cmake: add directory to be searched for header files - c++

Question

I am writing c++ code to run tests on an arduino project I've written. In order to run it, I need it to include mockups of a couple libraries (the original libraries don't work in c++). The mockups are in my src directory, along with the tests in main.cpp. The files that rely on the mockups are in the parent directory of src, and I cannot modify them to refer to src without breaking their ability to run when uploaded to an arduino. I also cannot add the mockups or main.cpp to the parent directory, as this would interfere with the operation of the arduino code.
So, I need to add the child directory with the mockups to the directories that are searched when compiling the files in the parent directory.
Directory Outline:
parent
forTest.h
forTest.cpp
src
parson.h
parson.c
String.h
String.cpp
main.cpp
CMakeLists.txt
build
In this case, main.cpp has "#include ../forTest.cpp", and forTest.cpp has "#include parson.h" and "#include String.h"
I am currently running the following code in CMakeLists.txt:
cmake_minimum_required (VERSION 2.6)
project(makeTest)
include_directories(../ )
set (makeTest_VERSION_MAJOR 1)
set (makeTest_VERSION_MINOR 0)
add_executable(makeTest main.cpp ../forTest.cpp String.cpp parson.c)
I then build it in the build directory from the command line with
cmake -G "Unix Makefiles" ../src
make
The cmake command resolves successfully, but the make command hits "fatal error: parson.h not found" when building forTest.cpp
How can I resolve this?
edit: my apologies if this has an obvious answer, I'm very new to Cmake
edit the second: using the changes suggested by Gergely Nyiri and changing #include to #include "/usr/include/string.h" resolves several errors, but introduces a new error : "implicit instantiation of undefined template" during the make step.
It refers to the following code in by string.h mockup file:
#ifndef STRING_H
#define STRING_H
#include "/usr/include/string.h"
using namespace std;
class String {
private:
std::string thisString;
char chars[];
...
#endif
which returns the error:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/cstring:61:
/Users/douglas/Desktop/parts/makeHolder/testMake/src/string.h:9:14: error:
implicit instantiation of undefined template 'std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >'
std::string thisString;
This is followed by:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/iosfwd:193:32: note:
template is declared here
class _LIBCPP_TEMPLATE_VIS basic_string;

Answer 1

First of all, I would propose to put CMakeLists.txt in your source root. Then:
cmake_minimum_required (VERSION 2.6)
project(makeTest)
include_directories(src)
set (makeTest_VERSION_MAJOR 1)
set (makeTest_VERSION_MINOR 0)
add_executable(makeTest src/main.cpp forTest.cpp src/String.cpp src/parson.c)
Configure & build:
cd build
cmake ../
make
Even better if you use target_include_directories instead of include_directories:
..
add_executable(makeTest src/main.cpp forTest.cpp src/String.cpp src/parson.c)
target_include_directories(makeTest PRIVATE src)