CMake 3.23.0-rc1 | Exposes illegal generator expression

Development
1

The following generator expression is causing issues in cmake 3.23.0-rc1

    set(foobar TRUE)
    target_link_libraries(my_library PRIVATE
        $<$<OR:$<CONFIG:Debug>,$<BOOL:${foobar}>>:
            advapi32.lib
        >
    )

However, the following works fine:

    set(foobar TRUE)
    target_link_libraries(my_library PRIVATE
        $<$<OR:$<CONFIG:Debug>,$<BOOL:${foobar}>>:advapi32.lib>
    )

EDIT:

Based on everyone’s feedback it appears we just have illegal CMake code which the 3.23 rc1 exposed. The issue is quick enough to fix in our code.

2

To help those who are googling here are the errors I got:

Output from VS2022:

35>LINK : fatal error LNK1104: cannot open file '$<1:.obj'

Output from Ninja:

ninja: error: build.ninja:2422: bad $-escape (literal $ must be written as $$)
3

Did this ever work? The argument splitting happens here before the genex parser, so you’re passing these arguments to target_link_libraries:

  • $<$<OR:$<CONFIG:Debug>,$<BOOL:${foobar}>>:
  • advapi32.lib
  • >

None of these are genexes (the first does contain some, but is the $<1: you see).

1 Like
4

Yes it works fine on 3.22 / 3.21

Here is some example code we currently use. If this syntax is illegal I didn’t realize until now since it’s been working.

5

It’s worth noting that this breakage only occurred with target_link_libraries and target_compile_definitions still works fine for us.

6

I have my doubts that ever did work, at least not in the way you expected. You might find the following article I published recently to be helpful:

If you want to confirm the behavior with different CMake versions, use get_target_property(prop my_library LINK_LIBRARIES) after you call target_link_libraries(). Print the value of ${prop} and if you see semicolons inserted in the middle of what you provided, that confirms that your generator expression is being split instead of being treated as a single whole.

2 Likes
7

Since when did CMake allow any line-breaks or whitespace in general within generator-expressions?
I thought this would never have worked?

Edit: I answered via Email and I wasn’t aware of all the existing answers. Apparently, GMail made multiple, separate Email-threads out of this, not all containing all answers.
Therefore just ignore my question.

8

Is it just me or is the website of your example code not reachable?
(I assume it is a company internal page only?)

9

I accidentally posted an internal link. I updated it to the open source version.

11

This was also reported as CMake Issue 23203. See discussion there for analysis and further updates.

1 Like