(perl #131786) avoid a duplicate symbol error on _LIB_VERSION

For -flto -mieee-fp builds, the _LIB_VERSION definition in perl.c and
in libieee conflict, causing a build failure.

The test we perform in Configure checks only that such a variable exists
(and is declared), it doesn't check that we can *define* such a variable,
which the code in pp.c tried to do.

So rather than trying to define the variable, just initialize it during
our normal interpreter initialization.

(cherry picked from commit fa2e45943e2b6ce22cf70dba5b47afe73c8c7c80)

1 files changed, 8 insertions, 0 deletions

diff --git a/perl.c b/perl.c
index 829a7abf80..384b2944c5 100644
--- a/perl.c
+++ b/perl.c
@@ -286,6 +286,14 @@ perl_construct(pTHXx)
     PL_localpatches = local_patches;	/* For possible -v */
 #endif
 
+#if defined(LIBM_LIB_VERSION)
+    /*
+     * Some BSDs and Cygwin default to POSIX math instead of IEEE.
+     * This switches them over to IEEE.
+     */
+    _LIB_VERSION = _IEEE_;
+#endif
+
 #ifdef HAVE_INTERP_INTERN
     sys_intern_init();
 #endif