I have a project (a library) that is subdivided into a few directories with code in them. I’d like to to have g++ search for header files in the project’s root directory, so I can avoid different include paths for same header files across multiple source files.
root/ directory has sub-directories
C/, all of which have
.cpp files inside. If some source file in A wanted to include
file.hpp, which was in B, it would have to do it like this:
#include "../B/file.hpp". Same for another source file that was in C. But, if A itself had sub-directories with files that needed
file.hpp, then, it would be inconsistent and would cause errors if I decided to move files (because the include path would be
Also, this would need to work from other projects as well, which reside outside of
root/. I already know that there is an option to manually copy all my header files into a default-search directory, but I’d like to do this the way I described.
Edit: all programs using the library must compile only with
g++ prog.cpp lib.a -o prog. That means permanently setting the include path for g++!
g++ -I /your/source/root /your/source/root/A/code.cpp g++ -I /your/source/root /your/source/root/A/a/code2.cpp
You can use environment variables to change the path g++ looks for header files. From man page:
Some additional environments variables affect the behavior of the
CPATH C_INCLUDE_PATH CPLUS_INCLUDE_PATH OBJC_INCLUDE_PATH
Each variable’s value is a list of directories separated by a special character, much like PATH, in which to look for header
files. The special character, “PATH_SEPARATOR”, is target-dependent and determined at GCC build time. For Microsoft Windows-based targets it
is a semicolon, and for almost all other targets it is a colon.
CPATH specifies a list of directories to be searched as if specified with -I, but after any paths given with -I options on the
command line. This
environment variable is used regardless of which language is being preprocessed.
The remaining environment variables apply only when preprocessing the particular language indicated. Each specifies a
list of directories to be
searched as if specified with -isystem, but after any paths given with -isystem options on the command line.
In all these variables, an empty element instructs the compiler to search its current working directory. Empty elements can
appear at the beginning
or end of a path. For instance, if the value of CPATH is “:/special/include”, that has the same effect as -I.
There are many ways you can change an environment variable. On bash prompt you can do this:
$ export CPATH=/your/source/root $ g++ /your/source/root/A/code.cpp $ g++ /your/source/root/A/a/code2.cpp
You can of course add this in your Makefile etc.
gcc -I/path -L/path
-I /pathpath to include, gcc will find .h files in this path
-L /pathcontains library files,
Headers included with #include <> will be searched in all default directories , but you can also add your own location in the search path with -I command line arg.
I saw your edit you could install your headers in default locations usually
/usr/local/include libdir/gcc/target/version/include /usr/target/include /usr/include
Confirm with compiler docs though.
it’s simple, use the “-B” option to add .h files’ dir to search path.
E.g. g++ -B /header_file.h your.cpp -o bin/your_command