>>>> it prints
>>>>>> VirtualMemoryCage::InitReservation 3356617664 65536
>>>>>> It looks like the supplied `params.reservation_size` is not aligned.
>>>>>
>>>>> Thanks for the investigation, very helpful. I wonder where that
>>>>> reservation_size comes from. It doesn't look like any value we'd set in
>>>>> V8. Corrupted? Uninitialized?
>>>>>
>>>>> I'd expect it to be set by mksnapshot here
>>>>> <https://source.chromium.org/chromium/chromium/src/+/refs/heads/main:v8/src/snapshot/mksnapshot.cc;l=282;drc=a9163a67bbe920dfcfa6286bf0d172a1af377dba>
>>>>> and picked up by isolate initialization here
>>>>> <https://source.chromium.org/chromium/chromium/src/+/refs/heads/main:v8/src/heap/heap.cc;l=5420;drc=a9163a67bbe920dfcfa6286bf0d172a1af377dba>.
>>>>> There it should either be some reasonable aligned value, or 0 and we'd
>>>>> fall back to kMaximalCodeRangeSize.
>>>>>
>>>>>>
>>>>>>
>>>>>> Full call stack is included in screenshot below (sorry for the
>>>>>> screenshot, I couldn't find a way to copy text from WinDbg)
>>>>>>
>>>>>> I'm happy to investigate further, but wanted to send this out in case
>>>>>> there is anything specific that would be helpful.
>>>>>>
>>>>>> Jean-Claude
>>>>>>
>>>>>> On Tue, Aug 8, 2023, at 12:13 PM, Jakob Gruber wrote:
>>>>>>> Hi Jean-Claude,
>>>>>>>
>>>>>>> no, we don't have a lot of test coverage for `use_custom_libcxx=false`,
>>>>>>> this mode is only supported on a best-effort basis.
>>>>>>>
>>>>>>> For debugging: a backtrace and symbols would be useful. Does running
>>>>>>> `mksnapshot` in a debugger give more infos? Also, a bisect to find the
>>>>>>> culprit change would be very helpful.
>>>>>>>
>>>>>>> On Thu, Aug 3, 2023 at 6:54 PM Jean-Claude Monnin
>>>>>>> <jc_mon...@emailplus.org> wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> On windows, the v8 version 11.5 build fails when generating the
>>>>>>>> snapshot with following error:
>>>>>>>>
>>>>>>>> C:/Users/jean-claude/Documents/src/google/depot_tools/bootstrap-2@3_8_10_chromium_26_bin/python3/bin/python3.exe
>>>>>>>> ../../tools/run.py ./mksnapshot --turbo_instruction_scheduling
>>>>>>>> --target_os=win --target_arch=x64 --embedded_src gen/embedded.S
>>>>>>>> --embedded_variant Default --random-seed 314159265 --startup_blob
>>>>>>>> snapshot_blob.bin --no-native-code-counters
>>>>>>>> Return code is 2147483651 <tel:(214)%20748-3651>
>>>>>>>>
>>>>>>>> These are the options used (args.gn):
>>>>>>>> is_official_build = true
>>>>>>>> target_cpu = "x64"
>>>>>>>> is_component_build = true
>>>>>>>> use_custom_libcxx = false
>>>>>>>> chrome_pgo_phase = false
>>>>>>>> treat_warnings_as_errors = false
>>>>>>>> fatal_linker_warnings = false
>>>>>>>> symbol_level = 0
>>>>>>>>
>>>>>>>> When using `is_debug=false` instead of `is_official_build = true` it
>>>>>>>> builds fine, but it comes with performance regressions compared to
>>>>>>>> older version 9.3 build with `is_official_build = true`.
>>>>>>>>
>>>>>>>> If using either `is_component_build = false` or `use_custom_libcxx =
>>>>>>>> true`, it builds fine too, however it's not really an option as I need
>>>>>>>> a dll build and I need to use Microsoft's C++ standard library because
>>>>>>>> third party dependencies prevents us to use libc++.
>>>>>>>>
>>>>>>>> I also tried version 11.4 and 11.6 and they give the same error.
>>>>>>>>
>>>>>>>> Any hints in how to diagnose/fix that would be appreciated.
>>>>>>>>
>>>>>>>> Auxiliary question: Is any big project using `use_custom_libcxx =
>>>>>>>> false` (eg. Microsoft's C++ standard library), or is this untested?
>>>>>>>> Chrome/node/deno all use libc++?
>>>>>>>>
>>>>>>>> Best regards,
>>>>>>>> Jean-Claude
>>>>>>>>
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