Am 14.02.2018 um 20:43 schrieb valdis.kletni...@vt.edu:
Doesn't "make" already do what you want?
No, make itself cannot generate dependency lists on its own, it needs
tooling like gcc -MD ... to do that. I'm interested in a generic
approach. But it my read and thus obey them.
Oh, wait...
dependency recording, because the "results" of running "ls -l" do depend
on its shared libraries!
This way lies madness - touch glibc or other package like that, and you just
forced
a rebuild of the entire world. In fact, I suspect that trying to follow
"dependencies"
to that level will result in build times close to what a 'make world' would do,
because
computing what ends up being the transitive closure of all file references is
painful.
Hint: To really do this correctly, you need to be able to force 100% code path
coverage - otherwise you won't pick up the fact that /usr/lib64/libsnark.so is
only
actually used in an error path or similar rare-access corner case.
Well, unwanted dependencies could be excluded by a blacklist, although I
still believe that at least /_most_/ of the required shared libraries
should rightfully be kept as dependencies, last but not least because
libraries are changed occasionally only on a build server, making world
builds rare as well.
For bonus points:
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_MONETARY", O_RDONLY|O_CLOEXEC)
= -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MONETARY", O_RDONLY|O_CLOEXEC)
= 3
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_TIME", O_RDONLY|O_CLOEXEC) =
-1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_TIME", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_NUMERIC", O_RDONLY|O_CLOEXEC)
= -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_NUMERIC", O_RDONLY|O_CLOEXEC) =
3
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_CTYPE", O_RDONLY|O_CLOEXEC) =
-1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_CTYPE", O_RDONLY|O_CLOEXEC) = 3
Which file(s) count? How do you test for all values of $LANG and the various
LC_*
environment variables?
There's a reason that most sane software builds and tools like rpm / dpkg and
so on just check "glibc is still version 2.22" and don't bother going any
further than that.
And it just gets worse if you include kernel patches - how many modules end up
involved in an open() call on a USB device? How do you detect that your code
"depends" on a given behavior - often kernel patches address error conditions
that doesn't change the perceived behavior in your userspace program...
... until a rare error condition arises. At this point, you need 100% code
coverage
of both the userspace *and* the kernel.
I'm not so sure whether full coverage is really necessary. Instead, the
depencency record of a full succesful initial build might be sufficient.
Even considering other influencing things like the environment should be
possible.
To quote the movie Animal House: "My advice to you is to start drinking
heavily....."
You are most probably right with that, but I'd still like to continue
pondering ... - as long as there is a way to yield the filename of an
opened file using (fast) ftrace instead of slow ptrace?
Thus, I'd still be interested in a solution or hint to my initial question.
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