[CMake] UNC-path issue in lists used in set and get_filename_component

[Markus Schwarzenberg]

Hello,

i'm using cmake (2.6.2/WIN32) and running into problems with UNC-paths used 
in the set variant

  set(<variable>  <value>  CACHE <type> <docstring> )

when <value> is a list (of paths) and <type> is FILEPATH. In this case,
the (essential) double slashes // at the beginning of UNC path list 
components get truncated to single slashes, resulting in invalid paths. 

The same problem exists with 

  get_filename_component(<variable> <value> PATH)

Please consider the following test case:

  set (TESTRUN_VAR1 "//server/dir1/file1.txt" "//server/dir1/file2.txt" CACHE STRING "TESTRUN_VAR1")
  message("1: TESTRUN_VAR1 = ${TESTRUN_VAR1}"  )
  set (TESTRUN_VAR2 "//server/dir1/file1.txt" "//server/dir1/file2.txt" CACHE FILEPATH "TESTRUN_VAR2")
  message("2: TESTRUN_VAR2 = ${TESTRUN_VAR2}"  )
  set (TESTRUN_VAR3 "//server/dir1/file1.txt" "//server/dir1/file2.txt" )
  message("3: TESTRUN_VAR3 = ${TESTRUN_VAR3}"  )
  set (TESTRUN_VAR4 "//server/dir1/file1.txt"  CACHE FILEPATH "TESTRUN_VAR4")
  message("4: TESTRUN_VAR4 = ${TESTRUN_VAR4}"  )
  get_filename_component(__OUT "${TESTRUN_VAR1}" PATH)
  message("5: get_filename_component (TESTRUN_VAR1 PATH) = ${__OUT}")
  get_filename_component(__OUT "${TESTRUN_VAR4}" PATH)
  message("6: get_filename_component (TESTRUN_VAR4 PATH) = ${__OUT}")
 

Output:

1: TESTRUN_VAR1 = //server/dir1/file1.txt;//server/dir1/file2.txt
2: TESTRUN_VAR2 = /server/dir1/file1.txt;/server/dir1/file2.txt
3: TESTRUN_VAR3 = //server/dir1/file1.txt;//server/dir1/file2.txt
4: TESTRUN_VAR4 = //server/dir1/file1.txt
5: get_filename_component (TESTRUN_VAR1 PATH) = /server/dir1/file1.txt;/server/dir1
6: get_filename_component (TESTRUN_VAR4 PATH) = //server/dir1


Conclusions:
 1: set works correctly when CACHE STRING is used instead of CACHE FILEPATH
 2: set is wrong when CACHE FILEPATH is used
 3: set works correctly whithout using CACHE ... 
 4: set works correctly with CACHE FILEPATH when <value> is NOT a list
 5: get_filename_component( ... PATH) is wrong when  <value> is a list
 6: get_filename_component( ... PATH) works correctly when  <value> is a NOT list
 
These issues are of practical relevance for example in Find_Package(Boost).
resulting in illegal paths when Boost is located using an UNC-Path.

Is this a known issue, shall i file a bug report, or is the usage of
lists in the above examples wrong ...?

--
Markus Schwarzenberg