Source code that handles Javascript XHR requests?

[Robert Oschler]

I have the Chromium project set up on my PC using Visual Studio 2017.  Everything compiles and runs fine.  I am looking for the source code location that handles XHR requests made by Javascript code running in a page loaded into the browser.  Does anyone know what project or source file contains that code?

[PhistucK]

Tip - cs.chromium.org is a great way to browser and search the code.

The C++ implementation of XMLHttpRequest pretty much begins here -

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp?q=xmlhttprequest&sq=package:chromium&dr=CSs

☆PhistucK

On Thu, Jul 27, 2017 at 10:36 PM, Robert Oschler <robert....@gmail.com> wrote:

I have the Chromium project set up on my PC using Visual Studio 2017.  Everything compiles and runs fine.  I am looking for the source code location that handles XHR requests made by Javascript code running in a page loaded into the browser.  Does anyone know what project or source file contains that code?

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[Robert Oschler]

Thanks. I set breakpoints on the constructor for the xmlhttprequest class for that file, and many of the more important class methods (sendBytesData(), etc.). I then loaded a page that I know does several XHR requests, confirming the execution of those requests with the DevTools debugger Network window (with the XHR filter on). None of the breakpoints were ever hit.  I have set breakpoints in other parts of the code not related to XHR requests and they were hit, so I know breakpoints are working.

☆PhistucK

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[PhistucK]

The other breakpoints you set - were they in renderer code (anything under renderer/ or under third_party/WebKit)?

If they were not, then you might not be attaching to the right process, renderers are child processes of the browser process.

If they were, then the JavaScript-to-C++ bindings may call things a bit differently. Try setting a breakpoint on the open method, perhaps.

☆PhistucK

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[Robert Oschler]

I set breakpoints in this exact file:

C:\Users\realsensible\Documents\chromium\src\third_party\WebKit\Source\core\xmlhttprequest\XMLHttpRequest.cpp

"open" was one of the methods I had breakpoints on, all 3 overloads.  None of those were hit either.

Do you know the name(s) of the child process that executes the Javascript/V8 code (where I assume the XHR request would actually be handled)?

Also, I have a vague memory of someone telling me that there's a command line flag or setting that will tell Chrome to run as a single process.  If that is true, would you know what that is?  That would be helpful if this is indeed a process hunting issue.

Am Freitag, 28. Juli 2017 13:19:11 UTC-4 schrieb PhistucK:

The other breakpoints you set - were they in renderer code (anything under renderer/ or under third_party/WebKit)?

If they were not, then you might not be attaching to the right process, renderers are child processes of the browser process.

If they were, then the JavaScript-to-C++ bindings may call things a bit differently. Try setting a breakpoint on the open method, perhaps.

<snip>

[PhistucK]

I do not know the names, I never debugged Chrom(ium). :):

The flag is --single-process, however, it is not guaranteed to work. It breaks a lot, as far as I remember.

https://www.chromium.org/developers/how-tos/debugging-on-windows should be helpful.

☆PhistucK

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