[cmake-developers] [CMake 0014099]: Ninja: CMAKE_${LANG}_FLAGS passed to linker come from incorrect scope

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://cmake.org/Bug/view.php?id=14099 
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Reported By:                Andrey Kamaev
Assigned To:                
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Project:                    CMake
Issue ID:                   14099
Category:                   CMake
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
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Date Submitted:             2013-04-19 15:05 MSD
Last Modified:              2013-04-19 15:05 MSD
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Summary:                    Ninja: CMAKE_${LANG}_FLAGS passed to linker come
from incorrect scope
Description: 
Library/module linker is always called with same compiler flags. CMake embeds
CMAKE_${LANG}_FLAGS from the scope of the first library met by generator into
the generic link rule and uses it for all targets of the same type. But
CMAKE_${LANG}_FLAGS variables are directory scoped and should be different.

Looking into the CMake code I found that any platform having
<LANGUAGE_COMPILE_FLAGS> in link command is affected.

Steps to Reproduce: 
The minimal reproducer is attached. In short:

CMakeLists.txt from the topmost directory:

   cmake_minimum_required(VERSION 2.8.8)
   project(level0)
   set(CMAKE_CXX_FLAGS -msse2 ) # flag itself does not matter
   add_library(lelve0 SHARED level0.cpp)
   add_subdirectory(l1)

CMakeLists.txt from sub-directory:

   project(level1)
   set(CMAKE_CXX_FLAGS -mno-sse2 )
   add_library(lelve1 SHARED level1.cpp)

Resulting link commands from Ninja:

   /usr/bin/c++  -fPIC -msse2   -shared -Wl,-soname,liblelve0.so -o liblelve0.so
CMakeFiles/lelve0.dir/level0.cpp.o
   /usr/bin/c++  -fPIC -msse2   -shared -Wl,-soname,liblelve1.so -o
l1/liblelve1.so l1/CMakeFiles/lelve1.dir/level1.cpp.o

Link commands used by make:

   /usr/bin/c++  -fPIC -msse2   -shared -Wl,-soname,liblelve0.so -o liblelve0.so
CMakeFiles/lelve0.dir/level0.cpp.o
   /usr/bin/c++  -fPIC -mno-sse2   -shared -Wl,-soname,liblelve1.so -o
liblelve1.so CMakeFiles/lelve1.dir/level1.cpp.o
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Issue History 
Date Modified    Username       Field                    Change               
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2013-04-19 15:05 Andrey Kamaev  New Issue                                    
2013-04-19 15:05 Andrey Kamaev  File Added: repro.tar.bz2                    
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