From Michael Orlitzky <michael@orlitzky.com> in the original version
of the patch:

This was added upstream when it was pointed out that the codebase
contains undefined behavior that triggers glibcxx's assertions.
Disabling the assertions without fixing the undefined behavior is not
a satisfactory solution, so we drop the override.

diff --git a/configure.ac b/configure.ac
index 96b0223..cdc5618 100644
--- a/configure.ac
+++ b/configure.ac
@@ -48,7 +48,7 @@ AC_CHECK_FUNCS(tgammaf)
 dnl avoid "security" checks for vectors is also included in first.h
 dnl use -std=c++17 -march=native  for vectorclass v2 optimizations
 dnl -DUSE_OBJET_BIDON added because xcas::localisation() does not load locales correctly for modules loaded before main() is executed
-CXXFLAGS="$CXXFLAGS  -U_GLIBCXX_ASSERTIONS -DUSE_OBJET_BIDON"
+CXXFLAGS="$CXXFLAGS -DUSE_OBJET_BIDON"
 
 dnl Define DOUBLEVAL if bigendian
 if test "x$ac_cv_c_bigendian" = "xyes"; then
diff --git a/src/first.h b/src/first.h
index 7852c73..21e15b9 100644
--- a/src/first.h
+++ b/src/first.h
@@ -25,9 +25,9 @@
 #define register 
 
 
-#ifdef _GLIBCXX_ASSERTIONS
-#undef _GLIBCXX_ASSERTIONS
-#endif
+// #ifdef _GLIBCXX_ASSERTIONS
+// #undef _GLIBCXX_ASSERTIONS
+// #endif
 
 #if defined NUMWORKS && !defined SDL_KHICAS
 #define KHICAS 1