PetscPoisonMemoryRegion#

Poison a region in memory, making it undereferencable

Synopsis#

static inline PetscErrorCode PetscPoisonMemoryRegion(const void *ptr, size_t size)

Not Available From Fortran

Input Parameters#

ptr - The pointer to the start of the region
size - The size (in bytes) of the region to poison

Notes#

ptr must not be NULL. It is OK to poison the same memory region repeatedly (it is a no-op).

Any attempt to dereference the region after this routine returns results in an error being raised. The memory region may be un-poisoned using PetscUnpoisonMemoryRegion(), making it safe to dereference again.

Example Usage#

  PetscInt *array;

  PetscMalloc1(15, &array);
  // OK, memory is normal
  array[0] = 10;
  array[1] = 15;

  PetscPoisonMemoryRegion(array, 15 * sizeof(*array));
  // ERROR this region is poisoned!
  array[0] = 10;
  // ERROR reading is not allowed either!
  PetscInt v = array[15];

  // OK can re-poison the region
  PetscPoisonMemoryRegion(array, 15 * sizeof(*array));
  // OK can re-poison any subregion too
  PetscPoisonMemoryRegion(array + 5, 1 * sizeof(*array));

  PetscUnpoisonMemoryRegion(array, 1 * sizeof(*array));
  // OK the first entry has been unpoisoned
  array[0] = 10;
  // ERROR the rest of the region is still poisoned!
  array[1] = 12345;

  PetscUnpoisonMemoryRegion(array + 10, sizeof(*array));
  // OK this region is unpoisoned (even though surrounding memory is still poisoned!)
  array[10] = 0;

  PetscInt stack_array[10];

  // OK can poison stack memory as well
  PetscPoisonMemoryRegion(stack_array, 10 * sizeof(*stack_array));
  // ERROR stack array is poisoned!
  stack_array[0] = 10;

Level#

developer

Location#

include/petsc/private/mempoison.h

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