std::map::emplace()

[Ahmed Fakhry]

Why is std::map::emplace() is not available?

error: no member named 'emplace' in 'std::__debug::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >'

Is it because we're building with -std=gnu++11? If yes, why aren't we using -std=c++11?

[Peter Kasting]

On Tue, Mar 28, 2017 at 7:45 PM, Ahmed Fakhry <afa...@chromium.org> wrote:

Why is std::map::emplace() is not available?

From https://chromium-cpp.appspot.com/ : "std::map::emplace() is not yet available on all libstdc++ versions we support."

Basically, it's a fixed library bug, but the fixes came after some of the versions we still have to support on certain platforms.

PK 

[Sunny Sachanandani]

Are you building on Linux with the default sysroot? Maybe because of the old version of libstdc++ in the wheezy sysroot? You can try the use_sysroot = false gn flag and see if that changes anything. The default sysroot is being updated from wheezy to jessie but I don't know the current status of that.

On Tue, Mar 28, 2017 at 7:45 PM, Ahmed Fakhry <afa...@chromium.org> wrote:

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[Daniel Cheng]

There's a non-exhaustive list of broken stuff on https://crbug.com/593874

Daniel

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[Peter Kasting]

On Tue, Mar 28, 2017 at 8:15 PM, Sunny Sachanandani <sun...@chromium.org> wrote:

Are you building on Linux with the default sysroot? Maybe because of the old version of libstdc++ in the wheezy sysroot? You can try the use_sysroot = false gn flag and see if that changes anything. The default sysroot is being updated from wheezy to jessie but I don't know the current status of that.

Note: that's https://bugs.chromium.org/p/chromium/issues/detail?id=701894 for people who want to follow along.

PK

[Ahmed Fakhry]

On Tue, Mar 28, 2017 at 8:15 PM Sunny Sachanandani <sun...@chromium.org> wrote:

Are you building on Linux with the default sysroot? Maybe because of the old version of libstdc++ in the wheezy sysroot? You can try the use_sysroot = false gn flag and see if that changes anything. The default sysroot is being updated from wheezy to jessie but I don't know the current status of that.

Yes, I'm building on Linux. I didn't change the gn arg "use_sysroot" so I assume it's using the default value of "true". 

When I tried to set use_sysroot=false, the generated the following error:

ERROR at //chrome/installer/linux/BUILD.gn:297:19: Empty directory path.

      rebase_path(sysroot),

                  ^------

You can't use empty strings as directories. That's just wrong.

See //chrome/installer/linux/BUILD.gn:356:1: whence it was called.

linux_package("stable") {

^------------------------

See //chrome/installer/BUILD.gn:15:7: which caused the file to be included.

      "//chrome/installer/linux",

      ^-------------------------

Also using std::map::emplace() works find when building Chrome OS using simple-chrome. Note that the our trybots don't seem to be using use_sysroot.

[Jan Wilken]

http://crbug.com/701894 got fixed in the meantime, meaning |std::map::emplace| is available now on all platforms. Here is a quick proof of concept: http://crrev.com/2838553002

I suppose we should update https://chromium-cpp.appspot.com/ and drop the corresponding sentence, what do you think?

[Peter Kasting]

On Mon, Apr 24, 2017 at 2:16 AM, Jan Wilken <jdoe...@chromium.org> wrote:

http://crbug.com/701894 got fixed in the meantime, meaning |std::map::emplace| is available now on all platforms. Here is a quick proof of concept: http://crrev.com/2838553002

\o/

I suppose we should update https://chromium-cpp.appspot.com/ and drop the corresponding sentence, what do you think?

Yep.  The files are in your checkout in styleguide/c++/c++11.html ; feel free to send a CL to a relevant OWNER.

PK

[Jeremy Roman]

Woohoo! Please include a code change to use std::map::emplace in the same CL that makes the styleguide change, but sounds like we might be good to go.

 

PK

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[Jan Wilken]

Thanks all, corresponding CL is out: http://crrev.com/2844443002