[CMake] FIND_PROGRAM Question.

[Brad King]

Lars Pechan wrote:
> Hi there,
> I have a question about using the results of a FIND_PROGRAM on Windows.
> 
> I have a couple of FIND_PROGRAMS going to locate cat and awk (available 
> from the UnixUtils pkg).
> 
> They work fine a return a Unix-style path, i.e.
> ${CAT} = G:/UnixUtils/usr/local/wbin/cat.exe and
> ${AWK} = G:/UnixUtils/usr/local/wbin/gawk.exe.
> 
> I then use these in a custom command like so:
> 
> ADD_CUSTOM_COMMAND(
>   OUTPUT ${SOMEWHERE}/Somefile.txt
>   COMMAND ${CAT}
>   ARGS aFile | ${AWK} -f bFile > ${SOMEWHERE}/Somefile.txt
>   DEPENDS aFile bFile
> )
> 
> Now, CMake (CMakeCVS built 28/3/5) creates this Makefile:
> 
> G:\UnixUtils\usr\local\wbin\cat.exe aFile | 
> G:/UnixUtils/usr/local/wbin/gawk.exe -f bFile ...
> 
> The problem is that CMake correctly generates a correct Windows path for 
> the COMMAND argument but not so when another FIND_PROGRAM entity exists 
> in the ARGS?
> 
> Is there any simple way around this? Is it a bug? Wouldn't it make sense 
> if whenever the result of FIND_PROGRAM is used it is modified for the 
> target platform? (as is the case for ${CAT} above but not ${GAWK}.

This is not a problem with FIND_PROGRAM.  CMake always uses forward 
slashes internally and then converts to the appropriate output path when 
it generates the Makefile.  The problem is that it can only convert 
slashes on the COMMAND part of a custom command.  As far as it knows the 
rest of the arguments are just strings because right now CMake's 
language is untyped.

This is usually not a problem because forward slashes are supposed to be 
valid on Windows when naming files.  They are not valid when naming 
executables to run which is why CMake converts the COMMAND portion. 
Since you are using the pipe syntax then the path to awk should be 
converted also but CMake has no idea it needs to do this.  Converting 
the language to have types could solve the problem but that is not in 
the short term plans.  Recognizing the pipe syntax and converting the 
argument after the pipe is probably a better short term solution. 
Please submit this as a feature request here:

http://www.cmake.org/Bug

Meanwhile I suggest you find another way to generate Somefile.txt.  The 
whole point of CMake is to not depend on a huge number of unix tools 
like cat and awk.  You might be able to get what you want by writing a 
custom command like

COMMAND ${CMAKE_COMMAND}
ARGS -P ${CMAKE_CURRENT_BINARY_DIR}/myconvert.cmake

where myconvert.cmake is a CMake script that has been configured with 
the proper input/output paths.  The script can contain FILE and STRING 
commands to read, process, and write Somefile.txt.

-Brad