MantisBT - CMake

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Date Submitted

Last Update

0008112

CMake

public

2008-11-18 01:26

2008-11-18 09:59

Reporter

Philip Lowman

Assigned To

Brad King

Priority

normal

Severity

minor

Reproducibility

always

Status

closed

Resolution

fixed

Platform

OS Version

Product Version

CMake-2-6

Target Version

Fixed in Version

Summary

0008112: Regression of CMAKE_INCLUDE_PATH and CMAKE_LIBRARY_PATH with regard to PATH_SUFFIXES

Description

Not sure if this is a bug or not, I suspect it is and it was accidently caused by the addition of CMAKE_PREFIX_PATH. Regardless, it's a change in behavior I noticed between 2.4.8 and 2.6.x that has caused a bit of grief and could continue to cause some people grief so it's worth mentioning.

In CMake 2.4.8 the FIND_LIBRARY and FIND_PATH commands would *always* check for the files in CMAKE_LIBRARY_PATH and CMAKE_INCLUDE_PATH regardless of what was specified in PATH_SUFFIXES. That is to say that PATH_SUFFIXES did not apply to CMAKE_INCLUDE_PATH/CMAKE_LIBRARY_PATH but only to the paths listed after the PATHS command. In CMake 2.6.x that behavior changed. The net effect is that the ability to override the detection of libraries and header files over system defaults with CMAKE_LIBRARY_PATH and CMAKE_INCLUDE_PATH has changed. In fact now your ability to override defaults is at the complete whim of the Find module maintainer and could change at any time.

Example to reproduce:
1. Pick a system header and library already present on your system. For this example I have chosen /usr/lib/libanl* and /usr/include/term.h

2. Create a folder called "my_override" with the following directory structure:
      my_override/include/term.h
      my_override/lib/libanl.a

3. Create this CMakeLists.txt:

PROJECT(foo)
CMAKE_MINIMUM_REQUIRED(VERSION 2.4)

SET(MY_OVERRIDE_ROOT "" CACHE FILEPATH "Override a couple of common libs")
IF(MY_OVERRIDE_ROOT)
   # Works in 2.4.8, fails in 2.6.2
   SET(CMAKE_INCLUDE_PATH ${MY_OVERRIDE_ROOT}/include)
   SET(CMAKE_LIBRARY_PATH ${MY_OVERRIDE_ROOT}/lib)
ENDIF(MY_OVERRIDE_ROOT)

FIND_LIBRARY(ANL_LIBRARY NAMES anl anl2
             HINTS
             $ENV{ANLLOC}
             PATH_SUFFIXES lib64 lib
             PATHS
                /usr/local
                /usr
)
FIND_PATH(TERM_INCLUDE_DIR term.h
             PATH_SUFFIXES include
             PATHS
                /usr/local
                /usr
                /sw
)

4. Using 2.4.8 or 2.6.2 perform an initial configure of your build tree. Note that ANL_LIBRARY and TERM_INCLUDE_DIR are picked up in /usr

5. Delete ANL_LIBRARY and TERM_INCLUDE_DIR from the Cache and specify MY_OVERRIDE_ROOT in the cache to be the /path/to/my_override folder you created earlier. CMake 2.4.8 will discover your new libraries but CMake 2.6.2 will not and will fallback on the system headers/libraries.

You can also reproduce this problem at the command prompt by specifying CMAKE_INCLUDE_PATH and CMAKE_LIBRARY_PATH with the -D directives.

If it was the attempt for CMAKE_INCLUDE_PATH and CMAKE_LIBRARY_PATH to be governed by PATH_SUFFIXES it beckons the question why something like CMAKE_PREFIX_PATH was ever added to begin with? I believe the biggest issue, however, is the "improvement" of Find modules breaking behavior for the end user. Consider the following case:

1. Random FindFoo.cmake changes in CMake trunk from this poorly written example:

FIND_LIBRARY(FOO_LIBRARY NAMES foo
               PATHS
                   /usr/local/lib64
                   /usr/local/lib
                   /usr/lib64
                   /usr/lib
                   /sw/lib64
                   /sw/lib
)

To something not quite as bad thanks to PATH_SUFFIXES

FIND_LIBRARY(FOO_LIBRARY NAMES foo
                    PATH_SUFFIXES lib64 lib
                    PATHS
                        /usr/local
                        /usr
                        /sw
)

Woops, Joe's definition of CMAKE_INCLUDE_PATH (which he was applying in a scripted command line option by the way which has worked since CMake 2.4.x) just broke.

Steps To Reproduce

Additional Information