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Clinton Roy: clintonroy

Tue, 2015-02-03 19:28

Did a few conference things.

Caught up with a dear friend for dinner.

Filed under: diary

Clinton Roy: clintonroy

Tue, 2015-02-03 19:28

Humbug day, with both the lca debrief and the election, double excitement! Unfortunately my partner in crime, Russell, had to attend to an emergency situation and couldn’t stay for the debrief, a large part of the enjoyment I get out of the debrief is disagreeing with Russell. Fortunately Tomas stepped in and added a great deal of information including a number of talks that I never would have bothered looking at, which is after all the entire point of the debriefs.

Filed under: Uncategorized

Jonathan Adamczewski: What’s the difference between 0xffffffff and 0xffffffffu?

Tue, 2015-02-03 09:27

In C++, what is the difference between 0xffffffff and 0xffffffffu?

This one’s pretty easy to answer with this information from the C++ standard:

The type of an integer literal is the first of the corresponding list in Table 6 in which its value can be represented.

0xffffffff is a hexadecimal constant, it’s too big to be represented in a (signed) int, so — by the terms of the standard — the type of 0xffffffff is unsigned int.

Furthermore, each of these hexadecimal literals will have a different type:

0x7fffffff // int 0xffffffff // unsigned int 0x1ffffffff // long int (or long long int) 0x1ffffffffu // unsigned long int (or unsigned long long int)

But to answer the original question, there is no difference between 0xffffffff and 0xffffffffu apart from this:

@twoscomplement One is a commonly used curse when the compiler screws up.

— Colin Riley (@domipheus) January 30, 2015

Stewart Smith: Building OpenPower firmware for use in POWER8 Simulator

Tue, 2015-02-03 09:27

Previously, I blogged on how to Run skiboot (OPAL) on the POWER8 Simulator. If you want to build the full Open Power firmware environment, including the Petitboot bootloader and kernel, you can now do so!

My pull request for an op-build target for the simulator has been merged, so you can now do the following three steps to compile a kernel+initramfs to use with your built skiboot for development purposes:

git clone --recursive cd op-build . op-build-env op-build mambo_defconfig && op-build

Then you wait for a whole bunch of time while everything compiles! Afterwards, you should be left with a zImage.epapr in output/images/ that you can copy into your skiboot directory.

With zImage.epapr in your skiboot directory, when you run “make check”, the skiboot test suite will actually launch the simulator to verify that your skiboot code boots all the way to the petitboot prompt!

We now have two boot tests as part of “make check” for skiboot!