cygwin cmake failing with windows-style path names not found

Code
1

I’ve got a multi-language project building both C++ and Java executables. I’ve managed to get this working on a really old Linux (CentOS 7.9) system, and now am trying to build on Windows using Cygwin (this is a code that was originally developed for Linux, so Cygwin is the easiest way to get there). I had a makefile that worked, but was specific to NetBeans. I wanted to bring the build system up to something modern, so am using CMake. But I’m getting an error:

$ cmake --build ../WASP_build
[  1%] Building Java objects for trax_commons.jar
error: file not found: \cygdrive\c\Users\<me>\WASP_build\Trax_Commons\CMakeFiles\trax_commons.dir\java_sources
make[2]: *** [Trax_Commons/CMakeFiles/trax_commons.dir/build.make:388: Trax_Commons/CMakeFiles/trax_commons.dir/java_compiled_trax_commons] Error 3
make[1]: *** [CMakeFiles/Makefile2:404: Trax_Commons/CMakeFiles/trax_commons.dir/all] Error 2
make: *** [Makefile:91: all] Error 2

I don’t know why it’s putting backslashes instead of regular slashes into the path, and when I look for the file at a Cygwin bash prompt, it finds things properly if I replace the backslash with a forward slash.

Version info:

$ cmake --version
cmake version 3.28.3

CMake suite maintained and supported by Kitware (kitware.com/cmake).
2

Here’s my top-level CMakeLists.txt file:

cmake_minimum_required(VERSION 3.10)
project(BlueWASP LANGUAGES CXX C Java)
add_subdirectory(Trax_Commons)

Here’s the bulk of the Trax_Commons/CMakeLists.txt:

cmake_minimum_required(VERSION 3.10)
project(Trax_Commons LANGUAGES Java)

# Enable Java language support in CMake
find_package(Java 1.8 REQUIRED)
include(UseJava)

# Set up Java compiler flags to warn items we care about and ignore others
set(CMAKE_JAVA_COMPILE_FLAGS

    # Invalid UTF-8 characters in our source code, so use ISO-8859-1
    -encoding ISO-8859-1

    # -sunapi flag to Xlint suppresses Sun internal API warnings
    -Xlint:-sunapi -XDenableSunApiLintControl

    # Javac suggests unchecked for seeing a class of warnings usually not reported
    # -Xlint:unchecked

    # Increase maximum warnings so all are displayed
    -Xmaxwarns 10000)

find_jar(PREFUSE NAMES prefuse PATHS ../../COTS_libs/java_lib/prefuse-beta-2009)
find_jar(NUX NAMES nux-1.6 PATHS ../../COTS_libs/java_lib/nux-1.6)
find_jar(XOM NAMES XOM PATHS ../../COTS_libs/java_lib/xom_1.5.0)

set(CMAKE_JAVA_INCLUDE_PATH ${PREFUSE}:${NUX}:${XOM})

add_jar(trax_commons
    INCLUDE_JARS ${PREFUSE} ${NUX} ${XOM}
    MANIFEST manifest.txt
    SOURCES
        src/com/ng/trax/commons/collections/bplustree/ThinBPlusNode.java
        src/com/ng/trax/commons/collections/bplustree/BPlusDuplicateContainer.java
        src/com/ng/trax/commons/collections/bplustree/BPlusNode.java
        ,,,
)
3

This error actually appears to come from the Java compiler installed in Cygwin. When I ran cmake --build <build_dir> -v, I see the invocation of javac using regular Cygwin paths, but the error message using the backslash paths. Perhaps the fault is the JDK I’ve got installed in Cygwin. I did point to a v8/v1.8 JDK available on my system (JAVA_HOME=“C:\Program Files\Amazon Correto\jdk1.8.0_292”), but it seems to be ignored in favor of /cygdrive/c/jdk-15.0.2/bin/java, which I never point to.

4

Further info: The Java compiler isn’t a Cygwin compiler; it’s a Windows compiler. So the Cygwin path to the file to be compiled is unrecognized. Now that I understand the problem, perhaps there’s a better solution.

5

If you build with make VERBOSE=1, can you share the command line for that failing Building Java objects… bit? If there are forward slashes there, CMake seems to be doing the right thing at least. If not, then configuring with cmake --trace-expand might help to see if CMake code is using the wrong slashes at least.