From d6ecae779a28d51e669a4c029d00ec57a98f2bc8 Mon Sep 17 00:00:00 2001
From: liaogang <liaogang@baidu.com>
Date: Thu, 6 Jul 2017 11:25:28 +0800
Subject: [PATCH] FIX: propagation dependencies and out of date rebuild

---
 cmake/generic.cmake | 51 ++++++++++++++++++++++++++-------------------
 1 file changed, 30 insertions(+), 21 deletions(-)

diff --git a/cmake/generic.cmake b/cmake/generic.cmake
index cae9524b2..87d8caaec 100644
--- a/cmake/generic.cmake
+++ b/cmake/generic.cmake
@@ -99,15 +99,37 @@ function(merge_static_libs TARGET_NAME)
   set(libs ${ARGN})
   list(REMOVE_DUPLICATES libs)
 
-  # First get the file names of the libraries to be merged
+  # Get all propagation dependencies from the merged libraries
   foreach(lib ${libs})
+    list(APPEND libs_deps ${${lib}_LIB_DEPENDS})
+  endforeach()
+
+  # To produce a library we need at least one source file.
+  # It is created by add_custom_command below and will helps 
+  # also help to track dependencies.
+  set(dummyfile ${CMAKE_CURRENT_BINARY_DIR}/${TARGET_NAME}_dummy.c)
+
+  # Make the generated dummy source file depended on all static input
+  # libs. If input lib changes,the source file is touched
+  # which causes the desired effect (relink).
+  add_custom_command(OUTPUT ${dummyfile}
+    COMMAND ${CMAKE_COMMAND} -E touch ${dummyfile}
+    DEPENDS ${libs})
+
+  # Generate dummy staic lib
+  file(WRITE ${dummyfile} "const char * dummy = \"${dummyfile}\";")
+  add_library(${TARGET_NAME} STATIC ${dummyfile})
+  target_link_libraries(${TARGET_NAME} ${libs_deps})
+
+  foreach(lib ${libs})
+    # Get the file names of the libraries to be merged
     set(libfiles ${libfiles} $<TARGET_FILE:${lib}>)
   endforeach()
 
+  # Get the file name of the generated library
+  set(outlibfile "$<TARGET_FILE:${TARGET_NAME}>")
+
   if(APPLE) # Use OSX's libtool to merge archives
-    set(dummyfile ${CMAKE_CURRENT_BINARY_DIR}/${TARGET_NAME}_dummy.c)
-    file(WRITE ${dummyfile} "const char * dummy = \"${dummyfile}\";")
-    add_library(${TARGET_NAME} STATIC ${dummyfile})
 		add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
       COMMAND rm "${CMAKE_CURRENT_BINARY_DIR}/lib${TARGET_NAME}.a"
       COMMAND /usr/bin/libtool -static -o "${CMAKE_CURRENT_BINARY_DIR}/lib${TARGET_NAME}.a" ${libfiles})
@@ -117,7 +139,8 @@ function(merge_static_libs TARGET_NAME)
       set(objdir ${lib}.objdir)
 
       add_custom_command(OUTPUT ${objdir}
-        COMMAND ${CMAKE_COMMAND} -E make_directory ${objdir})
+        COMMAND ${CMAKE_COMMAND} -E make_directory ${objdir}
+        DEPENDS ${lib})
 
       add_custom_command(OUTPUT ${objlistfile}
         COMMAND ${CMAKE_AR} -x "$<TARGET_FILE:${lib}>"
@@ -125,23 +148,9 @@ function(merge_static_libs TARGET_NAME)
         DEPENDS ${lib} ${objdir}
         WORKING_DIRECTORY ${objdir})
 
-      # Empty dummy source file that goes into merged library
-      set(mergebase ${lib}.mergebase.c)
-      add_custom_command(OUTPUT ${mergebase}
-        COMMAND ${CMAKE_COMMAND} -E touch ${mergebase}
-        DEPENDS ${objlistfile})
-
-      list(APPEND mergebases "${mergebase}")
-    endforeach()
-
-    # We need a target for the output merged library
-    add_library(${TARGET_NAME} STATIC ${mergebases})
-    set(outlibfile "$<TARGET_FILE:${TARGET_NAME}>")
-
-    foreach(lib ${libs})
       add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
-      COMMAND ${CMAKE_AR} ru ${outlibfile} @"../${lib}.objlist"
-      WORKING_DIRECTORY ${lib}.objdir)
+        COMMAND ${CMAKE_AR} ru ${outlibfile} *.o 
+        WORKING_DIRECTORY ${objdir})
     endforeach()
 
     add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
-- 
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