From e2f4e9988e66b52463305b84d5878b692393c67e Mon Sep 17 00:00:00 2001
From: Nils Wentzell <nwentzell@flatironinstitute.org>
Date: Tue, 14 Jul 2020 18:29:12 -0400
Subject: [PATCH] [cmake] Extend extract_flags.cmake to treat compiler-specific
 generator expressions properly

---
 share/cmake/extract_flags.cmake | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/share/cmake/extract_flags.cmake b/share/cmake/extract_flags.cmake
index 6bce43c2..b6d11483 100644
--- a/share/cmake/extract_flags.cmake
+++ b/share/cmake/extract_flags.cmake
@@ -93,7 +93,8 @@ macro(extract_flags)
     endif()
   endforeach()
 
-  # We have to replace generator expressions explicitly
+  # ==== We have to replace generator expressions explicitly ====
+
   if(ARG_BUILD_INTERFACE)
     string(REGEX REPLACE "\\$<BUILD_INTERFACE:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
     string(REGEX REPLACE "\\$<BUILD_INTERFACE:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
@@ -101,6 +102,19 @@ macro(extract_flags)
     string(REGEX REPLACE "\\$<INSTALL_INTERFACE:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
     string(REGEX REPLACE "\\$<INSTALL_INTERFACE:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
   endif()
+
+  if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    string(REGEX REPLACE "\\$<\\$<CXX_COMPILER_ID:GNU>:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
+    string(REGEX REPLACE "\\$<\\$<CXX_COMPILER_ID:GNU>:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
+  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    string(REGEX REPLACE "\\$<\\$<CXX_COMPILER_ID:Clang>:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
+    string(REGEX REPLACE "\\$<\\$<CXX_COMPILER_ID:Clang>:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
+  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+    string(REGEX REPLACE "\\$<\\$<CXX_COMPILER_ID:AppleClang>:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
+    string(REGEX REPLACE "\\$<\\$<CXX_COMPILER_ID:AppleClang>:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
+  endif()
+
+  # Remove all remaining generator expressions
   string(REGEX REPLACE " [^ ]*\\$<[^ ]*:[^>]*>" "" ${target}_LDFLAGS "${${target}_LDFLAGS}")
   string(REGEX REPLACE " [^ ]*\\$<[^ ]*:[^>]*>" "" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
 endmacro()