Undefined reference to v8::platform::NewDefaultPlatform

[Bogdan Padalko]

Hi!

I'm trying to adapt changes from https://github.com/v8/v8/commit/ffee558e14e28fc8b1f9a3c10ea3615e0d686c7b to replace CreateDefaultPlatform with NewDefaultPlatform calls, however, for some reason I'm getting

/home/vagrant/php-v8/scripts/test_v8/hello_world.cpp:21: undefined reference to `v8::platform::NewDefaultPlatform(int, v8::platform::IdleTaskSupport, v8::platform::InProcessStackDumping, std::unique_ptr<v8::TracingController, std::default_delete<v8::TracingController> >)'

error with the following code:

#include <v8.h>
#include <libplatform/libplatform.h>

#include <stdlib.h>
#include <string.h>

using namespace v8;

void weak_callback(const v8::WeakCallbackInfo<v8::Persistent<v8::String>>& data) {
  printf("Weak callback called\n");
  data.GetParameter()->Reset();
}

int main(int argc, char* argv[]) {
  // Initialize V8.
  v8::V8::InitializeICU();
//  v8::Platform *platform = v8::platform::CreateDefaultPlatform();
//  v8::V8::InitializePlatform(platform);

  std::unique_ptr<v8::Platform> platform = v8::platform::NewDefaultPlatform();
  v8::V8::InitializePlatform(platform.get());

  V8::Initialize();

  v8::Isolate::CreateParams create_params;
  create_params.array_buffer_allocator = v8::ArrayBuffer::Allocator::NewDefaultAllocator();

  // Create a new Isolate and make it the current one.
  Isolate* isolate = v8::Isolate::New(create_params);

  v8::Persistent<v8::String> test;

  {
    Isolate::Scope isolate_scope(isolate);

    // Create a stack-allocated handle scope.
    HandleScope handle_scope(isolate);

    // Create a new context.
    Local<Context> context = Context::New(isolate);

    // Enter the context for compiling and running the hello world script.
    Context::Scope context_scope(context);


    test.Reset(isolate, String::NewFromUtf8(isolate, "Hello' + ', World!'"));
    test.SetWeak(&test, weak_callback, v8::WeakCallbackType::kParameter);


    // Create a string containing the JavaScript source code.
    Local<String> source = String::NewFromUtf8(isolate, "(2+2*2) + ' ' + 'Hello' + ', World!'");

    // Compile the source code.
    Local<Script> script = Script::Compile(source);

    // Run the script to get the result.
    Local<Value> result = script->Run();

    // Convert the result to an UTF8 string and print it.
    String::Utf8Value utf8(isolate, result);
    printf("%s\n", *utf8);
  }

  isolate->LowMemoryNotification();


  // Dispose the isolate and tear down V8.
  isolate->Dispose();
  V8::Dispose();
  V8::ShutdownPlatform();

  return 0;
}

build script:

#!/bin/bash

ROOT=/opt/libv8-6.5
LIB_DIR=$ROOT/lib/

SRC_DIR=$ROOT
INCLUDE_DIR=$ROOT/include

set -x

g++ -std=c++14 hello_world.cpp -o hello_world \
 -g \
 -O2 \
 -std=c++11 \
 -I$INCLUDE_DIR \
 -L$LIB_DIR \
 -Wl,-rpath,$LIB_DIR \
 -lv8_libbase \
 -lv8_libplatform \
 -lv8 \
 -lpthread

I use v8 build with the following params:

gn gen out.gn/x64.release --args="is_debug=false is_component_build=true v8_use_external_startup_data=false"
ninja -v d8 -C out.gn/x64.release

Host is x64 Ubuntu 16.04, libv8 installed from my pinepain/libv8-6.5 PPA (https://launchpad.net/~pinepain/+archive/ubuntu/libv8-6.5)

I'd really appreciate if anybody give it a look and provide some suggestions as after spending two days with this I think I just missing something very simple and obvious.

Regards,
Bogdan

[Ben Noordhuis]

It sounds like a link order issue. What happens when you put `-o
hello_world` last?

[Bogdan Padalko]

Thanks for quick reply! Unfortunately, it's the same. I ended up with hello world example after to trying out to use NewDefaultPlatform with php-v8 (https://github.com/pinepain/php-v8/blob/53a562e10c23e5f835b2ccdb20967f9c4aef529e/src/php_v8_a.cc#L34), which yield me there

/home/vagrant/.phpbrew/php/7.2-debug/bin/php: symbol lookup error: /home/vagrant/php-v8/modules/v8.so: undefined symbol: _ZN2v88platform18NewDefaultPlatformEiNS0_15IdleTaskSupportENS0_21InProcessStackDumpingESt10unique_ptrINS_17TracingControllerESt14default_deleteIS4_EE

With CreateDefaultPlatform it works just fine, and there was no other changes to sources except of using v8 6.5.116 and using NewDefaultPlatform. Bare 6.5.116 with CreateDefaultPlatform works fine.

[Zac Hansen]

If you look at the symbols in your libs is it in there anywhere?

[Bogdan Padalko]

Hi Zac, thanks for the quick reply!

Here's what I see in library:

$ objdump -T /opt/libv8-6.5/lib/libv8_libplatform.so  | grep NewDefault
000000000000a850 g    DF .text    000000000000012e  Base        _ZN2v88platform18NewDefaultPlatformEiNS0_15IdleTaskSupportENS0_21InProcessStackDumpingENSt3__110unique_ptrINS_17TracingControllerENS3_14default_deleteIS5_EEEE

and this is the error I get later when get php-v8 compiled and try to load:

_ZN2v88platform18NewDefaultPlatformEiNS0_15IdleTaskSupportENS0_21InProcessStackDumpingESt10unique_ptrINS_17TracingControllerESt14default_deleteIS4_EE

As you see, they differs and it looks like I missed something, but couldn't grasp what and it looks like this is the cause of

/home/vagrant/php-v8/scripts/test_v8/hello_world.cpp:21: undefined reference to `v8::platform::NewDefaultPlatform(int, v8::platform::IdleTaskSupport, v8::platform::InProcessStackDumping, std::unique_ptr<v8::TracingController, std::default_delete<v8::TracingController> >)'

error too.

Happy New Year!
Bogdan

[Ben Noordhuis]

On Mon, Jan 1, 2018 at 3:00 PM, Bogdan Padalko <zaq17...@gmail.com> wrote:
> Hi Zac, thanks for the quick reply!
>
> Here's what I see in library:
>
> $ objdump -T /opt/libv8-6.5/lib/libv8_libplatform.so | grep NewDefault
> 000000000000a850 g DF .text 000000000000012e Base
> _ZN2v88platform18NewDefaultPlatformEiNS0_15IdleTaskSupportENS0_21InProcessStackDumpingENSt3__110unique_ptrINS_17TracingControllerENS3_14default_deleteIS5_EEEE
>
>
> and this is the error I get later when get php-v8 compiled and try to load:
>
> _ZN2v88platform18NewDefaultPlatformEiNS0_15IdleTaskSupportENS0_21InProcessStackDumpingESt10unique_ptrINS_17TracingControllerESt14default_deleteIS4_EE
>
> As you see, they differs and it looks like I missed something, but couldn't
> grasp what and it looks like this is the cause of
>
> /home/vagrant/php-v8/scripts/test_v8/hello_world.cpp:21: undefined reference
> to `v8::platform::NewDefaultPlatform(int, v8::platform::IdleTaskSupport,
> v8::platform::InProcessStackDumping, std::unique_ptr<v8::TracingController,
> std::default_delete<v8::TracingController> >)'
>
> error too.
>
> Happy New Year!
> Bogdan

If you run them through c++filt, you'll see the difference:

v8::platform::NewDefaultPlatform(int, v8::platform::IdleTaskSupport,
v8::platform::InProcessStackDumping,

std::__1::unique_ptr<v8::TracingController,
std::__1::default_delete<v8::TracingController> >)

vs:

v8::platform::NewDefaultPlatform(int, v8::platform::IdleTaskSupport,
v8::platform::InProcessStackDumping,
std::unique_ptr<v8::TracingController,
std::default_delete<v8::TracingController> >)

I'm guessing one is compiled against different headers than the other
or with a different -std=... flag. If you built V8 with the bundled
clang, try rebuilding it with clang=0.

[Bogdan Padalko]

Thanks Ben! This is it. It was my fault building with clang and hoping that the build will be relocatable.

Building with GN args:

     is_debug: false,
     is_official_build: true,
     is_component_build: true,
     is_cfi: false,
     is_clang: false,
     v8_use_external_startup_data: false,
     treat_warnings_as_errors: false,
     use_custom_libcxx: false,
     use_sysroot: false,
     use_gold: false

works perfect!

Thank you all who's been helping me with this! Happy New Year!

Regards,
Bogdan

[Zac Hansen]

It's not a "relocation" issue, I'm pretty sure -- it's a stdlib issue.   It looks like the first symbol was from libc++ (the __1 gives it away) and the second was most likely from libstdc++.  <== just a guess but pretty consistent with stuff I've seen before.

[Bogdan Padalko]

Indeed. By "relocation" I mean that it was built using one stdlib and moved to the system with another one, but I agree that it's more correct to name as stdlib issue rather then relocation issue. I tried to link with libc++.so that generated by v8 build, though, no luck with it for some reason. For now using is_clang=false works fine, apart that it increases php-v8 tests run time with valgrind enabled significantly.

[Zac Hansen]

The problem is that when you *compile* with libstdc++ when building against the v8 external API header, it generates object files looking for symbols with the libstdc++ names.   

At that point there's no winning because you have v8 libs which need libc++ and your object files which need libstdc++.

At least that's how I understand it.

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[Jean Pix]

BRENDAN EICH suggests the source code compiler be V8 C++ SYNTAX SCRIPT