[CMake] error executing script with cmake -P

[Alan W. Irwin]

On 2019-10-14 12:00+0100 Edoardo Pasca wrote:

> Dear all,
>
> I am using external project. I would like to patch a source file. I came
> out with a cmake script that does the string replacement I'm interested in.
>
> I tested in a standalone project, with the following CMakeLists.txt
>
> cmake_minimum_required(VERSION 3.4)
> project(patching_string)
> file (STRINGS TestData.py testdata NEWLINE_CONSUME)
> string(REPLACE "sys.prefix" "os.environ[\'SIRF_INSTALL_PATH\']" patched
> ${testdata})
> file( WRITE ${CMAKE_CURRENT_SOURCE_DIR}/TestData.py ${patched} )
>
> and as a matter of facts this does the string replacement I'm interested in.
>
> Good, now I would like to use this to the project I'm really interested in
> which uses the ExternalProject_Add machinery. I added the patch step:
>
> <code>
>
> file (WRITE ${CMAKE_BINARY_DIR}/patch_script.cmake "
> file (STRINGS
> ${${proj}_SOURCE_DIR}/Wrappers/Python/ccpi/framework/TestData.py testdata
> NEWLINE_CONSUME)
> string(REPLACE \"sys.prefix\" \"os.environ[\\\'SIRF_INSTALL_PATH\\\']\"
> patched \${testdata})
> file( WRITE
> ${${proj}_SOURCE_DIR}/Wrappers/Python/ccpi/framework/TestData.py
> \${patched} ) ")
> ExternalProject_Add(
> ...
>
> PATCH_COMMAND ${CMAKE_COMMAND} -P ${CMAKE_BINARY_DIR}/patch_script.cmake
>
> ... )
>
> </code>
>
> Notice that I write the patch_script.cmake before the ExternalProject_Add
>
>
> Now, all of this WORKS. Or at least I get the patch_script.cmake file in
> the proper directoty, with the content I want. However, execution with
> cmake -P patch_script.cmake doesn't work as expected.
>
> I get
> CMake Error at build/patch_script.cmake:3 (string):
>  string sub-command REPLACE requires at least four arguments.
>
> Given that the patch_script.cmake has the same content of the standalone
> CMakeLists.txt above (without the first 2 lines), I don't know where things
> don't go well, except that I execute the script with cmake -P
>
> cmake version 3.15.2
>
> Thanks for any help.

Hi Edo:

This help likely belongs to the "any" category.  :-)  That is, it is just a informed suggestion
that might help you but nothing definite.

It sounds to me from the research you reported above that you have an absolutely clear case where
standalone cmake operating on CMake logic contained in a file (with

cmake_minimum_required(VERSION 3.4)
project(patching_string)

prepended so standalone CMake works fine, but cmake -P operating on *that same file* does
not work.  I suggest you prepare a test tarball containing a file which contains
the CMake logic executed by cmake -P (i.e., all but the first two lines of the above
CMakeLists.txt file),
and the original TestData.py file that logic is supposed to work on.  That simple test
case should help others here (likely not me) replicate the issue you have found and
explain why it occurs for cmake -P but not for the standalone cmake case (with the two
lines prepended, separate build tree, etc., so standalone works).

N.B. Also note that even before that difference is confirmed and
explained, you have the option of either fixing the logic in the cmake
-P case (where the cmake options --debug-output and --trace-expand
might help you figure out exactly what the problem is) or else
adopting the current (prepended) logic for the standalone case and
executing that (rather clumsy, of course) standalone method in your
super-project.

Good luck, and I hope this overview of how I would deal with the
issue you have described is a help to you.

Alan
__________________________
Alan W. Irwin

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.org); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________

Linux-powered Science
__________________________