diff --git a/include/libpst-types.h b/include/libpst-types.h
index 2add1df..7be8108 100644
--- a/include/libpst-types.h
+++ b/include/libpst-types.h
@@ -22,7 +22,7 @@ typedef enum {
     IS_PUBLIC       = 0x00000040,   ///< public member of class
 } pst_fun_flags;
 
-
+/// @brief information about function
 typedef struct {
     char*           name;   ///< demangled name of the function. NULL if function name resolution failed
     char*           file;   ///< file name where the function is defined. NULL if library failed to get file name
@@ -70,6 +70,7 @@ typedef enum {
     PARAM_TYPE_FUNCPTR  = 0x04000000,   ///< pointer to function
 } pst_param_flags;
 
+/// @brief information about parameter
 typedef struct {
     char*           name;           ///< parameter's name
     char*           type_name;      ///< name of parameter's type
diff --git a/include/libpst.h b/include/libpst.h
index 1b5760d..94772d9 100644
--- a/include/libpst.h
+++ b/include/libpst.h
@@ -84,9 +84,10 @@ const pst_function_info* pst_get_function_info(pst_function* function);
 int pst_get_register(pst_function* function, int regno, unw_word_t* val);
 
 /**
- * @brief Check memory range of process to validity (i.e. that process has access to this range)
+ * @brief Check memory range of process for validity (i.e. that process has access to this range)
  * @param p pointer to start of range
  * @param size size of range to check
+ * @return zero if range of memory pointed by 'p' is valid
  */
 int pst_pointer_valid(void *p, uint32_t size);
 
diff --git a/src/dwarf/dwarf_call_site.c b/src/dwarf/dwarf_call_site.c
index 353d7e8..680a70b 100644
--- a/src/dwarf/dwarf_call_site.c
+++ b/src/dwarf/dwarf_call_site.c
@@ -125,7 +125,7 @@ bool call_site_handle_dwarf(pst_call_site* site, Dwarf_Die* child)
                         pst_dwarf_expr_fini(&loc);
                         pst_log(SEVERITY_DEBUG, "  DW_AT_GNU_call_site_value:\"%s\" ==> 0x%lX", site->ctx->buff, param->value);
                     } else {
-                        pst_log(SEVERITY_ERROR, "Failed to calculate DW_AT_location expression: %s", site->ctx->buff);
+                        pst_log(SEVERITY_WARNING, "Failed to calculate DW_AT_location expression: %s", site->ctx->buff);
                         del_param(param);
                         pst_dwarf_expr_fini(&loc);
                         return false;
diff --git a/src/dwarf/dwarf_function.c b/src/dwarf/dwarf_function.c
index 1e79201..84dae1c 100644
--- a/src/dwarf/dwarf_function.c
+++ b/src/dwarf/dwarf_function.c
@@ -158,7 +158,7 @@ static bool handle_lexical_block(pst_function* fn, Dwarf_Die* result)
                     pst_log(SEVERITY_DEBUG, "Skipping Lexical block tag 'DW_TAG_inlined_subroutine'");
                     break;
                 default:
-                    pst_log(SEVERITY_DEBUG, "Unknown Lexical block tag 0x%X", dwarf_tag(&child));
+                    pst_log(SEVERITY_WARNING, "Unknown Lexical block tag 0x%X", dwarf_tag(&child));
                     break;
             }
         }while (dwarf_siblingof (&child, &child) == 0);
@@ -372,7 +372,7 @@ bool function_handle_dwarf(pst_function * fn, Dwarf_Die* d)
             // Also handle:
             // DW_AT_inline
             default:
-                pst_log(SEVERITY_DEBUG, "Unknown TAG of function: 0x%X", dwarf_tag(&result));
+                pst_log(SEVERITY_WARNING, "Unknown TAG of function: 0x%X", dwarf_tag(&result));
                 break;
         }
     } while(dwarf_siblingof(&result, &result) == 0);
@@ -464,7 +464,7 @@ void pst_function_fini(pst_function* fn)
     clear(fn);
 
     if(fn->frame) {
-        // use free here because it was allocated out of our control by libdw
+        // use free() here because it was allocated out of our control by libdw
         free(fn->frame);
     }
 
diff --git a/src/dwarf/dwarf_operations.c b/src/dwarf/dwarf_operations.c
index 932158f..120034b 100644
--- a/src/dwarf/dwarf_operations.c
+++ b/src/dwarf/dwarf_operations.c
@@ -16,6 +16,7 @@
 // not implemented operations
 static bool dw_op_notimpl(pst_dwarf_stack* stack, const dwarf_op_map* map, Dwarf_Word op1, Dwarf_Word op2)
 {
+    pst_log(SEVERITY_WARNING, "Not implemented DWARF operation %s(0x%X)", map->op_name, map->op_num);
 	return false;
 }
 
diff --git a/src/dwarf/dwarf_parameter.c b/src/dwarf/dwarf_parameter.c
index e7639f8..3d3fe46 100644
--- a/src/dwarf/dwarf_parameter.c
+++ b/src/dwarf/dwarf_parameter.c
@@ -423,7 +423,7 @@ bool parameter_handle_dwarf(pst_parameter* param, Dwarf_Die* result, pst_functio
             param->info.value = param->location.value;
             param->info.flags |= PARAM_HAS_VALUE;
         } else {
-            pst_log(SEVERITY_ERROR, "Failed to calculate DW_AT_location expression: %s", param->ctx->buff);
+            pst_log(SEVERITY_WARNING, "Failed to calculate DW_AT_location expression: %s", param->ctx->buff);
         }
     } else if(dwarf_hasattr(result, DW_AT_const_value)) {
         param->info.flags |= PARAM_CONST;