I've worked with many such systems, from the venerable make/autotools system, to Cmake, to Scons, to Ant, Maven, Gradle (Boo!) and who knows what else. I hate them all. They are all misbegotten monstrosities that only their mothers could love.
But like all build systems, Cmake works just great - until it doesn't. In this case:
- It started out by offering an inscrutable error message: "A required package was not found". I'm not making this up, that is the message. Which package? Why so coy, CMake? Cantcha just say???
- So you look in the error log, and you see that a check for Pthreads failed. But you know your system has pthreads, so you flail around for a while, then notice it failed because the test command specified not "-lpthread", but "-lpthreads". Whaa? A bug in CMake? An hour and a half later you finally realize that was a spurious report - the error message was not caused by Pthreads testing but by the check that occurred just before the error message. You proceed to feel both very stupid, because you should have thought of that immediately, and very, very pissed that the morons in charge of Cmake could have saved you the trouble by simply saying what the problem is. I dunno, maybe something like "A required package was not found: gio-unix-2.0>=2.40"? Izzat so hard?
- And the way you actually figure out that gio-unix-2.0 was the problem is by creating a test project and painstakingly going through the CMakeLists.txt file line by line, trial-and-error. You begin to fear you might have an aneurism. You are glad the Cmake devs are not within throttling distance, lest you squeeze their throats very hard.
- But, but, bu bu - my system does so have gio-unix-2.0! It's right there! (Of course, you waste a good 20-30 minutes googling around trying to figure out what exactly gio-unix is).
- More trial and error. Maybe its the version number. You try a bunch, nothing makes a difference, the test always fails.
- Finally, you inspect the pkg-config file for gio-unix-2.0. Everything looks hunky dory. Except for that @[email protected] thingie there, it looks a little fishy, but you are not a pkg-config expert, you assume that it must be there for a reason. But then you look at the related gio-2.0 file, and there in the version field is an actual number! 2.48.1, to be exact!
- So finally it dawns on you: the person whose neck you need to squeeze, hard, mercilessly, is the person who install the broken pkg-config file for gio-unix-2.0, the one that didn't get the version number so it fails all checks.
- But the CMake devs do not get away so easily! It's still a flaw in their product - when they test for a library with a version >=2.40, and the version they get is obviously broken - not a version number at all - they should throw a "broken config file" exception, not a "package not found" error. It's just false to say the package was not found! And it would also be false to say that the package found had too low a version number! It did not fail the version test, it was incapable of even taking the version test, and that is the exception.
The real problem with build systems is that they do not treat the build engineering problem as a software development problem. To manage builds you need a real programming language, and you need to write your build scripts with all the care you would use in writing critical C code. There is actually one project out there that takes this approach, the only one I know of: http://boot-clj.com/. Whereas previous build systems are of the "build a better mousetrap" variety, so they're all pretty much the same thing, boot represents a fairly radical re-conceptualization of what building software is all about.
opkgBoth the Intel Edison and the Dell 3290 (Intel IoT Gateway) with Wind River Linux, being embedded systems, run a Yocto-based OS. The package manager for Yocto is opkg, not apt nor rpm nor any of the other PMs one typically encounters in full-featured Linux environments. Unfortunately, good information on how to correctly use opkg is not easy to find. Here's what worked for me:
Here "Edison" means an Intel Edison module updated to the latest image as of June 2016, and "Gateway" means a Dell/Wyse 3290 running Wind River Linux version 6. Note that the Intel IoT Gateway platform also supports Ubuntu and Windows OSs.
opkg homepage: https://wiki.openwrt.org/doc/techref/opkg.
- Gateway: /etc/opkg/opgk.conf
Here's what I used on the Gateway:
dest root /
dest ram /tmp
lists_dir ext /var/opkg-lists
option overlay_root /overlay
src/gz x86_base http://downloads.openwrt.org/snapshots/trunk/x86/64/packages/base/
src/gz x86_packages http://downloads.openwrt.org/snapshots/trunk/x86/64/packages/packages/
Post a Comment