commit c85939818d065e4592d0291f1755b3e4add038da
author Tom Finegan <tomfinegan@google.com> Tue Sep 05 11:01:09 2017 -0700
committer Tom Finegan <tomfinegan@google.com> Wed Sep 06 18:06:07 2017 +0000
tree fe1aca0d2281bcf52d4fd4122f93eae902d85512
parent 282e9f25b7960e0b2613a75006254bdd21353d3d

Explicitly support user supplied flags in the CMake build.

Add AOM_EXTRA_<TYPE>_FLAGS variables. Currently AS, C, CXX, and
LINKER are the available type values. These variables are added
to argument strings for each type as the last step in generation
to ensure that user flags have precedence over flags added by
the AOM build itself.

Change-Id: I8e01682ee6c7dad2253e01c446a5ced7d06596c7

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 90f8fea..053df79 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -454,6 +454,9 @@
   set_target_properties(aom PROPERTIES SOVERSION 0)
 endif ()
 
+# Handle user supplied compile and link flags last to ensure they're obeyed.
+set_user_flags()
+
 # Aomedia documentation rule.
 if (ENABLE_DOCS)
   include(FindDoxygen)

build/cmake/compiler_flags.cmake

diff --git a/build/cmake/compiler_flags.cmake b/build/cmake/compiler_flags.cmake
index 8559f37..7d9063f 100644
--- a/build/cmake/compiler_flags.cmake
+++ b/build/cmake/compiler_flags.cmake
@@ -320,4 +320,37 @@
   endif ()
 endfunction ()
 
+# Appends flags in $AOM_EXTRA_<TYPE>_FLAGS variables to the flags used at build
+# time.
+function (set_user_flags)
+  # Linker flags are handled first because some C/CXX flags require that a
+  # linker flag is present at link time.
+  if (AOM_EXTRA_EXE_LINKER_FLAGS)
+    is_flag_present(AOM_EXE_LINKER_FLAGS "${AOM_EXTRA_EXE_LINKER_FLAGS}"
+                    extra_present)
+    if (NOT ${extra_present})
+      require_linker_flag("${AOM_EXTRA_EXE_LINKER_FLAGS}")
+    endif ()
+  endif ()
+  if (AOM_EXTRA_AS_FLAGS)
+    # TODO(tomfinegan): assembler flag testing would be a good thing to have.
+    is_flag_present(AOM_AS_FLAGS "${AOM_EXTRA_AS_FLAGS}" extra_present)
+    if (NOT ${extra_present})
+      append_flag(AOM_AS_FLAGS "${AOM_EXTRA_AS_FLAGS}")
+    endif ()
+  endif ()
+  if (AOM_EXTRA_C_FLAGS)
+    is_flag_present(AOM_C_FLAGS "${AOM_EXTRA_C_FLAGS}" extra_present)
+    if (NOT ${extra_present})
+      require_c_flag("${AOM_EXTRA_C_FLAGS}" YES)
+    endif ()
+  endif ()
+  if (AOM_EXTRA_CXX_FLAGS)
+    is_flag_present(AOM_CXX_FLAGS "${AOM_EXTRA_CXX_FLAGS}" extra_present)
+    if (NOT ${extra_present})
+      require_cxx_flag("${AOM_EXTRA_CXX_FLAGS}" YES)
+    endif ()
+  endif ()
+endfunction ()
+
 endif ()  # AOM_BUILD_CMAKE_COMPILER_FLAGS_CMAKE_