Use __GNUC_PATCHLEVEL__ rather than __GNUC_PATCH__, according to the documentation https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html

Eigen/src/Core/util/Macros.h

diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index 819fa12..2c62e58 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -61,7 +61,7 @@
 
 /// \internal EIGEN_COMP_GNUC set to version (e.g., 951 for GCC 9.5.1) for all compilers compatible with GCC
 #ifdef __GNUC__
-  #define EIGEN_COMP_GNUC (__GNUC__*100+__GNUC_MINOR__*10+__GNUC_PATCH__)
+  #define EIGEN_COMP_GNUC (__GNUC__*100+__GNUC_MINOR__*10+__GNUC_PATCHLEVEL__)
 #else
   #define EIGEN_COMP_GNUC 0
 #endif