FMT dependency in ktx is causing a lot issues while compiling.

[Aswin-programmer]

🐞 Issue Description

While building the project with Clang and the project version of {fmt}, compilation fails in certain sections of format.cc and related files. The issue appears in the following code fragments:

if (message.size() <= inline_buffer_size - error_code_size)
    format_to(it, FMT_STRING("{}{}"), message, SEP);
format_to(it, FMT_STRING("{}{}"), ERROR_STR, error_code);
FMT_ASSERT(out.size() <= inline_buffer_size, "");

[Aswin-programmer]

Hey I have found some clues so that you can recreate the issue in your system. I once again tried to compile with the MSVC and I have got no errors. The errors only come when I try to use the Clang compiler in the windows. I lot of issues actually come. Solving one error actually causes other error. Please to help me to fix issue.

[Aswin-programmer]

Hey I have managed to fix all the errors!.

Now its compiling very very will on the windows using the clang compiler.

The problem is that the CMakeList.txt file is written assuming that MSVC will only be used in Windows. So in lot of points its like if its not MSVC then it will automatically set to create the linux style libraries which causes a lot of issues in compiling.

I have actually changed the code in this file:
KTX\external\basis_universal\CMakeLists.txt

This is how I have changed. Now its compiling properly. Please to fix it as a official one so that others will not experience it.

🛠 Proposed Solution (Fix)

The relevant section should be modified as follows (changes are highlighted):

if (NOT MSVC)
    add_compile_options(-g)

    if (BASISU_SAN)
		message("Enabling SAN")
		
        add_compile_options(-fsanitize=address -fno-omit-frame-pointer -fsanitize=undefined -fno-sanitize=alignment)
    endif()



    # --- Start of FIX ---
    # Add common non-MSVC flags (excluding -fPIC for now)
    add_compile_options(-fvisibility=hidden -fno-strict-aliasing -D_LARGEFILE64_SOURCE=1
            -D_FILE_OFFSET_BITS=64 -Wall -Wextra -Wno-unused-local-typedefs
            -Wno-unused-value -Wno-unused-parameter -Wno-unused-variable
            -Wno-misleading-indentation
            -Wno-maybe-uninitialized -Wno-unused-function
            -Wno-stringop-overflow -Wno-unknown-warning-option)

    # Conditionally add -fPIC ONLY on non-Windows platforms
    if (NOT WIN32)
        add_compile_options(-fPIC)
    endif()
    # --- End of FIX ---

    # AppleClang 14 raises this warning in zstd.cpp.
    add_compile_options("$<$<AND:$<CXX_COMPILER_ID:Clang,AppleClang>,$<VERSION_LESS:$<CXX_COMPILER_VERSION>,17>>:-Wno-bitwise-instead-of-logical>")

    add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:-Wno-reorder;-Wno-class-memaccess;-Wno-deprecated-copy>")

    add_compile_options($<$<NOT:$<BOOL:BASISU_BUILD_X64>>:-m32>)
    add_compile_definitions($<$<CONFIG:Debug>:_DEBUG>)
    if (EMSCRIPTEN)
        add_link_options("SHELL:-s ALLOW_MEMORY_GROWTH=1")
    endif()
else()
    add_compile_options("$<$<CXX_COMPILER_ID:Clang>:-Wno-unused-variable;-Wno-unused-function>")
endif()

// After then some lines later:
if (NOT MSVC)
    # For Non-Windows builds, let cmake try and find the system OpenCL headers/libs for us.
    if (BASISU_OPENCL AND OPENCL_FOUND)
        target_compile_definitions(basisu_encoder PRIVATE BASISU_SUPPORT_OPENCL=1)

        target_include_directories(basisu_encoder INTERFACE ${OpenCL_INCLUDE_DIRS})
        target_link_libraries(basisu_encoder INTERFACE ${OpenCL_LIBRARIES})
    endif()
    
    # FIX: Only link 'm' on non-Windows platforms (Linux, macOS)
    # --> BEGIN FIX
    if (NOT WIN32)
        target_link_libraries(basisu_encoder INTERFACE m) 
    endif()
    # <-- END FIX
    
    if(Threads_FOUND AND CMAKE_USE_PTHREADS_INIT)
        target_link_libraries(basisu_encoder INTERFACE Threads::Threads)
    elseif(LINUX)
        target_link_libraries(basisu_encoder INTERFACE dl Threads::Threads)
    endif()
    if (BASISU_STATIC AND MINGW)
        target_link_options(basisu_encoder INTERFACE -static-libgcc -static-libstdc++ -static)
    endif()
else()
    # For Windows builds, we use our local copies of the OpenCL import lib and Khronos headers.
    if (BASISU_OPENCL)
        target_compile_definitions(basisu_encoder PRIVATE BASISU_SUPPORT_OPENCL=1)
        target_include_directories(basisu_encoder INTERFACE "OpenCL")

        if (BASISU_BUILD_X64)
            target_link_libraries(basisu_encoder INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/OpenCL/lib/OpenCL64.lib")
        else()
            target_link_libraries(basisu_encoder INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/OpenCL/lib/OpenCL.lib")
        endif()
    endif()
endif()

[MarkCallow]

This is strange because the basisu code does not use {fmt} and add_compile_options is supposed to only affect options for the current project and any subprojects. The settings should not affect siblings, parent, parent's siblings or other ancestor projects. Only some of the parent's siblings use {fmt}.

Our CI builds with both ClangCL and msvc on Windows and runs our tests suite in both cases. Everything passes. We also build with clang on macOS. Again there were no problems. MSVC is set for the ClangCL case, so I guess you must be using straight clang on Windows. Is that true?

The changes seem reasonable for the purpose of building the basisu library but we need to clear up how these settings are affecting the targets that use {fmt}.

If you wish to make a PR with the fixes please make it against the cmake_fixes branch of https://github.com/KhronosGroup/basis_universal/.

[MarkCallow]

If you wish to make a PR with the fixes please make it against the cmake_fixes branch of https://github.com/KhronosGroup/basis_universal/.

Hold off on that. I am merging in some changes from the upstream basis_universal repo.

[Aswin-programmer]

Sure!.

[MarkCallow]

I've included your changes while updating our fork to the latest basis_universal code. They are also included in BinomialLLC/basis_universal#411. Thanks for the fixes.

I still want to understand why you saw problems in {fmt} until you made these changes. Please explain more.

[Aswin-programmer]

I too have that doubt. For some reason the FMT issue suddenly disappeared. I don't know what caused and how does it automatically disappeared. Glad that my fix worked. I consider myself learning everyday. I am a beginner in graphics programming. I hope that one day I be able to very good opensource software or games using my knowledge. I too have a lot of doubts in graphics programming. If possible please to share some way to communicate you like email or reddit or discord. It would be very very helpful in my journey.

Anyways Thanks for your help,