Cmake: read variables from another (processed) directory - scope

I am trying to interrogate the inclusion path of a series of addsubdirectories():
-projectA
-projectB
-projectC
In this setup, projectA is adding ProjectB as a subdirectory which in turn adds ProjectC as a subdirectory. I want to let projectC know about the hierarchy.
I can achieve this by recursive calls
get_directory_property(parent DIRECTORY ${cur_dir} PARENT_DIRECTORY)
which will return nothing when it reaches projectA. That almost does it. It would be nice however, if I could read the ${PROJECT_NAME} from these directories and return A-B-C instead of projectA-projectB-projectC.
So my question is: Is there any way of reading the variables from a directory that is already parsed?
Note that in this case, although projectC would inherit variables from its parent, but the standard cache variables are replaced in the child projects, which is why I can't use them.

you can do:
get_directory_property(output DIRECTORY dir/path DEFINITION PROJECT_NAME)
or any normal variable:
get_directory_property(output DIRECTORY dir/path DEFINITION myVariable)

Related

How do I use one .env as the source of truth

I am creating a build system for development purposes for the FreeCAD application. Repo is here if you want to get a better scope of what I'm talking about.
Essentially the folder structure is:
(Main)
(Linux)
(Ubuntu)
ubuntu.sh
ubuntu.Dockerfile
(Fedora)
fedora.sh
fedora.Dockerfile
(Windows)
(Mac)
.env
What I want to do is use the env variables in .env as a central source of truth for all the build scripts in the tree. But I don't want to have to explicitly define the path of the .env inside the files, absolute or relative paths, as I'm still iterating and I don't want to update all the files if I rearrange the tree. Alternatively, I don't want to put independent .env's in all the child dirs for the same reason (unless they auto update somehow)
My question is as follows:
How do I just explicitly define the "local" path of .env in each script, Dockerfile, etc but only have to modify one top level .env file to auto-update an evolving tree. In a cross platform way
Some things I thought through:
Windows uses "hard links" which are equivalent but non compatible with POSIX hardlinks. I thought about creating windows.env and posix.env in each child dir that point to the same main .env. But most config files can only take one .env path argument.
I thought about writing a script that will update all the .env's when run (would rather not have to), or alternatively, I will accept an answer that uses some dotenv tooling to accomplish the same goal as long as it's cross-platform, and runs locally. I'm just not super familiar with those toolings. I would prefer the tooling or script run as a service and not have to be run everytime in order to update the files.
IF I'm using Git AND only referring to shell scripts, then a command at the top of the script such as . /$(git rev-parse --show-toplevel)/.env works well but has major limitations for use with dockerfiles and other yml based file types.
I currently use a run.sh file at the top level dir that sources the .env and then calls the other files within it. This seems to be the most used pattern I see in other repos. But this means I need to have two files run.sh and run.pwsh which just seems extranuous and hacky to add extras files that are basically one liners.

Flag to Create Missing Directories During fs.promises.writeFile

As I review these file system flags, I'm I correct in concluding that there is no flag you can pass to fs.promises.writeFile that will automatically create all missing directories leading up to a filename? If not, which flag does this?
I don't like solutions that check for the existence of the folders first before attempting writeFile, because after the folders are created that check happens every time you write to a file in that folder.
In my program, after the folders are created once, it should always be there, so it seems more efficient to only create the folders if there is an exception. However, I'm hoping there is a flag that avoids all this micro-management.
If a flag for auto-creating the folders doesn't exist for writeFile, then I'd like to attempt writeFile first, and then (only if there is an exception) create the folders recursively.
fs.promises.writeFile() does not automatically create the directory structure for you. That must exist first.
If you want to automatically create the path because you received an error indicative of a path problem, you can use fs.promises.mkdir() and pass the recursive flag.
And you could, of course, create your own wrapper function that calls fs.promises.writeFile() and if it gets whatever error you get when the path doesn't exist (you'd have to test to see exactly what that error is), then call fs.promises.mkdir() and then repeat the fs.promises.writeFile(). It could all be wrapped in your own utility function.

How does Scons compute the build signature?

I keep different versions of one project in different directories. (This does make sense in this project. Sadly.) As there are only minor differences between the versions, I hope I can speed all builds after the first one by using a common cache directory for all builds.
Unfortunately I had to realise that, when building an object file from the same sources in different directories, SCons 2.3.3 stores the result on different locations in the cache. (The location is equal to the build signature, I assume.) The same sources are recompiled for each and every directory. So why does SCons determine different build signatures although
the compile commands are identical and
the sources and the include files are the same (identical output of of the preprocessor phase, gcc -E ...)
I'm using the decider "MD5-timestamp"
Even the resulting object files are identical!
For a trivial example (helloworld from the SCons documentation) re-using the cache works. Though in the big project I'm working on, it does not. Maybe the "SCons build environment" influences the build signature, even if it does not have any effect on the compile command?
Are there any debug options that could help besides --cache-debug=-? Which method of SCons determines the build signature?
The folders look somewhat like this:
<basedir1>/
SConstruct
src/something.cpp …
include/header.hpp …
<basedir2>/
SConstruct
src/something.cpp …
include/header.hpp …
/SharedCache/
0/ 1/ 2/ … F/
I check out the project in both basedir1 and basedir2 and call scons --build-cache-dir=/SharedCache in both of them. (EDIT: --build-cache-dir is a custom option, implemented in the SConstruct file of this project. It maps to env.CacheDir('/SharedCache').
EDIT2: Before I realized this problem, I did some tests to evaluate the effects of using --cache-implicit or SCons 2.4.0.
This is the code of the method get_cachedir_bsig() from the file src/engine/SCons/Node/FS.py:
def get_cachedir_bsig(self):
"""
Return the signature for a cached file, including
its children.
It adds the path of the cached file to the cache signature,
because multiple targets built by the same action will all
have the same build signature, and we have to differentiate
them somehow.
"""
try:
return self.cachesig
except AttributeError:
pass
# Collect signatures for all children
children = self.children()
sigs = [n.get_cachedir_csig() for n in children]
# Append this node's signature...
sigs.append(self.get_contents_sig())
# ...and it's path
sigs.append(self.get_internal_path())
# Merge this all into a single signature
result = self.cachesig = SCons.Util.MD5collect(sigs)
return result
It shows how the path of the cached file is included into the "cache build signature", which explains the behaviour you see. For the sake of completeness, here is also the code of the get_cachedir_csig() method from the same FS.py file:
def get_cachedir_csig(self):
"""
Fetch a Node's content signature for purposes of computing
another Node's cachesig.
This is a wrapper around the normal get_csig() method that handles
the somewhat obscure case of using CacheDir with the -n option.
Any files that don't exist would normally be "built" by fetching
them from the cache, but the normal get_csig() method will try
to open up the local file, which doesn't exist because the -n
option meant we didn't actually pull the file from cachedir.
But since the file *does* actually exist in the cachedir, we
can use its contents for the csig.
"""
try:
return self.cachedir_csig
except AttributeError:
pass
cachedir, cachefile = self.get_build_env().get_CacheDir().cachepath(self)
if not self.exists() and cachefile and os.path.exists(cachefile):
self.cachedir_csig = SCons.Util.MD5filesignature(cachefile, \
SCons.Node.FS.File.md5_chunksize * 1024)
else:
self.cachedir_csig = self.get_csig()
return self.cachedir_csig
where the cache paths of the children are hashed into the final build signature.
EDIT: The "cache build signature" as computed above, is then used to build the "cache path". Like this, all files/targets can get mapped to a unique "cache path" by which they can get referenced and found in (= retrieved from) the cache. As the comments above explain, the relative path of each file (starting from the top-level folder of your SConstruct) is a part of this "cache path". So, if you have the same source/target (foo.c->foo.obj) in different directories, they will have different "cache paths" and get built independent of each other.
If you truly want to share sources between different projects, note how the CacheDir functionality is more intended for sharing the same sources between different developers, you may want to have a look at the Repository() method. It let's you mount (blend in) another source tree to your current project...

build variable in Linux kernel Makefile

I am currently trying to understand the build process for the Linux kernel. While looking through the Makefiles, I found several rules in the form
scripts_basic:
$(Q)$(MAKE) $(build)=scripts/basic
$(Q)rm -f .tmp_quiet_recordmcount
which all recursively call other make processes and also pass the directory to process. Simultaneously, there seems to be a variable, which is passed, indicating what to do with the subdirectory (the $(build) part.
Looking at the make process, as far as I can see, this always seems to be obj, I cannot find any other value for this variable so far during the make process. Also, I cannot seem to find any place where this variable is set.
So what exactely is this variable for and how is it used (e.g., where is set and processed).
Not exactly. The relevant bit is in scripts/Kbuild.include, where it says
build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
What this means is that if $(KBUILD_SRC) is not empty, the path to scripts/Makefile.build is given as an absolute path (or at least with a path that can be found from the working directory) by prepending the path to the top of the kernel source tree. As far as I can tell, this is to make the sub-makes all use the same Makefile and avoid having the same make code several dozen times.

Adding files to sourcecontrol on linux using cleartool

I have a file that i want to add to sourcecontrol on linux using cleartool .
I've followed the IBM documentation for this, i've tried this:
cleartool mkelem testScript.sh
I got an error: Can't modify directory "." because it is not checked out.
I also would like to know how can i checkout/checkin files or directories and setting activities.
You need to checkout the parent folder first.
cd /path/to/file/
cleartool mkact newfile
cleartool checkout -c "add file" .
cleartool mkelem testScript.sh
cleartool checkin -nc
The cleartool mkact would work if you are in an UCM view.
It will create and set a new activity, which will record the files and folder you will modify.
Here, the new activity newFile will record the new version of the parent folder, as well as the version 0 and 1 of the file.
You should create separate questions for .. separate questions...
Going back to the original - the reason why it isn't working is, as VonC has pointed out, you haven't checked out the parent of the file. Remember, when you run "cleartool mkelem", you are about to modify the contents of the parent directory (. in this case) by adding a new "pointer" to the element you're now creating. As with everything else in clearcase, when you want to modify the contents of an element, you have to check it out first.
One of ClearCase's greatest strength (and hardest to wrap one's head around) is the concept of an "element", IMO. "Everything" behaves similarly with an element. Making any change to an "element" (file or directory) means you have to check it out first to make that change.
In the case of a file, that's easy to grasp - you're just editing lines in a file. For a directory, it's almost as easy - you can think of a directory as just a list of pointers to data blobs. We make the name of the blob something convenient we can remember (like foo.java or myapplication.cc or README.md). But we can also change the name of the pointer (even though it points to the same data blob) by renaming a file. We can remove the pointer to the blob without impacting the blob itself by using "rmname". That's essentially what "rmname" does.
In ClearCases' case, the mkelem command is a little bit special - it creates the initial datablob, and adds a pointer to that datablob in the current directory (kind of does 2 things at once).

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