From aea8d18739e062ce2eea7714b40fdb9ee0223cae Mon Sep 17 00:00:00 2001
From: Nils Wentzell <nwentzell@flatironinstitute.org>
Date: Fri, 15 May 2020 14:43:08 -0400
Subject: [PATCH] [cmake] In extract_flags allow extraction of BUILD_INTERFACE
 flags

---
 doc/CMakeLists.txt              |  2 +-
 share/cmake/extract_flags.cmake | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index d2b8576c..8bf5b0bd 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -6,7 +6,7 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/conf.py.in ${CMAKE_CURRENT_BINARY_DIR
 # -----------------------------------------------------------------------------
 add_custom_target(${PROJECT_NAME}_docs_cpp2rst)
 include(${PROJECT_SOURCE_DIR}/share/cmake/extract_flags.cmake)
-extract_flags(app4triqs_c)
+extract_flags(app4triqs_c BUILD_INTERFACE)
 separate_arguments(app4triqs_c_CXXFLAGS)
 macro(generate_docs header_file)
   add_custom_command(
diff --git a/share/cmake/extract_flags.cmake b/share/cmake/extract_flags.cmake
index 0b83247f..dfcf67b0 100644
--- a/share/cmake/extract_flags.cmake
+++ b/share/cmake/extract_flags.cmake
@@ -51,7 +51,13 @@ macro(get_property_recursive)
 endmacro()
 
 # Recursively fetch all compiler flags attached to the interface of a target
-macro(extract_flags target)
+macro(extract_flags)
+
+  cmake_parse_arguments(ARG "BUILD_INTERFACE" "" "" ${ARGN})
+
+  set(target ${ARGV0})
+  unset(${target}_CXXFLAGS)
+  unset(${target}_LDFLAGS)
 
   get_property_recursive(opts TARGET ${target} PROPERTY INTERFACE_COMPILE_OPTIONS)
   foreach(opt ${opts})
@@ -84,8 +90,13 @@ macro(extract_flags target)
   endforeach()
 
   # We have to replace generator expressions explicitly
-  string(REGEX REPLACE "\\$<INSTALL_INTERFACE:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
-  string(REGEX REPLACE "\\$<INSTALL_INTERFACE:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
+  if(ARG_BUILD_INTERFACE)
+    string(REGEX REPLACE "\\$<BUILD_INTERFACE:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
+    string(REGEX REPLACE "\\$<BUILD_INTERFACE:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
+  else()
+    string(REGEX REPLACE "\\$<INSTALL_INTERFACE:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
+    string(REGEX REPLACE "\\$<INSTALL_INTERFACE:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
+  endif()
   string(REGEX REPLACE " [^ ]*\\$<[^ ]*:[^>]*>" "" ${target}_LDFLAGS "${${target}_LDFLAGS}")
   string(REGEX REPLACE " [^ ]*\\$<[^ ]*:[^>]*>" "" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
 endmacro()