The DLL was compiled directly from sources, without the objects' cache keyed by flags :
after make lib-nomt, make lib-mt kept the DLL without threads (and conversely).
It now uses c_dynamic_library(), as the Unix shared library, with the multi-threading flags
in the cache key ; the resource object is an additional dependency. The import library
is the same for both variants (same exports). With BUILD_SHARED=no, liblz4 builds nothing, as before.
Checked with mingw-w64 : MULTITHREAD=0 / 1 / back to 1 (cached) switch the DLL's thread imports ;
a program linked to the multi-threaded DLL compresses with nbWorkers=4 under wine.
Prototype, not intended for a PR as is.
programs/Makefile probed pthread with a fixed have_pthread.c in its directory
(pre-existing in dev) : concurrent invocations collided (24 / 192 concurrent probes
wrongly reported no threads, producing an lz4 CLI without multi-threading),
and read-only source trees made it fail.
- build/make/lz4defs.make : PTHREAD_PROBE, evaluated with the CC and ALLFLAGS of
the invoking Makefile, within a private temporary directory (mktemp -d).
- lib/Makefile and programs/Makefile employ it (lib/'s copy from previous commit removed).
Validated : probes of lib/ and programs/ (192 concurrent, read-only trees), full tests
MT / no-MT, ASAN+UBSAN, TSAN, make test, wine, CLI build (lz4 multithread, lz4-nomt not),
build policies, install scenarios + test_install.sh.
