Support for Microblaze and OpenRISC ?

[tpetazzoni]

Buildroot is building Qt5 for a large number of architectures, and the build now fails on Microblaze and OpenRISC architecture because the copy of the double-conversion library in Qt5 doesn't have support for those architecture.

I am willing to test on those architectures what needs to be tested, but unfortunately the comment at https://github.com/google/double-conversion/blob/master/double-conversion/utils.h#L60 is not clear enough (to me) to know what to test.

Also, wouldn't it make sense for the code in utils.h to assume that DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS is false for unsupported/unknown architectures ?

[floitsch]

I will see if setting the default to false always works.

In the meantime, here is how to test it (from memory):
Create two files and compile them separately:

// div.c
double Div_double(double x, double y) { return x / y; }

// main.c
double Div_double(double x, double y);

int main(int argc, char** argv) {
  return Div_double(89255.0, 1e22) == 89255e-22;
}

Compile them separately and link the o-files.
./main || echo "correct" should now tell you whether the conversion is correct.

If you get "correct" as result, we can just add the new architectures to the "good" list; otherwise to the "bad" list.
If all tests pass, that should be enough.

[tpetazzoni]

Thanks for the quick feedback. I can run the tests, but I only have access to Qemu emulation for those architecctures ? Is it a good enough test or do you need a test on real hardware ?

[floitschG]

Ideally I would test on real hardware, but I assume that the emulator does the right thing. (Otherwise programs wouldn't work).

[pseiderer]

Added double-conversion support for the Qt5 (bundled double-converison library) buildroot cross-compile (aarch64_be [1], or1k [2][3], microblazeel/microblazebe [4]) lately, see the links for the
corresponding architecture defines and (qemu only) Div_double tests...

[1] http://lists.busybox.net/pipermail/buildroot/2018-August/227675.html
[2] http://lists.busybox.net/pipermail/buildroot/2018-August/228151.html
[3] http://lists.busybox.net/pipermail/buildroot/2018-August/228150.html
[4] http://lists.busybox.net/pipermail/buildroot/2018-August/228543.html

[floitsch]

Thanks.
I updated the header.
Note that the file had already changed, and that your (@pseiderer ) patches will now be conflicting.