[cmake] Only set deps for an ExternalProject if the type is executable or library

[lanza]

Summary

cmake fails with an error when attempting to evaluate $<TARGET_FILE:tgt>
where tgt is defined via an add_custom_target and thus the TYPE
is UTILITY. Requesting a TARGET_FILE only works on an EXECUTABLE
or LIBRARY type (e.g. added via add_library or add_executable).

This has always been the case back to at least 3.12 (furthest I checked)
but this is causing a new failure in cmake 3.17 while evaluating
ExternalProjectAdd.

[smeenai]

llvm/cmake/modules/LLVMExternalProjectUtils.cmake

68

Should be STREQUAL instead of SREQUAL on the second one.

68

Nit: it's more common in LLVM to have no space after the if, i.e. if( instead of if (

68

https://cmake.org/cmake/help/latest/prop_tgt/TYPE.html says the library types are "SHARED_LIBRARY", "STATIC_LIBRARY", etc. Does just "LIBRARY" work?

To be fair, I don't know if we even want libraries in this list. But if you wanna fix the CMake issue while having the least chance of changing existing behavior, a blacklist might be easier than a whitelist?

[lanza]

update

llvm/cmake/modules/LLVMExternalProjectUtils.cmake

68

The actual implementation that causes this problem is.

enum TargetType
{
  EXECUTABLE,
  STATIC_LIBRARY,
  SHARED_LIBRARY,
  MODULE_LIBRARY,
  OBJECT_LIBRARY,
  UTILITY,
  GLOBAL_TARGET,
  INTERFACE_LIBRARY,
  UNKNOWN_LIBRARY
};
...
    if (target->GetType() >= cmStateEnums::OBJECT_LIBRARY &&
        target->GetType() != cmStateEnums::UNKNOWN_LIBRARY) {
      ::reportError(context, content->GetOriginalExpression(),
                    "Target \"" + name +
                      "\" is not an executable or library.");
      return nullptr;
    }
...

So I guess I'll just replicate this check.

[lanza]

fix message

[smeenai]

Sure, works for me.

Might be worth adding a comment that this is mirroring logic in CMake, and that CMake 3.17+ error out if you try to use $<TARGET_FILE:...> on an unsupported target.

[lanza]

Closed by https://reviews.llvm.org/rG7f5fe30a150e7e87d3fbe4da4ab0e76ec38b40b9

llvm/cmake/modules/LLVMExternalProjectUtils.cmake

if(NOT ARG_TOOLCHAIN_TOOLS)
     if(NOT _cmake_system_name STREQUAL Darwin)
       # TODO: These tools don't fully support Mach-O format yet.
       list(APPEND ARG_TOOLCHAIN_TOOLS llvm-objcopy llvm-strip)
     endif()
   endif()
   foreach(tool ${ARG_TOOLCHAIN_TOOLS})
     if(TARGET ${tool})
       list(APPEND TOOLCHAIN_TOOLS ${tool})
+
+      # $<TARGET_FILE:tgt> only works on add_executable or add_library targets
+      get_target_property(target_type "${tool}" TYPE)
+      if(NOT target_type STREQUAL "OBJECT_LIBRARY" AND
+         NOT target_type STREQUAL "UTILITY" AND
+         NOT target_type STREQUAL "GLOBAL_TARGET" AND
+         NOT target_type STREQUAL "INTERFACE_LIBRARY")
         list(APPEND TOOLCHAIN_BINS $<TARGET_FILE:${tool}>)
       endif()
+
+    endif()
   endforeach()
 
   if(NOT ARG_RUNTIME_LIBRARIES)
     set(ARG_RUNTIME_LIBRARIES compiler-rt libcxx)
   endif()
   foreach(lib ${ARG_RUNTIME_LIBRARIES})
     if(TARGET ${lib})
       list(APPEND RUNTIME_LIBRARIES ${lib})