changed: use PETSC_NULLPTR

for PETSc < 3.19 we define this to PETSC_NULL.
use of PETSC_NULL causes a deprecation warning in 3.19

Author: akva2

src/LinAlg/LinAlgInit.C

@@ -36,7 +36,7 @@ LinAlgInit::LinAlgInit (int argc, char** argv)
 #if defined(HAS_SLEPC)
   SlepcInitialize(&argc,&argv,(char*)0,PETSC_NULL);
 #elif defined(HAS_PETSC)
-  PetscInitialize(&argc,&argv,(char*)0,PETSC_NULL);
+  PetscInitialize(&argc,&argv,(char*)0,PETSC_NULLPTR);
 #endif
 #ifdef HAVE_MPI
 #ifndef HAS_PETSC

src/LinAlg/PETScSupport.h

@@ -41,6 +41,10 @@
 #include "slepceps.h"
 #endif
 
+#ifndef PETSC_NULLPTR
+#define PETSC_NULLPTR PETSC_NULL
+#endif
+
 #else
 typedef int    PetscInt;  //!< To avoid compilation failures
 typedef double PetscReal; //!< To avoid compilation failures