Allow disabling thread safety in Makefile.PL

Note that thread safety still cannot be forcefully enabled if the necessary
macros are not defined.

diff --git a/Magic.xs b/Magic.xs
index 947ae72a0246b945f2759deaaa5cbff9afe43382..e6c2fdfb937b1e3f691af80edbdd896a31cf8921 100644 (file)
--- a/Magic.xs
+++ b/Magic.xs
@@ -62,7 +62,9 @@
 #endif
 
 #if VMG_MULTIPLICITY && defined(USE_ITHREADS) && defined(dMY_CXT) && defined(MY_CXT) && defined(START_MY_CXT) && defined(MY_CXT_INIT) && (defined(MY_CXT_CLONE) || defined(dMY_CXT_SV))
-# define VMG_THREADSAFE 1
+# ifndef VMG_THREADSAFE
+#  define VMG_THREADSAFE 1
+# endif
 # ifndef MY_CXT_CLONE
 #  define MY_CXT_CLONE \
     dMY_CXT_SV;                                                      \
@@ -71,6 +73,7 @@
     sv_setuv(my_cxt_sv, PTR2UV(my_cxtp))
 # endif
 #else
+# undef  VMG_THREADSAFE
 # define VMG_THREADSAFE 0
 # undef  dMY_CXT
 # define dMY_CXT      dNOOP