[CMake] Controlling order of includes with INTERFACE_INCLUDE_DIRECTORIES for an IMPORTED target

[David Jobet]

Hello,

we embed in our source a copy of an ICC build of LLVM, that we import :

add_library(global_llvm_external STATIC IMPORTED)
set_property(TARGET global_llvm_external APPEND PROPERTY
INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_CURRENT_SOURCE_DIR}/icc/include)
set_property(TARGET global_llvm_external APPEND PROPERTY
IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/icc/lib/libLLVMCore.a)
set_property(TARGET global_llvm_external APPEND PROPERTY
INTERFACE_LINK_LIBRARIES
${CMAKE_CURRENT_SOURCE_DIR}/icc/lib/libLLVMLTO.a ...)

add_library(global_llvm INTERFACE)
target_link_libraries(global_llvm INTERFACE global_llvm_external)
add_library(global::llvm ALIAS global_llvm)

It works fine, until someone decided to install a more recent version
of LLVM in its development env. (which is not ABI compatible)

Somehow, system includes path are looked into first
g++ ... -I/apps/homefs1/USER/work/. -I. -isystem
/spare/local/USER/conda_root/envs/gcc6cxx14/include -isystem
/apps/homefs1/USER/work/.../libllvm/icc/include ...

so, as with include_directories where it's possible to control the
ordering with BEFORE or AFTER, is there a way to tell cmake that when
linking against global::llvm we want the include directories needed by
global::llvm to be prepended (instead of appended) ?

With regards

David
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[Craig Scott]

Post by David Jobet
Hello,
add_library(global_llvm_external STATIC IMPORTED)
set_property(TARGET global_llvm_external APPEND PROPERTY
INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_CURRENT_SOURCE_DIR}/icc/include)
set_property(TARGET global_llvm_external APPEND PROPERTY
IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/icc/lib/libLLVMCore.a)
set_property(TARGET global_llvm_external APPEND PROPERTY
INTERFACE_LINK_LIBRARIES
${CMAKE_CURRENT_SOURCE_DIR}/icc/lib/libLLVMLTO.a ...)
add_library(global_llvm INTERFACE)
target_link_libraries(global_llvm INTERFACE global_llvm_external)
add_library(global::llvm ALIAS global_llvm)
It works fine, until someone decided to install a more recent version
of LLVM in its development env. (which is not ABI compatible)
Somehow, system includes path are looked into first
g++ ... -I/apps/homefs1/USER/work/. -I. -isystem
/spare/local/USER/conda_root/envs/gcc6cxx14/include -isystem
/apps/homefs1/USER/work/.../libllvm/icc/include ...
so, as with include_directories where it's possible to control the
ordering with BEFORE or AFTER, is there a way to tell cmake that when
linking against global::llvm we want the include directories needed by
global::llvm to be prepended (instead of appended) ?

While not directly answering your question, what version of CMake are you
using? There was a change related to this area in the following merge
request that went in for the 3.12 release:

https://gitlab.kitware.com/cmake/cmake/merge_requests/1968

The part that got my attention is the following claim in the description:

An effect of the -isystem flag is to search the directory after

Post by David Jobet
those specified via -I flags.

Which seems at odds with your observations/comments, unless I'm
misunderstanding what you're saying.

[David Jobet]

what version of CMake are you using?

I'm using cmake version 3.10.0.

Which seems at odds with your observations/comments, unless I'm misunderstanding what you're saying.

Well, what's for sure is that the above invocation does not compile,
but if at our root CMakeLists.txt we add
include_directories(/apps/homefs1/USER/work/.../libllvm/icc/include)

so that the invocation is now :

g++ ... -I/apps/homefs1/USER/work/. -I. -isystem
/apps/homefs1/USER/work/.../libllvm/icc/include -isystem
/spare/local/USER/conda_root/envs/gcc6cxx14/include ...

it compiles fine.

Actually, what's odd is that the path that's being added by
set_property(TARGET global_llvm_external APPEND PROPERTY
INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_CURRENT_SOURCE_DIR}/icc/include)

does not materialize with
-I/apps/homefs1/USER/work/.../libllvm/icc/include
but with
-isystem/apps/homefs1/USER/work/.../libllvm/icc/include

So if -isystem are searched last, then if there's a way to tweak
INTERFACE_INCLUDE_DIRECTORIES to use -I instead of -isystem that would
also work.

David

Post by David Jobet
Hello,
add_library(global_llvm_external STATIC IMPORTED)
set_property(TARGET global_llvm_external APPEND PROPERTY
INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_CURRENT_SOURCE_DIR}/icc/include)
set_property(TARGET global_llvm_external APPEND PROPERTY
IMPORTED_LOCATION ${CMAKE_CURRENT_SOURCE_DIR}/icc/lib/libLLVMCore.a)
set_property(TARGET global_llvm_external APPEND PROPERTY
INTERFACE_LINK_LIBRARIES
${CMAKE_CURRENT_SOURCE_DIR}/icc/lib/libLLVMLTO.a ...)
add_library(global_llvm INTERFACE)
target_link_libraries(global_llvm INTERFACE global_llvm_external)
add_library(global::llvm ALIAS global_llvm)
It works fine, until someone decided to install a more recent version
of LLVM in its development env. (which is not ABI compatible)
Somehow, system includes path are looked into first
g++ ... -I/apps/homefs1/USER/work/. -I. -isystem
/spare/local/USER/conda_root/envs/gcc6cxx14/include -isystem
/apps/homefs1/USER/work/.../libllvm/icc/include ...
so, as with include_directories where it's possible to control the
ordering with BEFORE or AFTER, is there a way to tell cmake that when
linking against global::llvm we want the include directories needed by
global::llvm to be prepended (instead of appended) ?

https://gitlab.kitware.com/cmake/cmake/merge_requests/1968

Post by David Jobet
An effect of the -isystem flag is to search the directory after those specified via -I flags.

Which seems at odds with your observations/comments, unless I'm misunderstanding what you're saying.
--
Craig Scott
Melbourne, Australia
https://crascit.com
New book released: Professional CMake: A Practical Guide

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