[compiler-rt][cmake] Factor out extend_install_path function

[Ericson2314]

Summary

It is likely to become used again, if other projects want their own per-project
install directory variables. install is removed from the name since it is not inherently about installing.

[Ericson2314]

Rebase to hopefully fix pre-merge CI

[stephenneuendorffer]

Seems like a reasonable refactoring to me.

cmake/Modules/ExtendInstallPath.cmake

1

s/of/or/?

4

It seems odd to me to have the second argument be the return value. I'd prefer having it as the first argument and passing prefix_var as a value, rather than as a variable name.

Since you've named it 'extend_install_path' ten perhaps 'prefix_var' should be 'install_path'?

lastly, the documentation leave something to be desired. I would say something like:
"Extend the path in prefix_var with the relative path in current_segment, returning the result in joined_path. If current_segment is an absolute path then just return it and issue a warning.
Note that the code returns a relative path (avoiding introducing leading slashes) if the prefix_var is empty."

[Ericson2314]

Make changes in response to review

[Ericson2314]

Many thanks @stephenneuendorffer for reviewing! I hope the changes I made are in line with what you were thinking.

cmake/Modules/ExtendInstallPath.cmake

+# Extend path with relative of absolute path, warning in the absolute path
+# case, and being careful to not introduce leading slashes if the original path
+# is empty
+function(extend_install_path prefix_var joined_path current_segment)
+  if("${current_segment}" STREQUAL "")
+    set(temp_path "${${prefix_var}}")
+  elseif("${${prefix_var}}" STREQUAL "")
+    set(temp_path "${current_segment}")
+  elseif(IS_ABSOLUTE "${current_segment}")
+    message(WARNING "Since \"${current_segment}\" is absolute, it overrides ${prefix_var}: \"${${prefix_var}}\".")
+    set(temp_path "${current_segment}")
+  else()
+    set(temp_path "${${prefix_var}}/${current_segment}")
+  endif()
+  set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()

compiler-rt/cmake/base-config-ix.cmake

 # The CompilerRT build system requires CMake version 2.8.8 or higher in order
 # to use its support for building convenience "libraries" as a collection of
 # .o files. This is particularly useful in producing larger, more complex
 # runtime libraries.
 
 include(CheckIncludeFile)
 include(CheckCXXSourceCompiles)
+include(ExtendInstallPath)
 
 check_include_file(unwind.h HAVE_UNWIND_H)
 
 # Used by sanitizer_common and tests.
 check_include_file(rpc/xdr.h HAVE_RPC_XDR_H)
 if (NOT HAVE_RPC_XDR_H)
   set(HAVE_RPC_XDR_H 0)
 endif()

 if("${COMPILER_RT_TEST_COMPILER}" MATCHES "clang[+]*$")
   set(COMPILER_RT_TEST_COMPILER_ID Clang)
 elseif("${COMPILER_RT_TEST_COMPILER}" MATCHES "clang.*.exe$")
   set(COMPILER_RT_TEST_COMPILER_ID Clang)
 else()
   set(COMPILER_RT_TEST_COMPILER_ID GNU)
 endif()
 
-function(extend_install_path joined_path current_segment)
-  if("${current_segment}" STREQUAL "")
-    set(temp_path "${COMPILER_RT_INSTALL_PATH}")
-  elseif("${COMPILER_RT_INSTALL_PATH}" STREQUAL "")
-    set(temp_path "${current_segment}")
-  elseif(IS_ABSOLUTE "${current_segment}")
-    message(WARNING "Since \"${current_segment}\" is absolute, it overrides COMPILER_RT_INSTALL_PATH: \"${COMPILER_RT_INSTALL_PATH}\".")
-    set(temp_path "${current_segment}")
-  else()
-    set(temp_path "${COMPILER_RT_INSTALL_PATH}/${current_segment}")
-  endif()
-  set(${joined_path} "${temp_path}" PARENT_SCOPE)
-endfunction()
-
 if(NOT DEFINED COMPILER_RT_OS_DIR)
   if(ANDROID)
     # The CMAKE_SYSTEM_NAME for Android is Android, but the OS is Linux and the
     # driver will search for compiler-rt libraries in the "linux" directory.
     set(COMPILER_RT_OS_DIR linux)
   else()
     string(TOLOWER ${CMAKE_SYSTEM_NAME} COMPILER_RT_OS_DIR)
   endif()
 endif()
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   set(COMPILER_RT_OUTPUT_LIBRARY_DIR
     ${COMPILER_RT_OUTPUT_DIR}/lib)
-  extend_install_path(default_install_path lib)
+  extend_install_path(COMPILER_RT_INSTALL_PATH default_install_path lib)
   set(COMPILER_RT_INSTALL_LIBRARY_DIR "${default_install_path}" CACHE PATH
     "Path where built compiler-rt libraries should be installed.")
 else(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   set(COMPILER_RT_OUTPUT_LIBRARY_DIR
     ${COMPILER_RT_OUTPUT_DIR}/lib/${COMPILER_RT_OS_DIR})
-  extend_install_path(default_install_path "lib/${COMPILER_RT_OS_DIR}")
+  extend_install_path(COMPILER_RT_INSTALL_PATH default_install_path "lib/${COMPILER_RT_OS_DIR}")
   set(COMPILER_RT_INSTALL_LIBRARY_DIR "${default_install_path}" CACHE PATH
     "Path where built compiler-rt libraries should be installed.")
 endif()
-extend_install_path(default_install_path bin)
+extend_install_path(COMPILER_RT_INSTALL_PATH default_install_path bin)
 set(COMPILER_RT_INSTALL_BINARY_DIR "${default_install_path}" CACHE PATH
   "Path where built compiler-rt executables should be installed.")
-extend_install_path(default_install_path include)
+extend_install_path(COMPILER_RT_INSTALL_PATH default_install_path include)
 set(COMPILER_RT_INSTALL_INCLUDE_DIR "${default_install_path}" CACHE PATH
   "Path where compiler-rt headers should be installed.")
-extend_install_path(default_install_path share)
+extend_install_path(COMPILER_RT_INSTALL_PATH default_install_path share)
 set(COMPILER_RT_INSTALL_DATA_DIR "${default_install_path}" CACHE PATH
   "Path where compiler-rt data files should be installed.")
 
 if(APPLE)
   # On Darwin if /usr/include/c++ doesn't exist, the user probably has Xcode but
   # not the command line tools (or is using macOS 10.14 or newer). If this is
   # the case, we need to find the OS X sysroot to pass to clang.
   if(NOT EXISTS /usr/include/c++)