# Using the same namespace for multiple independant projects
**URL:** https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669
**Category:** Usage
**Created:** [August 3, 2023, 8:45am UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669 "2023-08-03T08:45:12Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@olivierbichler-cea](https://discourse.cmake.org/u/olivierbichler-cea)
#### Post date: [August 3, 2023, 8:45am UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/1 "2023-08-03T08:45:12Z")
Hi,
Is there a way to use the same namespace accross multiple packages, like:
```auto
find_package(prog_extA)
find_package(prog_extB)
target_link_librairies(target PUBLIC prog::extA prog::extB)
```
Or even, register multiple packages in the same “meta”-package, like:
```auto
find_package(prog)
target_link_librairies(target PUBLIC prog::extA prog::extB)
```
But without the use of the component mechanism, which would require that all extensions are handled in the same CMake project. My goal is to be able to build sub-packages in fully independant CMake projects. And from my understanding, it is not possible with the component mechanism(?)
Thanks.
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [August 3, 2023, 4:50pm UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/2 "2023-08-03T16:50:01Z")
There’s no rule about namespaces having to match the package name in general, so `prog_extA` and `prog_extB` can both use `NAMESPACE prog::` just fine.
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [August 3, 2023, 4:50pm UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/3 "2023-08-03T16:50:25Z")
And Qt does the second part as well (using `COMPONENTS` to look for the “extensions”).
---
### Author:  [@adaldev](https://discourse.cmake.org/u/adaldev)
#### Post date: [September 3, 2024, 10:28am UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/4 "2024-09-03T10:28:01Z")
AFAIU configuration file creation, when I’m creating `extA` in a namespace `prog`, I will in fact create some `progConfig.cmake`, `progTargets.cmake` and `progTargets-.cmake` files. Thus when I will create `extB` I will overwrite these files and only `prog::extB` will be visible?
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [July 21, 2025, 12:28am UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/5 "2025-07-21T00:28:32Z")
The namespace is independent of the filename; they don’t have to match.
---
### Author:  [@adaldev](https://discourse.cmake.org/u/adaldev)
#### Post date: [July 23, 2025, 7:32am UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/6 "2025-07-23T07:32:15Z")
Hi,
I don’t get it.
According to documentation:
**Config mode**
In this mode, CMake searches for a file called `-config.cmake` or `Config.cmake`. It will also look for `-config-version.cmake` or `ConfigVersion.cmake` if version details were specified (see [Config Mode Version Selection](https://cmake.org/cmake/help/latest/command/find_package.html#version-selection) for an explanation of how these separate version files are used).
Thus as said in a previous comment, adding `prog::extB` will require to create `prog-config.cmake` (for instance).
In my use case, all configurations files will be in a single directory acting as a package repository.
But even if I’d use different directories, `find_package` will stop at the first `prog` configuration file found?
Regards,
A.
---
### Author:  [@vito.gamberini](https://discourse.cmake.org/u/vito.gamberini)
#### Post date: [July 23, 2025, 1:08pm UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/7 "2025-07-23T13:08:26Z")
> [@adaldev](#):
>
> Thus as said in a previous comment, adding `prog::extB` will require to create `prog-config.cmake` (for instance).
This is where your misunderstanding is coming from. A target named `prog::extB` can come from any arbitrary config file. It can come from a file named `SillyLongPackageNameConfig.cmake`. There is no correlation between package name and target name.
CMake doesn’t “actually” have namespaces, it’s merely a convention. The “namespace” is a string prefix, it has no significant semantic meaning to CMake.
---
### Author:  [@adaldev](https://discourse.cmake.org/u/adaldev)
#### Post date: [July 23, 2025, 1:34pm UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/8 "2025-07-23T13:34:34Z")
Hi,
OK but how then does `find_package` proceeds in config mode to find the correct configuration file.
I always believe (perhaps wrongly) that `find_package( COMPONENTS )` was looking for a “target” package::component inside `packageConfig.cmake`?
What I get from your comment is that `package` and namespace are not related?
with the example in my previous comment, I could make a package `progextA` ( **or any other unique name** ) referencing `prog::extA` and another `progextB` referencing `prog::extB`?
If so, Ben Boeckel comments are making sense now. But I think that actual OP’s use-case would be to be able to find all components of the namespace `prog` with a single `find_package`, even if these components come from different projects.
Using his example:
```cmake
# importing all components of the namespace prog
find_package(prog)
# linking some of them
target_link_librairies(target PUBLIC prog::extA prog::extB)
```
For instance, let say I want to add an algorithm to an existing (set of) library(ies), how could I do without modifying the original library project ? To be even more specific. If I want to add something to opencv, how can I do that without editing opencv cmake codes and rebuilding it (or at least regenerating the configuration files)?
Regards,
A.
---
### Author:  [@vito.gamberini](https://discourse.cmake.org/u/vito.gamberini)
#### Post date: [July 23, 2025, 1:46pm UTC](https://discourse.cmake.org/t/using-the-same-namespace-for-multiple-independant-projects/8669/9 "2025-07-23T13:46:23Z")
> [@adaldev](#):
>
> I always believe (perhaps wrongly) that `find_package( COMPONENTS )` was looking for a “target” package::component inside `packageConfig.cmake`?
Components are meaningless to CMake, they are a hint provided to code written by humans. Ie, the handwritten `FindPython` find-module uses components to figure out if you’re asking for the Python interpreter, the Python development libraries, or both. They have no meaning beyond what the developer of a find module or package choose to give to them, CMake does not automatically generate anything directly related to the `COMPONENTS` field of `find_package()`.
> [@adaldev](#):
>
> What I get from your comment is that `package` and namespace are not related?
Correct.
> [@adaldev](#):
>
> But I think that actual OP’s use-case would be to be able to find all components of the namespace `prog` with a single `find_package`, even if these components come from different projects.
Create a `progConfig.cmake` file that calls `find_dependency()` for all the sub packages that you wish to be a part of the meta-package. There is no way to ask “find all the packages that use the string “`prog::*`” in their target names”. You will have to, as a human, know what set of packages you are concerned with when making the meta package.
As Ben mentioned, it’s traditional to use the `COMPONENTS` field when creating such a package to know which packages you’re actually interested in. So the author of the `progConfig.cmake` could write code to check the components list, and only call `find_dependency()` for packages which map to requested items in the list.