How to strip trailing whitespace in CMake variable?

Question

We are trying to improve the makefiles produced by CMake. For Clang, GCC and ICC, we want to add -march=native. The block to do so looks like:

#         


        

Answer 1

Adding dollar sign and curly braces, ${UNAME_MACHINE}, results in the same original problem (the newline is still present).

If you use curly braces you also need quote marks. EG:

string(STRIP "${UNAME_MACHINE}" UNAME_MACHINE)

Answer 2

This strips terminating newline in the variable <varname>:

string(REGEX REPLACE "\n$" "" <varname> "${<varname>}")

Works for one of the project I involved to since CMake 2.8.

Answer 3

execute_process has a flag for stripping trailing whitespace on either standard out or standard error (or both)

            [OUTPUT_STRIP_TRAILING_WHITESPACE]
            [ERROR_STRIP_TRAILING_WHITESPACE]

https://cmake.org/cmake/help/v3.0/command/execute_process.html

Answer 4

You can also use CMake's string STRIP command which will remove leading and trailing spaces (and the trailing newline).

string(STRIP <string> <output variable>)