Allow multiple triplets (primary and fallback for eg x64-windows-static-md and x64-windows) in build system integration via find_package

[ankurvdev]

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Is your feature request related to a problem? Please describe.
Allow mix and match 2 triplets (for eg x64-windows-static-md and x64-windows) in a single environment
There's a use case where I need to link with a few ports statically and others dynamically (because they dont support static-linkages)

The problem however is VCPKG doesnt understand multiple triplets .

I can only specify one triplet in VCPKG_TRIPLET to have it look for packages in.

Proposed solution

Allow VCPKG_TRIPLET to be a list. The first is the primary triplet and if a port isnt found in the primary triplet. It can fallback to search the next one in the list.

Describe alternatives you've considered

Current workarounds rely upon manually searching using find_library and find_paths for headers and libs and manually setting up the cmake targets in case we need binaries and packages from the non-primary triplet

Additional context

[Osyotr]

https://github.com/microsoft/vcpkg/blob/c175d8efa7de016dc7a8a22b5c76d201db3ef2d5/docs/users/triplets.md#per-port-customization

Also vcpkg_check_linkage(ONLY_DYNAMIC_LIBRARY) can be used inside a port.

[ankurvdev]

The documentation seems to describe how to create a customized triplet.
I'm not sure if thats entirely relevant to the issue i'm raising.
To clarify here's how one would use vcpkg ports in a project

include(${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake)

OR

set(CMAKE_TOOLCHAIN_FILE "${CMAKE_CURRENT_SOURCE_DIR}/vcpkg/scripts/buildsystems/vcpkg.cmake"
  CACHE STRING "Vcpkg toolchain file")

And by default vcpkg will select a triplet for you

Now if you want to switch to an alternate triplet which is non-default
You'd do something like

set(VCPKG_TARGET_TRIPLET "x64-windows-static-md")
include(${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake)

And after that

find_package(foo) automatically picks up the binaries from x64-windows-static-md triplet

However if you want both

find_package(foo)
find_package(bar)

but we want it to pick up foo:x64-windows-static-md but bar:x64-windows because I want to link dynamically with bar but statically with foo the vcpkg cmake integration doesnt allow for that.

So instead I'm proposing here that instead of VCPKG_TARGET_TRIPLET being a single string, we make it a list so i can specify the preference order
for eg:

set(VCPKG_TARGET_TRIPLET "x64-windows-static-md;x64-windows")
include(${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake)
find_package(foo)
find_package(bar)

and as long as the VCPKG_ROOT contains foo::x64-windows-static-md and not bar::x64-windows-static-md, bar:x64-windows is picked up because the find_package falls back to the second entry in VCPKG_TARGET_TRIPLET

[dg0yt]

bar:x64-windows is picked up because the find_package falls back to the second entry in VCPKG_TARGET_TRIPLET

... until bar:x64-windows-static-md suddenly becomes present, because you installed it by accident, or because it becomes a dependency of another x64-windows-static-md port. This is not reliable. If you want a mixed universe, you must explicitly define this universe - by a customized triplet file.
Not to mention manifest mode.

[ankurvdev]

I agree its not reliable for the general case but there's a huge set of case where there's no dependencies between foo and bar where this could work

Also, I don't think there are alternatives.
I am not aware of how I can create a customized triplet that would let me install both
foo:mytriplet
and
bar:mytriplet
but foo is built statically and bar dynamically.

How would this customized triplet work? Can you please elaborate ?

[dg0yt]

The documentation was linked in the first answer, but again:
https://github.com/microsoft/vcpkg/blob/c175d8efa7de016dc7a8a22b5c76d201db3ef2d5/docs/users/triplets.md#per-port-customization

[ankurvdev]

Ah ok ... Sorry I missed the context earlier, that the triplet file itself contains ports that we want dynamically linked.

Thanks for reposting. I think i understand now.