Thanks for raising this issue. Sorry to be pedantic, but are you sure your bisect is on that patch? It feels strange that enum classes would have caused this. Can you try reverting that patch and debugging again?

That's what I did. Weird, right?

Just compiled and installed gdb 7.12. Still a problem.

If I set gdb_index to false (which is default) in gn args, the problem goes away. But then I get slow content_shell startup times instead.

I found out what's going on: The symbol lookup machinery in gdb doesn't seem to be able to distinguish between the EDisplay::InlineBox enum (which was introduced by the blamed CL) value and the InlineBox class (in Source/core/layout/line/InlineBox.h). So whenever we use gdb anywhere near the InlineBox class, it goes through all the compilation units that have EDisplay defined (that's more than 2500 files). Or something like that. I don't really know much about the inner workings of gdb, but running the "set debug symtab-create 1" command before running into trouble seemed to suggest something to that effect going on.

Whether this is a bug in gdb or in clang, I do not know. But we can work around the problem by using some other name than InlineBox in EDisplay. In this particular case, that even makes quite a lot of sense, since InlineBox and Box are non-standard property values for an outdated flexbox spec. Before the spec went CR, the values were renamed to "flex" and "inline-flex", rather than "box" and "inline-box". So I'll just go ahead and rename them.

That said, I wouldn't be surprised if there be similar name clashes elsewhere. So ideally this should be fixed. If you know whom to contact in your team who works on things like the clang compiler bundled with the chromium sources, maybe you could Cc them.

I'll file a CL shortly.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/40d77a4fb4d16dec83ecd5be8c98633ac15b6021

commit 40d77a4fb4d16dec83ecd5be8c98633ac15b6021
Author: mstensho <mstensho@opera.com>
Date: Thu Nov 24 14:42:46 2016

EDisplay enum class: Rename [Inline]Box to Webkit[Inline]Box.

The "box" and "inline-box" values (or rather: "-webkit-box" and
"-webkit-inline-box") for "display" are for an early-stage version of the
flexbox spec, which the web embraced before the flexbox spec got around to
going CR (which uses the values "flex" and "inline-flex" instead).

Furthermore: Having both EDisplay::InlineBox enum value and the InlineBox class
(in Source/core/layout/line/InlineBox.h) confuses the symbol lookup in gdb,
which causes a ~40 seconds freeze [1] when working on something that involves the
InlineBox class.

[1] For component builds with gdb_index set to true in gn

BUG= 655961 

Review-Url: https://codereview.chromium.org/2524903003
Cr-Commit-Position: refs/heads/master@{#434316}

[modify] https://crrev.com/40d77a4fb4d16dec83ecd5be8c98633ac15b6021/third_party/WebKit/Source/core/css/CSSPrimitiveValueMappings.h
[modify] https://crrev.com/40d77a4fb4d16dec83ecd5be8c98633ac15b6021/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
[modify] https://crrev.com/40d77a4fb4d16dec83ecd5be8c98633ac15b6021/third_party/WebKit/Source/core/layout/LayoutObject.cpp
[modify] https://crrev.com/40d77a4fb4d16dec83ecd5be8c98633ac15b6021/third_party/WebKit/Source/core/layout/LayoutObject.h
[modify] https://crrev.com/40d77a4fb4d16dec83ecd5be8c98633ac15b6021/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
[modify] https://crrev.com/40d77a4fb4d16dec83ecd5be8c98633ac15b6021/third_party/WebKit/Source/core/style/ComputedStyle.h
[modify] https://crrev.com/40d77a4fb4d16dec83ecd5be8c98633ac15b6021/third_party/WebKit/Source/core/style/ComputedStyleConstants.h

Before we close this, could you please file a bug against GDB for this? :) There is some great context here that they could use to try and fix this bug.

We should really investigate switching to LLDB... :)

Nvm, I'll do this :) Thanks mstensho!

I filed a bug with upstream gdb.
[I couldn't find an existing one there.]
https://sourceware.org/bugzilla/show_bug.cgi?id=21027