# INTERFACE\_INCLUDE\_DIRECTORIES not transitive for target\_link\_libraries
**URL:** https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028
**Category:** Usage
**Created:** [September 3, 2021, 11:54am UTC](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028 "2021-09-03T11:54:49Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Ronald](https://discourse.cmake.org/u/Ronald)
#### Post date: [September 3, 2021, 11:54am UTC](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028/1 "2021-09-03T11:54:49Z")
# Env
- OS: Linux
- cmake: 3.21.1
# Test Code
```cmake
cmake_minimum_required(VERSION 3.20)
project(test_cmake_transitive_deps LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
macro(dump_target_includes TARGET_NAME)
message("=====================dump_target_includes begin (${TARGET_NAME})=====================")
get_target_property(PROP_TMP
${TARGET_NAME}
INCLUDE_DIRECTORIES)
message(----INCLUDE_DIRECTORIES----)
foreach(PATH_TMP ${PROP_TMP})
message("* " ${PATH_TMP})
endforeach()
get_target_property(PROP_TMP
${TARGET_NAME}
INTERFACE_INCLUDE_DIRECTORIES)
message(----INTERFACE_INCLUDE_DIRECTORIES----)
foreach(PATH_TMP ${PROP_TMP})
message("* " ${PATH_TMP})
endforeach()
message("=====================dump_target_includes end (${TARGET_NAME})=====================")
endmacro()
add_library(a a/a.cpp)
target_include_directories(a PUBLIC a)
dump_target_includes(a)
add_library(b b/b.cpp)
target_link_libraries(b PUBLIC a)
dump_target_includes(b)
```
project file structure
```auto
CMakeLists.txt
a/a.h
a/a.cpp
b/b.h
b/b.cpp
```
# Problem
for
- target\_include\_directories(a PUBLIC a)
- `target_link_libraries(b PUBLIC a)`
`dump_target_includes` for `b` is as below, why no inlucde paths for `b`?
```auto
=====================dump_target_includes begin (b)=====================
----INCLUDE_DIRECTORIES----
* PROP_TMP-NOTFOUND
----INTERFACE_INCLUDE_DIRECTORIES----
* PROP_TMP-NOTFOUND
=====================dump_target_includes end (b)=====================
```
---
### Author:  [@marc.chevrier](https://discourse.cmake.org/u/marc.chevrier)
#### Post date: [September 3, 2021, 12:16pm UTC](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028/2 "2021-09-03T12:16:17Z")
This property is computed at generation time. Requesting it at configuration time will not give you the expected value.
If you need the final information, you have to use [generator expression](https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html)`$` which is evaluated at generation time.
---
### Author:  [@Ronald](https://discourse.cmake.org/u/Ronald)
#### Post date: [September 3, 2021, 12:39pm UTC](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028/4 "2021-09-03T12:39:23Z")
> [@marc.chevrier](#):
>
> This property is computed at generation time. Requesting it at configuration time will not give you the expected value.
>
> If you need the final information, you have to use [generator expression](https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html) `$` which is evaluated at generation time.
What does `generation time` mean?
Does it mean buid time?
How to check `*_INCLUDE_DIRECTORIES` for `b` here?
---
### Author:  [@marc.chevrier](https://discourse.cmake.org/u/marc.chevrier)
#### Post date: [September 3, 2021, 12:55pm UTC](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028/5 "2021-09-03T12:55:46Z")
`generation time` is the step where build system files (Makefiles, ninja or whatever depending on what you specify with option `-G`) are generated by `CMake`.
To manipulate target properties with the right information, use [generator expressions](https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html). See also [file(GENERATE)](https://cmake.org/cmake/help/latest/command/file.html#generate).
---
### Author:  [@Ronald](https://discourse.cmake.org/u/Ronald)
#### Post date: [September 3, 2021, 1:44pm UTC](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028/6 "2021-09-03T13:44:26Z")
> [@marc.chevrier](#):
>
> To manipulate target properties with the right information, use [generator expressions](https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html). See also [file(GENERATE)](https://cmake.org/cmake/help/latest/command/file.html#generate).
```cmake
file(GENERATE OUTPUT test_debug_genex.log
CONTENT $)
```
The code above failed, logs as below
```auto
file Unknown argument to GENERATE subcommand.
```
BTW, does it have to save the output to a file, or anyway to output to stdout/stderr?
---
### Author:  [@marc.chevrier](https://discourse.cmake.org/u/marc.chevrier)
#### Post date: [September 3, 2021, 2:55pm UTC](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028/7 "2021-09-03T14:55:53Z")
Use quotes for `CONTENT`:
```cmake
file(GENERATE OUTPUT test_debug_genex.log
CONTENT "$")
```
---
### Author:  [@Ronald](https://discourse.cmake.org/u/Ronald)
#### Post date: [September 3, 2021, 3:06pm UTC](https://discourse.cmake.org/t/interface-include-directories-not-transitive-for-target-link-libraries/4028/8 "2021-09-03T15:06:08Z")
It works, thanks very much.
BTW space after comma in genex is not allowed.