Change functions to accept const ptrs to allocators

include/rcutils/allocator.h

@@ -39,6 +39,8 @@ extern "C"
  * until all uses of the allocator have been made.
  * Particular care should be taken when giving an allocator to functions like
  * rcutils_*_init() where it is stored within another object and used later.
+ * Developers should note that, while the fields of a const-qualified allocator
+ * struct cannot be modified, the state of the allocator can be modified.
  */
 typedef struct rcutils_allocator_t
 {
@@ -64,7 +66,11 @@ typedef struct rcutils_allocator_t
   /** An error should be indicated by returning `NULL`. */
   void * (*zero_allocate)(size_t number_of_elements, size_t size_of_element, void * state);
   /// Implementation defined state storage.
-  /** This is passed as the final parameter to other allocator functions. */
+  /**
+   * This is passed as the final parameter to other allocator functions.
+   * Note that the contents of the state can be modified even in const-qualified
+   * allocator objects.
+   */
   void * state;
 } rcutils_allocator_t;
 

include/rcutils/repl_str.h

@@ -129,7 +129,7 @@ rcutils_repl_str(
   const char * str,
   const char * from,
   const char * to,
-  rcutils_allocator_t * allocator);
+  const rcutils_allocator_t * allocator);
 
 // Implementation copied from above mentioned source continues in repl_str.c.
 

include/rcutils/types/string_array.h

@@ -90,7 +90,7 @@ rcutils_ret_t
 rcutils_string_array_init(
   rcutils_string_array_t * string_array,
   size_t size,
-  rcutils_allocator_t * allocator);
+  const rcutils_allocator_t * allocator);
 
 /// Finalize a string array, reclaiming all resources.
 /**

src/repl_str.c

@@ -47,7 +47,7 @@ rcutils_repl_str(
   const char * str,
   const char * from,
   const char * to,
-  rcutils_allocator_t * allocator)
+  const rcutils_allocator_t * allocator)
 {
   /* Adjust each of the below values to suit your needs. */
 

src/string_array.c

@@ -39,7 +39,7 @@ rcutils_ret_t
 rcutils_string_array_init(
   rcutils_string_array_t * string_array,
   size_t size,
-  rcutils_allocator_t * allocator)
+  const rcutils_allocator_t * allocator)
 {
   if (!allocator) {
     RCUTILS_SET_ERROR_MSG("allocator is null", rcutils_get_default_allocator())