Query headers added to cmake project - cmake

Question

I would like to get all headers added to cmake project. The use case is that I'd get this list of headers and call some custom validation on them. I would really love this to be a query mechanism to mitigate errors in oversight.
I am not interested in globbing the file system as headers may exist that are not appropriate for every platform. It's also bad.
This is what I would like the usage to look like.
add_library(example_lib
foo.h
foo.cpp
bar.h
bar.cpp
)
add_executable(example main_example.cpp)
target_link_libraries(example example_lib)
# this is the feature I am interested in
get_target_headers(example_header example)
# alternatively
get_target_headers(example_header example example_lib)
do_custom_thing("${example_header}")
A more manual way of doing this would be something like the below. I'd just reuse the example_header variable to do the custom validation.
set(example_header
foo.h
bar.h
)
set(example_source
foo.cpp
bar.cpp
)
add_library(example_lib
${example_header}
${example_source}
)
add_executable(example main_example.cpp)
target_link_libraries(example example_lib)
do_custom_thing("${example_header}")
This is what I'm doing now and it works, I am just wondering if there is a better way.

Answer 1

If all your headers have a ".h" suffix, you could use something like:
function(get_target_headers Headers MainTarget)
# Gather list of MainTarget's dependencies
get_target_property(Dependencies ${MainTarget} LINK_LIBRARIES)
set(AllTargets ${MainTarget})
foreach(Dependency ${Dependencies})
# If this is a CMake target, add it to the list
if(TARGET ${Dependency})
list(APPEND AllTargets ${Dependency})
endif()
endforeach()
# Gather each target's list of source files ending in ".h"
foreach(Target ${AllTargets})
get_target_property(Sources ${Target} SOURCES)
foreach(Source ${Sources})
string(REGEX MATCH "^.*\\.h$" Header ${Source})
if(Header)
list(APPEND AllHeaders ${Header})
endif()
endforeach()
endforeach()
# Since functions have their own scope, set the list in the parent scope
set(${Headers} ${AllHeaders} PARENT_SCOPE)
endfunction()
and invoke it using your first choice:
get_target_headers(example_header example)