https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86553
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
We might need something like:
--- a/libstdc++-v3/src/c++98/math_stubs_long_double.cc
+++ b/libstdc++-v3/src/c++98/math_stubs_long_double.cc
@@ -31,6 +31,7 @@
extern "C"
{
#ifndef _GLIBCXX_HAVE_FABSL
+#undef fabsl
long double
fabsl(long double x)
{
Either that, or figure out why _GLIBCXX_HAVE_FABSL is not defined when
apparently it's a macro for fabs
