Don't try to use language level TLS on Cygwin.

wilx · wilx · commit 04fcd97d3afb · 2017-01-30T13:28:12.000+01:00
Cygwin passes the compilation and link test in configure script but
fails during linking of the real code, so we want to avoid it. See GCC
PR64697.
diff --git a/configure b/configure
@@ -10585,7 +10585,8 @@ fi
 
 fi
 
-         if test "$target_os" != "darwin" -o "$target_cpu" != "arm"; then :
+               if test \( "$target_os" != "darwin" -o "$target_cpu" != "arm" \) \
+               -a "$target_os" != "cygwin"; then :
 
 
 
diff --git a/configure.ac b/configure.ac
@@ -537,8 +537,11 @@ dnl Multi threaded library.
      [AC_DEFINE([LOG4CPLUS_HAVE_ATOMIC_DEC_UINT_NV])])
 
    dnl Check if TLS is supported, but only if it isn't iOS target, because it
-   dnl is forbidden by Apple Store to use __tlv_* functions.
-   AS_IF([test "$target_os" != "darwin" -o "$target_cpu" != "arm"],
+   dnl is forbidden by Apple Store to use __tlv_* functions. Also, Cygwin
+   dnl passes the compilation and link test here but fails during linking of
+   dnl the real code, so we want to avoid it too. See GCC PR64697.
+   AS_IF([test \( "$target_os" != "darwin" -o "$target_cpu" != "arm" \) \
+               -a "$target_os" != "cygwin"],
      [AX_TLS_SUPPORT])
 
    AH_TEMPLATE([LOG4CPLUS_HAVE_TLS_SUPPORT])
