GC_VERSION_ALPHA or GC_MICRO_VERSION?

[Doug Evans]

Hi.
I was looking into the libgc 7.4.0 "GC_MARKERS" bug,
and found that the workaround in Guile is using GC_ALPHA_VERSION
which I can't find in the bdwgc git tree, but I can find GC_VERSION_MICRO.

Since undefined preprocessor macros evaluate to zero this test will
pass for any 7.4.x.


#if (GC_VERSION_MAJOR == 7 && GC_VERSION_MINOR == 4     \
     && GC_ALPHA_VERSION == 0)
  /* BDW-GC 7.4.0 has a bug making it loop indefinitely when using
more
     than one marker thread: <https://github.com/ivmai/bdwgc/pull/30>.
     Work around it by asking for one marker thread.  */
  setenv ("GC_MARKERS", "1", 1);
#endif