[PATCH] D103044: [docs] [CMake] Change recommendations for how to use LLVM_DEFINITIONS

[Martin Storsjö via Phabricator via llvm-commits]

mstorsjo created this revision.
mstorsjo added reviewers: phosek, beanz, smeenai.
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LLVM_DEFINITIONS is a string variable containing a list of arguments
to pass to the compiler. When CMake's add_definitions is passed a
string variable, this is interpreted as one argument. To make it
behave properly, the string variable needs to be split into a list.

Despite the fact that add_definitions isn't supposed to be used like
the LLVM docs recommended, it worked fine in practice in many cases.
If the first argument in LLVM_DEFINITIONS is of the form -DFOO=42
instead of plain -DFOO, the rest of the string is treated as value
to this define. I.e. if LLVM_DEFINITIONS consists of `-DFOO=42 -DBAR`,
CMake ended up passing `-DFOO="42 -DBAR"` to the compiler.

See https://gitlab.kitware.com/cmake/cmakissues/22162
for discussion on the matter.

Changing LLVM_DEFINITIONS to be a list variable would possibly be
more disruptive; instead keep the variable defined as before but
change the recommendation for how to use it. Then projects using it
can gradually be updated to follow the new recommendation.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D103044

Files:
  llvm/docs/CMake.rst


Index: llvm/docs/CMake.rst
===================================================================
--- llvm/docs/CMake.rst
+++ llvm/docs/CMake.rst
@@ -770,7 +770,8 @@
   # for your compiler.
 
   include_directories(${LLVM_INCLUDE_DIRS})
-  add_definitions(${LLVM_DEFINITIONS})
+  separate_arguments(LLVM_DEFINITIONS_LIST NATIVE_COMMAND ${LLVM_DEFINITIONS})
+  add_definitions(${LLVM_DEFINITIONS_LIST})
 
   # Now build our tools
   add_executable(simple-tool tool.cpp)
@@ -870,7 +871,8 @@
 
   find_package(LLVM REQUIRED CONFIG)
 
-  add_definitions(${LLVM_DEFINITIONS})
+  separate_arguments(LLVM_DEFINITIONS_LIST NATIVE_COMMAND ${LLVM_DEFINITIONS})
+  add_definitions(${LLVM_DEFINITIONS_LIST})
   include_directories(${LLVM_INCLUDE_DIRS})
 
   add_subdirectory(<pass name>)


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