Working v8 sample to load file in win-x64 or win-x86 #105

wickyhu · 2023-03-28T06:45:52Z

Hi,

I'm looking for a working sample with v8 win-x64 or win-x86 binaries.
I was successful with common binaries to load and render pdf, but always get memory access violation when swiched to v8 binaries.
I searched and found FPDF_InitEmbeddedLibraries in comments, but seems it is not found in v8 dll.
Could you advice me correct initial steps for v8?

Thanks!
Wicky Hu

bblanchon · 2023-03-28T07:08:55Z

Hi @wickyhu,

With the recent builds, you no longer need to call FPDF_InitEmbeddedLibraries().
Instead, I patch FPDF_InitLibraryWithConfig() so that it initializes V8 for you.

I last tested the V8 build some time ago; maybe an upstream change is causing a bug now.
I'll look into this and keep you updated.

Best regards,
Benoit

wickyhu · 2023-03-28T07:35:57Z

Hi Benoit,

Thank you for the quick reply.
I will wait for your good news.

Thanks~
Wicky Hu

bblanchon · 2023-03-28T07:50:32Z

I just ran a test program: it doesn't crash, but some elements are missing, so there is definitely something wrong.
@wickyhu, how did you make it crash?

wickyhu · 2023-03-28T09:25:12Z

Hi, bblanchon,

I have a fork of PdfiumViewer, which I combined some enhancements from others.
It was working properly with NuGet package bblanchon.PDFium.Win32.

I changed the package to bblanchon.PDFium.V8.Win32 just now.
So you can re-produce the issue by below steps:

clone the project: https://github.com/wickyhu/PdfiumViewer.git
compile and start Demo project
open a pdf file.
It would crash at call to FPDFDOC_InitFormFillEnvironment.

I guessed I need to do some initilization for v8 to make it working.
Please have a try.

Thanks~
Wicky Hu

mara004 · 2023-03-28T10:24:45Z

I've been facing similar problems with a crash at FPDFDOC_InitFormFillEnvironment() when using the V8 enabled binaries with pypdfium2 (see pypdfium2-team/pypdfium2#182).
Last time, I assumed that was because we don't implement all mandatory fields of FPDF_FORMFILLINFO, but perhaps this hypothesis was wrong, seeing as the same code can render forms correctly with non-V8 builds.

mara004 · 2023-03-28T10:35:06Z

Instead, I patch FPDF_InitLibraryWithConfig() so that it initializes V8 for you.

I've been using FPDF_InitLibrary(), does the patch cover that as well? Anyway, we still get the same crash even if changing the code to FPDF_InitLibraryWithConfig( FPDF_LIBRARY_CONFIG(2, None, None, 0) ).

bblanchon · 2023-03-28T11:53:11Z

@mara004, my test program calls FPDFDOC_InitFormFillEnvironment() but doesn't crash.
FPDF_InitLibrary() calls FPDF_InitLibraryWithConfig(), so it should work too.

mara004 · 2023-03-28T12:09:56Z

my test program calls FPDFDOC_InitFormFillEnvironment() but doesn't crash.

With pypdfium2, the crash is constantly reproducible:

Patch: enable_forms_with_v8.patch.txt
Install: PDFIUM_USE_V8=1 pip3 install -e .
Test: make test

bblanchon · 2023-03-28T15:23:05Z

I updated the example to call FPDFDOC_InitFormFillEnvironment() and triggered a full build:
https://github.com/bblanchon/pdfium-binaries/actions/runs/4543264945
So far, no crash.

wickyhu · 2023-03-29T06:03:11Z

Hi, bblanchon,

I just tried the example.c in my environment:
win11, vs2022 community

I created an empty C++ console project named test, and build example.c with latest downloaded pdfium-v8-win-x64.tgz.

Below are my steps and findings:

Case 1: form_callbacks.version = 1

run test.exe test.pdf out.pdf
the exe completed without error, however, the out.pdf is corrupted, it can not be opened in acrobat reader or chrome
when I traced into source, I found the returned form is zero for FPDFDOC_InitFormFillEnvironment call
FPDF_FORMHANDLE form = FPDFDOC_InitFormFillEnvironment(doc, &form_callbacks);

Case 2: form_callbacks.version = 2

changed version from 1 to 2 , because of comments from https://pdfium.googlesource.com/pdfium/+/refs/heads/main/public/fpdf_formfill.h line 377
form_callbacks.version = 2;
build and run test.exe test.pdf out.pdf
got exception on call FPDFDOC_InitFormFillEnvironment
Exception thrown at 0x00007FF91A2120AB (pdfium.dll) in Test.exe: 0xC0000005: Access violation reading location 0x0000000000000018.

Best Regards
Wicky Hu

wickyhu · 2023-03-29T06:12:24Z

Hi, bblanchon,

One more information for Case 2:

when I run Case 2 exe in command promt, I don't get error message, just no out.pdf generated
when I run Case 2 in vs2022 debug mode, I got exception catched by vs2022

Best Regards
Wicky Hu

wickyhu · 2023-03-29T06:23:22Z

Hi, bblanchon,

I further tried example.c with pdfium-win-x64.tgz, which is non-v8 version.

Case 1: version=1, no error, returned form of FPDFDOC_InitFormFillEnvironment is not zero, but out.pdf is corrupted
Case 2: version=2, no exception, returned form of FPDFDOC_InitFormFillEnvironment is not zero, but out.pdf is corrupted

Best Regards
Wicky Hu

bblanchon · 2023-03-29T06:28:27Z

Hi Wicky,

Thank you very much for this information; there may be a problem with the initialization of XFA. I'll look into that.

The output from example.c is not a PDF but a PPM, a simple image format.
You can read this file format with GIMP, for example.

Best regards,
Benoit

wickyhu · 2023-03-29T06:42:54Z

Hi bblanchon,

Got it, I can open out.ppm now.

Best Regards
Wicky

bblanchon · 2023-03-29T12:23:37Z

I added a call to cppgc::InitializeProcess(); it seems to have fixed the issue.

wickyhu · 2023-03-29T14:04:01Z

Hi Benoit,

I just re-downloaded the v8 x64 binary from home page, it seems same as previous version.
I guess new build is not yet ready for downloading.
I will test again after new build released.

Thank you very much for the so quick reponse!

Best Regards
Wicky

bblanchon · 2023-03-29T16:16:35Z

You can download the build artifacts here:
https://github.com/bblanchon/pdfium-binaries/actions/runs/4552831557#artifacts

mara004 · 2023-03-29T17:04:48Z

Sounds good, thanks!

See bblanchon/pdfium-binaries#105

mara004 · 2023-03-29T17:30:54Z

Also thanks a lot to @wickyhu for reporting this!
(When I initially noticed the problem, I should probably have asked here in the first place rather than assuming it was an issue with my config.)

bblanchon · 2023-03-29T18:04:33Z

I’m closing this; don’t hesitate to open a new issue.
Thanks a lot guys.

wickyhu · 2023-03-30T01:26:11Z

Hi Benoit,

I just tested example.c with latest binaries.
There seems still an issue, not sure whether it's designed or not.

pdfium-v8-win-x64
case1: version=1, form=0, no error, out.ppm is good <---Note: here form=0, not same as other cases
case2: version=2, form>0, no error, out.ppm is good
pdfium-win-x64
case1: version=1, form>0, no error, out.ppm is good
case2: version=2, form>0, no error, out.ppm is good

The new build works in my project now.
Thanks again!

Best Regards
Wicky

bblanchon · 2023-03-30T07:15:34Z

The comment you referred to previously gives an explanation:

When PDFium is built without the XFA module, version can be 1 or 2.
[...]
When PDFium is built with XFA module then the version must be 2.

To me, this explains why FPDFDOC_InitFormFillEnvironment() returns 0 with the V8 build, since XFA is enabled.

wickyhu · 2023-03-30T07:17:31Z

Yes, you are correct, it's reasonable. Thanks~~

mara004 · 2023-04-04T09:27:32Z

Fix confirmed with yesterday's build. pypdfium2's test suite now runs as expected with the V8 binaries.

mara004 · 2023-05-27T10:22:02Z

Hi @bblanchon,

A pypdfium2 user is asking for XFA support (pypdfium2-team/pypdfium2#221), and we both figured out that FPDF_LoadXFA() always seems to return error despite the V8/XFA enabled binaries.

Is it possible there is still something wrong with XFA init?

Thanks!

bblanchon · 2023-06-05T19:05:25Z

@mara004, I saw your message, and I plan on testing this function soon, but I'm overwhelmed at the moment.
I'll get back to you as soon I can put my hands on it.

mara004 · 2023-06-05T20:10:06Z

Thanks for the response. Take your time. :) I already guessed you might be away or else busy.

mara004 · 2023-06-20T20:32:26Z

FYI, there's been a report on pdfium's mailing list concerning an out-of-memory error on library init with iOS.
From the stack trace, it seems like the V8 enabled binaries. cppgc::InitializeProcess() seems to be the problematic call: https://groups.google.com/g/pdfium/c/XG7hE1K3Ug8

Is it possible this is caused by the pdfium-binaries V8 patch?
Just mentioning for the record as I saw it and thought of this thread. No need to hurry.

bblanchon · 2023-06-21T09:11:02Z

The last message on the thread says:

Problem solved. I was able to run it on my iPad.
I built using "build.sh" from pdfium-binaries. When doing the build, I added the "build for musl" build option.

I'll assume that this was the issue.

mara004 · 2023-06-21T10:00:17Z

Yeah, sounds like it had nothing to do with the V8 patch after all. Sorry for the disruption.

mara004 · 2023-08-11T18:09:52Z

Hi @bblanchon,
I don't want to disturb you - just a small notification this XFA quest still stands, as it was some time ago now.
Thanks!

bblanchon · 2023-08-12T07:42:49Z

Thank you for reaching out. You're right; this issue got out of my attention.
I'll try to work on this during the weekend. Hopefully, today 🤞

mara004 · 2023-08-12T13:22:35Z

Nevermind, when setting chrome://flags/#pdf-xfa-forms to Enabled, Chromium can display our test file correctly, but with our code FPDF_LoadXFA() fails. So we would still be glad if you could take a look.

bblanchon · 2023-08-12T17:22:12Z

I made some discoveries:

FPDF_LoadXFA() must be called after FPDFDOC_InitFormFillEnvironment()
The m_pJsPlatform of the FPDF_FORMFILLINFO passed to FPDFDOC_InitFormFillEnvironment() must point to an IPDF_JSPLATFORM
The version of the IPDF_JSPLATFORM must be set to 3
The callback pointers in IPDF_JSPLATFORM can be null

Something along those lines:

IPDF_JSPLATFORM platform_callbacks = {0};
platform_callbacks.version = 3;

FPDF_FORMFILLINFO form_callbacks = {0};
form_callbacks.version = 2;
form_callbacks.m_pJsPlatform = &platform_callbacks;
FPDFDOC_InitFormFillEnvironment(doc, &form_callbacks);

FPDF_LoadXFA(doc);

When you do this, FPDF_LoadXFA() succeeds 🎉

However, when we call FPDF_DestroyLibrary() after a successful FPDF_LoadXFA(), the following assertion fails:

fxjs/cfxjs_engine.cpp:324: void FXJS_Release(): Assertion `!g_isolate || g_isolate_ref_count == 0' failed.

There is undoubtedly something wrong with my patch to this function, but it's late, so I must stop here for today.

mara004 · 2023-08-12T17:44:06Z

Gotcha, thanks for the pre-requisites checklist, that was an eye-opener.
We had a typo in the FPDF_FORMFILLINFO construction. It's not jsPlatform, but m_pJsPlatform. (I inherited that typo from the reporter's code snippet and didn't verify.) Unfortunately setting a wrong field silently passes.

My sample now renders correctly. I didn't have trouble with crashes on library destruction yet.
Did you make sure to close all objects correctly?

Anyway, thanks a lot!

bblanchon · 2023-09-25T08:11:23Z

I finally found what was causing the assertion failure: you must call FPDFDOC_ExitFormFillEnvironment() before FPDF_CloseDocument().

mara004 · 2023-09-25T16:28:31Z

Yeah I think the API contract with pdfium is that objects should be closed in reverse order to loading.
(I doubt if it's in the headers, but I once asked on the mailing list.)

bblanchon added the bug label Mar 28, 2023

bblanchon added a commit that referenced this issue Mar 28, 2023

Make the example a bit more realistic (#105)

4e1cec2

bblanchon added a commit that referenced this issue Mar 28, 2023

Make the example a bit more realistic (#105)

bed969a

mara004 mentioned this issue Mar 29, 2023

Crash on forms with V8/XFA enabled pdfium binaries pypdfium2-team/pypdfium2#182

Closed

bblanchon added a commit that referenced this issue Mar 29, 2023

V8: call cppgc::InitializeProcess() (issue #105)

d0bdcf8

mara004 added a commit to pypdfium2-team/pypdfium2 that referenced this issue Mar 29, 2023

Update init_forms()

4c3d00f

See bblanchon/pdfium-binaries#105

bblanchon closed this as completed Mar 29, 2023

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mara004 mentioned this issue Aug 12, 2023

Prevent setting non-existent struct fields (ctypesgen issue) pypdfium2-team/pypdfium2#246

Closed

mara004 mentioned this issue Sep 28, 2023

XFA support - which library? #131

Open

ajrcarey mentioned this issue Dec 28, 2023

Segfault when Pdfium compiled with v8/xfa ajrcarey/pdfium-render#130

Closed

bblanchon mentioned this issue Apr 19, 2024

Errors using FPDF_LoadXFA in v8 build #165

Closed

Working v8 sample to load file in win-x64 or win-x86 #105

Working v8 sample to load file in win-x64 or win-x86 #105

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