[flang] Fix issue of flang/runtime/config.h not being found in out of tree builds

[isuruf]

Summary

Fixes https://bugs.llvm.org/show_bug.cgi?id=46078

[PeteSteinfeld]

Thanks for working on this!

I tried your change in my out-of-tree build, and it didn't fix anything. When I do out-of-tree builds, I create a build directory in the flang directory and then call cmake using the following script:

#!/bin/bash
cmake -G Ninja \
  -DCMAKE_CXX_STANDARD=17 \
  -DLLVM_TARGETS_TO_BUILD=host \
  -DLLVM_LIT_ARGS=-v \
  -D LLVM_EXTERNAL_LIT=/mnt/c/GitHub/master/clean/build/bin/llvm-lit \
  -D LLVM_DIR=/mnt/c/GitHub/master/clean/install/lib/cmake/llvm \
  -D MLIR_DIR=/mnt/c/GitHub/master/clean/install/lib/cmake/mlir \
  -DCMAKE_BUILD_TYPE=Release ..

How do you do out-of-tree builds to make this work for you?

[tskeith]

In D81266#2076748, @PeteSteinfeld wrote:

Thanks for working on this!

I tried your change in my out-of-tree build, and it didn't fix anything. When I do out-of-tree builds, I create a build directory in the flang directory and then call cmake using the following script:

#!/bin/bash
cmake -G Ninja \
  -DCMAKE_CXX_STANDARD=17 \
  -DLLVM_TARGETS_TO_BUILD=host \
  -DLLVM_LIT_ARGS=-v \
  -D LLVM_EXTERNAL_LIT=/mnt/c/GitHub/master/clean/build/bin/llvm-lit \
  -D LLVM_DIR=/mnt/c/GitHub/master/clean/install/lib/cmake/llvm \
  -D MLIR_DIR=/mnt/c/GitHub/master/clean/install/lib/cmake/mlir \
  -DCMAKE_BUILD_TYPE=Release ..

How do you do out-of-tree builds to make this work for you?

I'm seeing the same thing as Pete. CMAKE_CURRENT_BINARY_DIR is the right place to look for config.h and I see that it is added to the INCLUDE_DIRECTORIES property of FortranRuntime, but it's not getting added as a -I option to the compilation command.

[isuruf]

Use include_directories instead of target_include_directories

[isuruf]

I was doing a CMake in-tree build of a out-of-llvm-tree flang. I can reproduce with a CMake out-of-tree build of a out-of-llvm-tree flang and fixed it here.

[tskeith]

Looks good now. Thanks for taking care of this.

[PeteSteinfeld]

Looks good to me, too!

Thanks again for doing this.

[tskeith]

@isuruf - OK to merge this?

[isuruf]

Yes, please. Shall I merge this? I don't know what the protocol is in merging.

[DavidTruby]

@isuruf I think you've done enough reviews on here that you should just get direct access yourself.
The protocol is to get commit access as described on this page: https://llvm.org/docs/DeveloperPolicy.html#obtaining-commit-access
Then once a review is approved you can just directly commit the code to master.

[isuruf]

I already have merge access, but haven't merged any flang commits till now. It's in now.

flang/runtime/CMakeLists.txt

check_cxx_source_compiles(
   "
   HAVE_DECL_STRERROR_S)
 
 if (NOT (HAVE_STRERROR OR HAVE_STRERROR_R OR HAVE_DECL_STRERROR_S))
   message(FATAL_ERROR "None of strerror, strerror_r, strerror_s found.")
 endif()
 
 configure_file(config.h.cmake config.h)
+# include_directories is used here instead of target_include_directories
+# because add_flang_library creates multiple objects (STATIC/SHARED, OBJECT)
+# with different names
+include_directories(AFTER ${CMAKE_CURRENT_BINARY_DIR})
 
 add_flang_library(FortranRuntime
   ISO_Fortran_binding.cpp
   allocatable.cpp
   buffer.cpp
   character.cpp
   connection.cpp
   derived-type.cpp