Fix cmake build on OSX after r249434.

[dawn]

Summary

This fixes the cmake build on OSX when building in a new workspace. It reverts r249434 and instead fixes the issue as proposed in lldb-dev in message 'cmake question and [PATCH] for Undefined symbol "_liblldb_coreVersionString"'. It gets the warning:

ninja: warning: multiple rules generate tools/lldb/source/LLDB_vers.c. builds involving this target will not be correct; continuing anyway

(which no one was able to suggest a fix for in lldb-dev), but at least it fixes the problem without breaking the entire build :)

[zturner]

I can't verify that this works on MacOSX at the moment. Did you verify that this works on other platforms as well?

[dawn]

In D13535#262225, @zturner wrote:

I can't verify that this works on MacOSX at the moment. Did you verify that this works on other platforms as well?

I've confirmed it works on MacOSX - I'll try to test Linux later today if no one beats me to it.

[dawn]

Works fine on Linux too.

[zturner]

Ok, lgtm then.

[dawn]

Can someone accept this patch so I can commit please?

[zturner]

lgtm is just as good as hitting accept in Phabricator, I just can't login
to Phab right now so I'm using email. Feel free to commit

[brucem]

tools/lldb-server/CMakeLists.txt

42 ↗

(On Diff #36798)

Why is this needed?

[dawn]

tools/lldb-server/CMakeLists.txt

42 ↗

(On Diff #36798)

You get undefined symbol otherwise (if you build from scratch).

[dawn]

tools/lldb-server/CMakeLists.txt

42 ↗

(On Diff #36798)

I should clarify - lldb-server needs to link with LLDB_vers.c or you get unresolved symbol (that's the fix at line 38). This sets up the dependency - see example in source/API/CMakeLists.txt.

[brucem]

I think what needs to happen is that you take the add_custom_command and then create a target that will execute the command and only do it once ... I'll provide an example from something else shortly.

(I was about to request changes here when you committed it and closed the revision.)

[brucem]

The way to do this correctly is something like

ADD_CUSTOM_COMMAND(
  OUTPUT whatever.output.file.c
  COMMAND ... whatever ...
  DEPENDS ... whatever ...
)
ADD_CUSTOM_TARGET(whatever-target-name
                  ALL
                  DEPENDS whatever.output.file.c)

[dawn]

I went ahead and committed this since the build was completely broken - I'd be happy to apply any suggestions folks make here in subsequent commits.

[brucem]

I don't know what's broken for you. My build hasn't had any issues on Mac OS X using cmake.

[dawn]

In D13535#262670, @brucem wrote:

The way to do this correctly is something like
...

Can you open a new patch which shows your suggested changes please? Or at least clarify how the add_custom_command should look in this case and where it should go?

[dawn]

In D13535#262672, @brucem wrote:

I don't know what's broken for you. My build hasn't had any issues on Mac OS X using cmake.

In a clean workspace, cmake would fail because LLDB_vers.c hadn't been created yet. You get the error:

CMake Error at cmake/modules/AddLLVM.cmake:401 (add_library):
  Cannot find source file:

    /Users/testuser/build/workspace/LLVM-Clang-LLDB_master_release_OSX/llvm/build_ninja/tools/lldb/source/LLDB_vers.c

  Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .hh .h++ .hm .hpp
  .hxx .in .txx
Call Stack (most recent call first):
  tools/lldb/cmake/modules/AddLLDB.cmake:59 (llvm_add_library)
  tools/lldb/source/API/CMakeLists.txt:9 (add_lldb_library)

[dawn]

FYI - our Jenkins master build just picked up the change and is finally building again - yay!! :)

lldb/trunk/cmake/LLDBDependencies.cmake

if ( CMAKE_SYSTEM_NAME MATCHES "FreeBSD" )
   list(APPEND LLDB_USED_LIBS
     lldbPluginProcessFreeBSD
     lldbPluginProcessPOSIX
     )
 endif ()
 
 # Darwin-only libraries
 if ( CMAKE_SYSTEM_NAME MATCHES "Darwin" )
+  set(LLDB_VERS_GENERATED_FILE ${LLDB_BINARY_DIR}/source/LLDB_vers.c)
+  add_custom_command(OUTPUT ${LLDB_VERS_GENERATED_FILE}
+    COMMAND ${LLDB_SOURCE_DIR}/scripts/generate-vers.pl
+            ${LLDB_SOURCE_DIR}/lldb.xcodeproj/project.pbxproj liblldb_core
+            > ${LLDB_VERS_GENERATED_FILE})
+
+  set_source_files_properties(${LLDB_VERS_GENERATED_FILE} PROPERTIES GENERATED 1)
   list(APPEND LLDB_USED_LIBS
     lldbPluginDynamicLoaderDarwinKernel
     lldbPluginObjectFileMachO
     lldbPluginProcessMachCore
     lldbPluginProcessMacOSXKernel
     lldbPluginSymbolVendorMacOSX
     )
 endif()

lldb/trunk/source/CMakeLists.txt

 include_directories(.)
 
 if ( CMAKE_SYSTEM_NAME MATCHES "Linux" )
 include_directories(
   Plugins/Process/Linux
   Plugins/Process/POSIX
   )
 endif ()
 
 if ( CMAKE_SYSTEM_NAME MATCHES "FreeBSD" )
 include_directories(
   Plugins/Process/FreeBSD
   Plugins/Process/POSIX
   )
 endif ()
 
-if ( CMAKE_SYSTEM_NAME MATCHES "Darwin" )
-  set(LLDB_VERS_GENERATED_FILE ${LLDB_BINARY_DIR}/source/LLDB_vers.c)
-  add_custom_command(OUTPUT ${LLDB_VERS_GENERATED_FILE}
-    COMMAND ${LLDB_SOURCE_DIR}/scripts/generate-vers.pl
-            ${LLDB_SOURCE_DIR}/lldb.xcodeproj/project.pbxproj liblldb_core
-            > ${LLDB_VERS_GENERATED_FILE})
-
-  set_source_files_properties(${LLDB_VERS_GENERATED_FILE} PROPERTIES GENERATED 1)
-endif ()
-
 add_lldb_library(lldbBase
   lldb.cpp
-   ${LLDB_VERS_GENERATED_FILE}
   )
 
 add_subdirectory(Breakpoint)
 add_subdirectory(Commands)
 add_subdirectory(Core)
 add_subdirectory(DataFormatters)
 add_subdirectory(Expression)
 add_subdirectory(Host)

lldb/trunk/tools/lldb-server/CMakeLists.txt

if (BUILD_SHARED_LIBS )
   target_link_libraries(lldb-server ${LLDB_SYSTEM_LIBS})
 else()
   add_lldb_executable(lldb-server
     lldb-gdbserver.cpp
     lldb-platform.cpp
     lldb-server.cpp
     LLDBServerUtilities.cpp
     ../../source/lldb.cpp
+    ${LLDB_VERS_GENERATED_FILE}
     )
 
+  if (LLDB_VERS_GENERATED_FILE)
+    add_dependencies(lldb-server swig_wrapper)
+  endif()
+
   # The Darwin linker doesn't understand --start-group/--end-group.
   if (LLDB_LINKER_SUPPORTS_GROUPS)
     target_link_libraries(lldb-server
                           -Wl,--start-group ${LLDB_USED_LIBS} -Wl,--end-group)
     target_link_libraries(lldb-server
                           -Wl,--start-group ${CLANG_USED_LIBS} -Wl,--end-group)
   else()
     target_link_libraries(lldb-server ${LLDB_USED_LIBS})