Environment variables and --warn-uninitialized

Code
1

Environment variables can be used in if command:

if ($ENV{FOO})
message(STATUS “bar”)
endif ()

This works as expected but produces a warning if cmake is executed with --warn-uninitialized and if FOO is not defined. Using DEFINED produces a syntax error because $ENV{FOO} is evaluated to nothing:

if (DEFINED ENV{FOO} AND $ENV{FOO})
message(STATUS “bar”)
endif ()

Adding quotes makes the example work as expected but a warning about uninitialized variable is produced because $ENV{FOO} is evaluated before the if command even receives the arguments:

if (DEFINED ENV{FOO} AND “$ENV{FOO}”)
message(STATUS “bar”)
endif ()

This works as expected and doesn’t produce a warning about uninitialized variable:

if (DEFINED ENV{FOO})
if ($ENV{FOO})
message(STATUS “bar”)
endif ()
endif ()

But is there a way to use an environment variable in a single if command without producing warning about uninitialized variable?

2

No because in CMake, contrary to C or C++, both conditions of an AND are always evaluated.