fix compile error

.gitignore

@@ -23,4 +23,5 @@ CMakeFiles/
 doc/html
 make.deps
 src/emacs/dependencies
-compile_commands.json
+compile_commands.json
+.cache

src/CMakeLists.txt

@@ -4,6 +4,14 @@ set(LEAN_VERSION_MAJOR 0)
 set(LEAN_VERSION_MINOR 2)
 set(LEAN_VERSION_PATCH 0)
 
+# Generate the `compile_commands.json` file.
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON CACHE INTERNAL "")
+
+if(CMAKE_EXPORT_COMPILE_COMMANDS)
+  set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES
+    ${CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES})
+endif()
+
 if (NOT CMAKE_BUILD_TYPE)
   message(STATUS "No build type selected, default to Release")
   set(CMAKE_BUILD_TYPE "Release")

src/util/lp/permutation_matrix.h

@@ -123,7 +123,7 @@ namespace lean {
 
         unsigned size() const { return static_cast<unsigned>(m_rev.size()); }
 
-        unsigned * values() const { return m_permutation; }
+        const unsigned * values() const { return m_permutation.data(); }
     }; // end of the permutation class
 
 #ifdef LEAN_DEBUG