[<liblzma>] <add LZMA_API_STATIC in lzma.h for linking static build of liblzma>

[alwendya]

Is your feature request related to a problem? Please describe.

I had problem using liblzma in static inside my program with the triplet x64-windows-static-md.
If I look inside lzma.h main header, it says

"#define LZMA_API_STATIC in your application if you want to link against static liblzma"

I defined LZMA_API_STATIC before including lzma.h but I got linking error telling it doesn't find any function.
In details it is looking for lzma function with the prefix __imp_ (for example __imp_lzma_stream_encoder_mt for lzma_stream_encoder_mt function) but since I'm in static mode, it shouldn't.

I looked further in lzma.h header and there is no usage of the LZMA_API_STATIC flag.

I looked in the original lzma.h file from liblzma github repository and inside their files, they use the static flag for LZMA_API_IMPORT.

VCPGK lzma.h extract :

#ifndef LZMA_API_IMPORT
#  if !1 && defined(_WIN32) && !defined(__GNUC__)
#    define LZMA_API_IMPORT __declspec(dllimport)
#  else
#    define LZMA_API_IMPORT
#  endif
#endif

Original lzma.h extract :

#ifndef LZMA_API_IMPORT
#  if !defined(LZMA_API_STATIC) && defined(_WIN32) && !defined(__GNUC__)
#    define LZMA_API_IMPORT __declspec(dllimport)
#  else
#    define LZMA_API_IMPORT
#  endif
#endif

I switched LZMA_API_IMPORT from original lzma.h and now it works

Proposed solution

Replace !1 by !defined(LZMA_API_STATIC) in lzma.h

VCPGK lzma.h extract :

#ifndef LZMA_API_IMPORT
#  if !1 && defined(_WIN32) && !defined(__GNUC__)
#    define LZMA_API_IMPORT __declspec(dllimport)
#  else
#    define LZMA_API_IMPORT
#  endif
#endif

Original lzma.h extract :

#ifndef LZMA_API_IMPORT
#  if !defined(LZMA_API_STATIC) && defined(_WIN32) && !defined(__GNUC__)
#    define LZMA_API_IMPORT __declspec(dllimport)
#  else
#    define LZMA_API_IMPORT
#  endif
#endif

Describe alternatives you've considered

No response

Additional context

No response

[Mengna-Li]

@alwendya I did not encounter any errors when testing the usage on x64-windows-static and x64-windows-static-md. Can you provide a simple example?

[alwendya]

Thanks @Mengna-Li ,
I build liblzma this way :
vcpkg install liblzma --triplet x64-windows-static-md
I link it under my program (Qt Application compiled with MSVC 2022 ) and run this function

#define LZMA_API_STATIC
#include <lzma.h>

...

bool MainWindow::LZMA_Stream_MT_Compress(const QByteArray& inputFileData,
                                         QByteArray&       outputFileData,
                                         int32_t           compressionLevel,
                                         int32_t           threads)
{
    if (inputFileData.size() == 0) { return false; }

    lzma_mt mt    = {};
    mt.flags      = 0;
    mt.threads    = (threads == -1) ? QThread::idealThreadCount() : threads;
    mt.block_size = 0;
    mt.timeout    = 0;
    mt.preset     = (compressionLevel == -1) ? LZMA_PRESET_DEFAULT : compressionLevel;
    mt.check      = LZMA_CHECK_CRC64;

    lzma_stream strm = LZMA_STREAM_INIT;
    lzma_ret    ret  = lzma_stream_encoder_mt(&strm, &mt);
    if (ret != LZMA_OK) { return false; }

    QByteArray inputBuffer;
    QByteArray outputBuffer(65536, 0); // 64KB buffer

    int64_t Pos = 0;
    while (Pos != inputFileData.size()) {
        inputBuffer    = inputFileData.mid(Pos,
                                        (inputFileData.size() - Pos < 65536)
                                               ? inputFileData.size() - Pos
                                               : 65536);
        Pos           += inputBuffer.size();
        strm.next_in   = reinterpret_cast<const uint8_t*>(inputBuffer.data());
        strm.avail_in  = inputBuffer.size();
        do {
            strm.next_out  = reinterpret_cast<uint8_t*>(outputBuffer.data());
            strm.avail_out = outputBuffer.size();

            ret = lzma_code(&strm, LZMA_RUN);
            if (ret != LZMA_OK && ret != LZMA_STREAM_END) {
                lzma_end(&strm);
                return false;
            }
            outputFileData.append(outputBuffer.mid(0, outputBuffer.size() - strm.avail_out));
        } while (strm.avail_out == 0);
    }
    // Finish compression stream
    strm.next_in  = nullptr;
    strm.avail_in = 0;

    do {
        strm.next_out  = reinterpret_cast<uint8_t*>(outputBuffer.data());
        strm.avail_out = outputBuffer.size();

        ret = lzma_code(&strm, LZMA_FINISH);
        if (ret != LZMA_OK && ret != LZMA_STREAM_END) {
            lzma_end(&strm);
            return false;
        }
        outputFileData.append(outputBuffer.mid(0, outputBuffer.size() - strm.avail_out));
    } while (strm.avail_out == 0);
    lzma_end(&strm);
    return true;
}

When I try to run this function, I get linker error searching from all function with __imp_ like __imp_lzma_code, __imp_lzma_end, etc...
the lzma.h LZMA_API_IMPORT preprocessor works like it's still a DLL and the way for me to make it work was to replace !1 by !defined(LZMA_API_STATIC) like I describeb it in my OP.
When I set that in place, my function works without problem. When I switch back to !1, I get the linker error.

[Neumann-A]

@Mengna-Li API defines need to be burned in for MSBuild consumers or other builds which don't use CMake or pkg-config.