[CMake] Spaces in conditional output of generator expressions

[Neil Carlson]

I'm attempting to use a generator expression to conditionally add compile
options. No problem if it is a single option, but I can't figure out how to
manage multiple options (in a single command).

For example, this works:
add_compile_options($<$<COMPILE_LANGUAGE:C>-Wall>)

As does this:
add_compile_options(-Wall -Wextra)

But not this:
add_compile_options($<$<COMPILE_LANGUAGE:C>-Wall -Wextra>)

Nor this:
add_compile_options($<$<COMPILE_LANGUAGE:C>"-Wall -Wextra">)

Or any other variation I could think of.  Either the space breaks the
generator expression, or I get a quoted version of the options that the
compiler sees as a single "option" it doesn't understand.

Is there some way of doing this?

PS: I'm trying to avoid using CMAKE_C_FLAGS. My understanding is that
variable is meant for the end user's use.  Am I mistaken about that?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://cmake.org/pipermail/cmake/attachments/20180602/dea6ce9a/attachment.html>