Fix errors preventing clean compilation with NDEBUG defined

Summary:
The intent of these changes is to make sure that we'll compile cleanly with `NDEBUG` defined. Clean compilation is necessary for clearly separating and producing release builds. `NDEBUG` macro is //de facto// way to distinguish between debug and release code paths. It is also notably used in `<assert.h>` to determine the behavior of assertions.

There are two types of problems fixed in this set of changes:

  # Incorrect use of assertions, //i.e.//, assertions have side-effects and are evaluating invariants which are actually meant to be executed in release builds as well.
  # Warnings caused by unused variables (which when treated as errors will cause build breaks) which are fixed by adding `MY_ATTRIBUTE((unused))` to the variable definitions.

Test Plan:
  ```
  mysqlbuild.sh
  mysqltest.sh
  mysqltest.sh --testset=RocksDB

  mysqlbuild.sh --release
  mysqltest.sh --release
  mysqltest.sh --release --testset=RocksDB
  ```

Reviewers: jtolmer, tianx

Reviewed By: tianx

Subscribers: webscalesql-eng

Differential Revision: https://reviews.facebook.net/D54111

client/mysqltest.cc

@@ -8707,7 +8707,8 @@ void run_explain(struct st_connection *cn, struct st_command *command,
 char *re_eprint(int err)
 {
   static char epbuf[100];
-  size_t len= my_regerror(MY_REG_ITOA | err, NULL, epbuf, sizeof(epbuf));
+  size_t len MY_ATTRIBUTE((unused)) = my_regerror(MY_REG_ITOA | err, NULL,
+          epbuf, sizeof(epbuf));
   assert(len <= sizeof(epbuf));
   return(epbuf);
 }

fbson/FbsonUpdater.h

@@ -66,13 +66,16 @@ class FbsonUpdater {
 
     // Get the current node and because we want to delete it, pop it from stack
     NodeInfo curr_node = path_node_.back();
-    int pack_size = (int)((char*)curr_node.fbson_value -
+    int pack_size = (int)((char*)
+                          curr_node.fbson_value -
                           curr_node.addr +
                           curr_node.fbson_value->numPackedBytes());
 
     // Move the data after the current node to new place
-    assert(moveTo(curr_node.addr + pack_size,
-                  curr_node.addr));
+    if (!moveTo(curr_node.addr + pack_size,
+                  curr_node.addr)) {
+       return FbsonErrType::E_OUTOFMEMORY;
+    }
     path_node_.pop_back();
     return FbsonErrType::E_NONE;
   }
@@ -273,7 +276,9 @@ class FbsonUpdater {
       if(str_len <= (int)curr->size() &&
          str_len >= ((int)curr->size() * (1.0 - str_shrink_ratio_))){
         // We can update string in place
-        assert(((StringVal*)curr)->setVal(str, str_len));
+        if (!((StringVal*)curr)->setVal(str, str_len)) {
+          return FbsonErrType::E_INVALID_OPER;
+        }
         return FbsonErrType::E_NONE;
       }
     }

regex/main.c

@@ -561,7 +561,7 @@ eprint(err)
 int err;
 {
 	static char epbuf[100];
-	size_t len;
+	size_t len MY_ATTRIBUTE((unused));
 
 	len = my_regerror(MY_REG_ITOA|err, (my_regex_t *)NULL, epbuf, sizeof(epbuf));
 	assert(len <= sizeof(epbuf));

sql/log_event.cc

@@ -11793,7 +11793,9 @@ int Rows_log_event::do_apply_event(Relay_log_info const *rli)
                              &m_cols_ai : &m_cols);
     table_def *tabledef= NULL;
     TABLE *conv_table= NULL;
-    assert(rli->get_table_data(table, &tabledef, &conv_table));
+    bool get_success MY_ATTRIBUTE((unused)) = rli->get_table_data(table,
+            &tabledef, &conv_table);
+    assert(get_success);
     if (tabledef->have_column_names())
     {
       bitmap_clear_all(table->write_set);

tests/bug25714.c

@@ -23,7 +23,7 @@
 int main (int argc, char **argv)
 {
   MYSQL conn;
-  int OK;
+  int OK MY_ATTRIBUTE((unused));
 
   const char* query4= "INSERT INTO federated.t1 SET Value=54";
   const char* query5= "INSERT INTO federated.t1 SET Value=55";