How to debug v8 snapshot?

[18楼梦想改造家]

Hi, anyone.

I have a little question. When I read the v8 code, I found a file named `out\book\gen\embedded.S|`. there are some code like this:

``` c++
.def Builtins_DeoptimizationEntry_Eager; .scl 2; .type 32; .endef;
  .octa 0x4c110ff22404110ff200000080ec8148,0xff218245c110ff2102454110ff20824
```

at here , octa is `0x4c110ff`... I want to know why it is this value. So I guess if I could debug the process which generate `|embedded.s|`, it will help me understand it.

I found this function( embedded-file-writer.h - Chromium Code Search  )
``` c++

void MaybeWriteEmbeddedFile(const i::EmbeddedData* blob) const {

if (embedded_src_path_ == nullptr) return;

FILE* fp = GetFileDescriptorOrDie(embedded_src_path_);

std::unique_ptr<PlatformEmbeddedFileWriterBase> writer =

NewPlatformEmbeddedFileWriter(target_arch_, target_os_);

writer->SetFile(fp);

WriteFilePrologue(writer.get());

WriteExternalFilenames(writer.get());

WriteDataSection(writer.get(), blob);

WriteCodeSection(writer.get(), blob);

WriteFileEpilogue(writer.get(), blob);

base::Fclose(fp);

}

```

which related to this process?

So how to debug it, is there are a document for it? Thanks!

[Jakob Gruber]

These are bytestreams of the compiled builtins. The --print-builtin-code d8 flag will show you the disassembled version. Hope that helps!

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Jakob Gruber

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[Wenqin Yang]

embeded.S file was generated by a program called mksnapshot, if you're still want to debug it, you could try to build d8 with "ninja -C /your-path -v", and then you will see a command line which start with mksnapshot near the end of the build process. then you could debug mksnapshot with this command line.

Hope it helps you.