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bug(cmake): fix cmake install exports (#10)
If you want to access cmake targets of a library, keep the following in
mind. Your library could be either consumed by an `add_subdirectory`
(that's the way CPM and therefore edm works), or it could be consumed by
`find_package` (the standard way for general package managers, yocto,
debian ...).
If your library is consumed by `add_subdirectory`, then the consumer
will see all of your *local* targets, even the ones, that you're not
planning to expose/export (that is also one of the major drawbacks of
`add_subdirectory`). If your library is consumed by `find_package`,
then only the exported targets are visible.
Usually, when you're maintaining a library, you want write it in a way
that it can be consumed in both ways. Meaning, both ways should be
compatible with this usage
```
target_link_library(some_depending_target
PRIVATE
you_lib_namespace::your_lib_target
)
```
For this to work, you need to understand how the name of your library
gets exported.
When your library is consumed by `add_subdirectory`, then everything is
visible. So if you create your library like this:
```
add_library(din)
add_library(cbv2g::din ALIAS din)
```
Your consumer will see both `din` and `cbv2g::din`. Unfortunately,
using `din` here is a bit risky, as this *short* target name might
collide with other library targets (hence, when you want your library
consumable with `add_subdirectory`, you should prefix basically every
target - again, one of the drawbacks of using `add_subdirectory`).
So lets make this compatible by using
```
add_library(cbv2g_din)
add_library(cbv2g::din ALIAS cbv2g_din)
```
You're expecting your consumer to use the alias (`cbv2g::din`).
Now when you want to *install export* your targets, you need to create
an export first and add your targets to it by
```
install(
TARGETS
cbv2g_din
...
EXPORT
cbv2g-targets
)
```
Here, `cbv2g-targets` is the name of the *export*, you want to install.
Furthermore, it is not allowed to use `ALIAS` targets in this command.
Secondly, you need to *install* this export by using
```
install(
EXPORT
cbv2g-targets
NAMESPACE
cbv2g
)
```
This command has a `NAMESPACE` argument and this namespace will get
prepended to the name of the target. But now, the name of the exported
target will be `cbv2g::cbv2g_din`, because it adds the name of real,
*non-aliased* target to the namespace. But we actually want to have
`cbv2g::din` as the exported target name. In order to get this, we
would either have to use `din` as the library target name, instead of
`cbv2g_din` (but yielding the problems with possible collisions) or set
the following property:
```
set_property(TARGET cbv2g_din PROPERTY EXPORT_NAME din)
```
This will basically tell cmake to use a different name than the target
name when creating the export name of this library.
For maximum compatibility, I've chosen to set the `EXPORT_NAME`
property.
Btw, the helper function `evc_setup_package` internally calls
`install(EXPORTS ...)` and forwards the `NAMESPACE` argument.
Signed-off-by: aw <aw@pionix.de>- Loading branch information
