Bug 64981 – export JSContextGetBacktrace as SPI in JSContextRefPrivate.h

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Sommer Panage]

UIAutomation for iOS would like to support a Javascript backtrace in our error logs. Currently, the C API does not provide the tools to do this. However, the private API does expose the necessary functionality to get a backtrace (via Interpreter::retrieveLastCaller). We recognize this information may result in failure in the cases of programs run by 'veal', stack frames beneath host function call frames, and in programs run from other programs. Thus, we propose exporting our JSContextGetBacktrace in JSContextRefPrivate.h. This will provide us with the tools we need while not advertising an API that isn't really ready for full use.

[Sommer Panage]

The patch will be added to this bug report shortly.

[Sommer Panage]

Created attachment 101648 [details]
path to export JSContextGetBacktrace functionality as private SPI

[Sommer Panage]

Patch attached.

[Alexey Proskuryakov]

This patch is not marked for review. Did you want it to be reviewed?

Please see <http://www.webkit.org/coding/contributing.html> for information about contributing code to WebKit.

[Oliver Hunt]

Comment on attachment 101648 [details]
path to export JSContextGetBacktrace functionality as private SPI

We're working on a better mechanism for getting a stacktrace.  Once that's in place any API of this kind will be able to use that.

[Sommer Panage]

Yes, I apologize as, we do want the patch reviewed. 

We recognize that there is work underway to get a stack trace into the API. Of course, once that's in place, we would be able to utilize it for our purposes. However, at this point, it is our understanding that this work is in progress and may not be available for some time. As we very much need a solution now, we were hoping to get this in place as, at least, a temporary fix until better methods are made available.

[Oliver Hunt]

Comment on attachment 101648 [details]
path to export JSContextGetBacktrace functionality as private SPI

We'll migrate to the better implementation in future

[WebKit Review Bot]

Comment on attachment 101648 [details]
path to export JSContextGetBacktrace functionality as private SPI

Rejecting attachment 101648 [details] from commit-queue.

Failed to run "['./Tools/Scripts/webkit-patch', '--status-host=queues.webkit.org', '--bot-id=ec2-cq-02', '--port..." exit_code: 2

Last 500 characters of output:
Parsed 4 diffs from patch file(s).
patching file Source/JavaScriptCore/ChangeLog-PEP
Hunk #1 FAILED at 1.
1 out of 1 hunk FAILED -- saving rejects to file Source/JavaScriptCore/ChangeLog-PEP.rej
patching file Source/JavaScriptCore/JavaScriptCore.exp
patching file Source/JavaScriptCore/API/JSContextRef.cpp
patching file Source/JavaScriptCore/API/JSContextRefPrivate.h

Failed to run "[u'/mnt/git/webkit-commit-queue/Tools/Scripts/svn-apply', u'--reviewer', u'Oliver Hunt', u'--force']" exit_code: 1

Full output: http://queues.webkit.org/results/9232141

[Geoffrey Garen]

Comment on attachment 101648 [details]
path to export JSContextGetBacktrace functionality as private SPI

r- because this patch doesn't apply cleanly.

> +++ Source/JavaScriptCore/ChangeLog-PEP	(working copy)

To apply cleanly, you need to patch JavaScriptCore/ChangeLog. (There is no ChangeLog-PEP.)

> failure in the cases of programs run by 'veal'

veal! ;)

[Geoffrey Garen]

One more comment:

> JSContextGetBacktrace

Since this function allocates a string the the caller must release, it should be called "JSContextCreateBacktrace", not "JSContextGetBacktrace". (Same naming conventions as CF.)

[Sommer Panage]

Created attachment 101773 [details]
same backtrace patch with changes suggested by Geoffrey Garen integrated

[WebKit Review Bot]

Comment on attachment 101773 [details]
same backtrace patch with changes suggested by Geoffrey Garen integrated

Rejecting attachment 101773 [details] from review queue.

[e-mail] does not have reviewer permissions according to http://trac.webkit.org/browser/trunk/Tools/Scripts/webkitpy/common/config/committers.py.

- If you do not have reviewer rights please read http://webkit.org/coding/contributing.html for instructions on how to use bugzilla flags.

- If you have reviewer rights please correct the error in Tools/Scripts/webkitpy/common/config/committers.py by adding yourself to the file (no review needed).  The commit-queue restarts itself every 2 hours.  After restart the commit-queue will correctly respect your reviewer rights.

[WebKit Review Bot]

Comment on attachment 101773 [details]
same backtrace patch with changes suggested by Geoffrey Garen integrated

Rejecting attachment 101773 [details] from commit-queue.

Failed to run "['./Tools/Scripts/webkit-patch', '--status-host=queues.webkit.org', '--bot-id=ec2-cq-02', '--port..." exit_code: 2

Last 500 characters of output:
47ac38bc1954a95bbb76e9cf2258dfa2fd0f625d
r91611 = 788227ec3d4f823dac8b3804ad12ab188a0f557e
Done rebuilding .git/svn/refs/remotes/origin/master/.rev_map.268f45cc-cd09-0410-ab3c-d52691b4dbfc
First, rewinding head to replay your work on top of it...
Fast-forwarded master to refs/remotes/origin/master.
Updating chromium port dependencies using gclient...

________ running '/usr/bin/python gyp_webkit' in '/mnt/git/webkit-commit-queue/Source/WebKit/chromium'
Updating webkit projects from gyp files...

Full output: http://queues.webkit.org/results/9230224

[Sommer Panage]

Created attachment 101780 [details]
same backtrace patch with tabs removed from ChangeLog

Some tabs seem to have snuck into the change log. Trying again.

[Gyuyoung Kim]

Comment on attachment 101780 [details]
same backtrace patch with tabs removed from ChangeLog

Attachment 101780 [details] did not pass efl-ews (efl):
Output: http://queues.webkit.org/results/9233218

[Oliver Hunt]

Comment on attachment 101780 [details]
same backtrace patch with tabs removed from ChangeLog

View in context: https://bugs.webkit.org/attachment.cgi?id=101780&action=review

> Source/JavaScriptCore/API/JSContextRef.cpp:211
> +        char levelStr[6];
> +        sprintf(levelStr, "#%d ", count);

should be snprintf if anything i guess, but...

> Source/JavaScriptCore/API/JSContextRef.cpp:226
> +        builder.append(levelStr);

Can you not just use UString::number() here instead?

[Sommer Panage]

I most certainly can use UString::number() -- submitting the change.

[Sommer Panage]

Created attachment 101796 [details]
Same patch, getting rid of sprintf for cleaner UString::number() use instead

[WebKit Review Bot]

Comment on attachment 101796 [details]
Same patch, getting rid of sprintf for cleaner UString::number() use instead

Clearing flags on attachment: 101796

Committed r91627: <http://trac.webkit.org/changeset/91627>

[Eric Seidel (no email)]

Looks landed.  If that's incorrect, please open a new bug per additional patch you'd like to land.