CMake and Specified unknown feature "cxx_std_ 17"

CMake
#1

I’m trying to learn CMake and I’m following the console app example. However I’m getting the following error:

CMake Error in CMakeLists.txt:
  Specified unknown feature "cxx_std_	17" for target "TaggerApp".

But I’m setting CMake to use C++ 20.

set(CMAKE_CXX_STANDARD 20)

Using CMake cmake version 3.21.3

Any ideas?

#2

Are you using any custom modules, and do any of those set the C++ standard to 17 in their module metadata blocks? Perhaps there’s an unexpected character in there (a tab, by the looks of things) that the parsing code isn’t handling properly.

#3

That was it, thanks. Is it possible to work around that in juceaide/cmake? Seems to be a pretty big limitation if you can’t use CMake if you save your source with tabs?

#4

Yeah, it’s probably just a regex bug in the parser. I’ll take a look at it tomorrow.

#5

The following fixed it for me, if you don’t want to have to change all the regexps

index 5f5f1de8c..f4b19baa7 100644
--- a/extras/Build/CMake/JUCEModuleSupport.cmake
+++ b/extras/Build/CMake/JUCEModuleSupport.cmake
@@ -119,6 +119,7 @@ function(_juce_extract_metadata_block delim_str file_with_block out_dict)
     set(append NO)
 
     foreach(line IN LISTS module_header_contents)
+        string(REPLACE "\t" " " line "${line}")
         if(NOT append)
             if(line MATCHES " *BEGIN_${delim_str} *")
                 set(append YES)
#6

Thanks for reporting this issue. It should be fixed here:

2 Likes