Make Chromium build

[dmik]

This is a continuation of bitwiseworks/qtwebengine-os2#1 dedicated to building the original Chromium source code.

Note that the build process itself is intended to be started using qmake makefiles from within the qtwebengine repository. But qmake does no more than simply runs gn to generate ninja build files and then runs ninja. I.e. prepares and starts a native Chromium build process. While this process can be then started manually from $(BLDROOT)/qtwebengine/src/core/debug (or release) by calling ninja like this:

cd "$(BLDROOT)"/qtwebengine/src/core && "$(BLDROOT)"/qtwebengine/src/3rdparty/ninja/ninja.exe -v  -C "$(BLDROOT)"/qtwebengine/src/core/$(BUILD_TYPE) QtWebEngineCore

it's still recommended to use qmake makefiles to avoid any de-synchronization with Qt sources.

[dmik]

Then next rather big step is to port the message_pump machinery. I actually already did that when porting Mozilla (check https://github.com/bitwiseworks/mozilla-os2/commits/master/ipc/chromium/src/base and around) but Mozilla uses a very old version of Chromium and a lot has changed since then so some aligning is needed.

[dmik]

The message_pump machinery is mostly done (a commit will follow). Then ext task is thread_local_storage. In old Chromium in Mozilla we used pthread but now I have to do it natively as pthread destructor handling is not perfect (and will not work in some cases). And Chromium performs its own processing anyway.

[dmik]

I'm getting build issues in utf_string_conversions.cc because std::is_integral<wchar_t>::value is false with the new GCC 9.x although it must be true of course. This might require more some more GCC work within bitwiseworks/gcc-os2#16, sigh...

[dmik]

With LIBC and GCC fixed, the string functions build fine now. Next stops besides pthread TLS are these (all expected):

• LaunchProcess (launch_posix.cc), need to use spawn2 instead of fork there.
• UnixDomainSocket (unix_domain_socket.cc, sync_socket_posix.cc, some alignments to features missing on OS/2).
• URandomFD (rand_util_posix.cc)
• Condition and lock variables (condition_variable_posix.cc, lock_impl_posix.cc, might be related to pthread as well).
• Metrics code (histogram.cc, process_metrics.cc)

[dmik]

LaunchProcess requires some tricks to be done. In POSIX, they sometimes want the child to inherit a specific FD of the parent. Sometimes this FD is required to be inherited under a specific file number in the child (i.e. not the original one). All this is achievable (with dup2) but not out of the box. The main problem is thread safety. I fear Chromium starts processes from many threads. So doing it w/o locking might mix things up. Also, inheritance is a big question. On OS/2 all file handles are inherited by default and this is surely not what Chromium wants. In spawn2 inheritance may be completely suppressed with P_2_NOINHERIT flag, but this makes it impossible to inherit specific descriptors. I think that the simplest way to go here is to extend LIBCx spawn2 to allow for selective inheritance of specified file handles.

[dmik]

With the new LIBCx spawn2 update, doing LaunchProcess was quite easy (and much easier than Unix or even Windows code!).

I've also stumbled upon psmedley/gcc#34 when building histogram code:

D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/metrics/histogram.cc:350:34: error: 'round' is not a member of 'std'; did you mean 'round'?
  350 |     next = static_cast<int>(std::round(exp(log_next)));
      |                                  ^~~~~
In file included from C:/usr/include/c++/9/math.h:30,
                 from C:/usr/include/c++/9/cmath:45,
                 from D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/numerics/checked_math_impl.h:12,
                 from D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/numerics/checked_math.h:13,
                 from D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/numerics/safe_math.h:8,
                 from D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/time/time.h:63,
                 from D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/metrics/histogram_base.h:20,
                 from D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/metrics/bucket_ranges.h:30,
                 from D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/metrics/histogram.h:81,
                 from D:/Coding/qt5/qt5/qtwebengine/src/3rdparty/chromium/base/metrics/histogram.cc:10,
                 from gen/base/base_jumbo_12.cc:5:
C:/usr/include/math.h:289:8: note: 'round' declared here
  289 | double round(double);
      |        ^~~~~

It can be worked around the way I did it in QtDeclarative but I guess it's time to fix GCC instead as it should be easy and will free us from working around these bits in other software.

[SilvanScherrer]

bitwiseworks/gcc-os2#15 weil known id say