Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled

Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.

Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.

Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost. 

The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.

Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.

client/mysqldump.c:
  Pass my_free directly as its signature is compatible with the
  callback type -- which wasn't the case for free_table_ent.

3 files changed, 11 insertions, 11 deletions

diff --git a/libmysql/Makefile.am b/libmysql/Makefile.am
index b1d23a175d4..8aa1648c834 100644
--- a/libmysql/Makefile.am
+++ b/libmysql/Makefile.am
@@ -79,7 +79,7 @@ link_sources:
 # a minimal MySQL client library
 #
 # For a really minimal distribution (without debugging code) we could
-# keep only the stubs for safemalloc.c and debug.c
+# keep only the stubs for debug.c
 #
 # A list of needed headers collected from the deps information 000213
 nh =		my_global.h config-win32.h dbug.h errmsg.h \
diff --git a/libmysql/Makefile.shared b/libmysql/Makefile.shared
index 71a4fd867bd..2b413831076 100644
--- a/libmysql/Makefile.shared
+++ b/libmysql/Makefile.shared
@@ -49,7 +49,7 @@ mystringsobjects =	strmov.lo strxmov.lo strxnmov.lo strnmov.lo \
 			ctype-uca.lo xml.lo my_strtoll10.lo str_alloc.lo dtoa.lo
 
 mystringsextra= 	strto.c
-dbugobjects =		dbug.lo # IT IS IN SAFEMALLOC.C sanity.lo
+dbugobjects =		dbug.lo
 mysysheaders =		mysys_priv.h my_static.h
 vioheaders =		vio_priv.h
 mysysobjects1 =		my_init.lo my_static.lo my_malloc.lo my_realloc.lo \
@@ -57,7 +57,7 @@ mysysobjects1 =		my_init.lo my_static.lo my_malloc.lo my_realloc.lo \
 			my_file.lo my_read.lo my_write.lo errors.lo \
 			my_error.lo my_getwd.lo my_div.lo \
 			mf_pack.lo my_mess.lo mf_dirname.lo mf_fn_ext.lo\
-			mf_wcomp.lo typelib.lo safemalloc.lo my_alloc.lo \
+			mf_wcomp.lo typelib.lo my_alloc.lo \
 			mf_format.lo mf_path.lo mf_unixpath.lo my_fopen.lo \
 			my_symlink.lo my_fstream.lo mf_arr_appstr.lo \
 			mf_loadpath.lo my_pthread.lo my_thr_init.lo \
diff --git a/libmysql/libmysql.c b/libmysql/libmysql.c
index 901fa1f0c4c..b69c27731dd 100644
--- a/libmysql/libmysql.c
+++ b/libmysql/libmysql.c
@@ -341,7 +341,7 @@ mysql_connect(MYSQL *mysql,const char *host,
     if (!(res=mysql_real_connect(mysql,host,user,passwd,NullS,0,NullS,0)))
     {
       if (mysql->free_me)
-	my_free((uchar*) mysql,MYF(0));
+	my_free(mysql);
     }
     mysql->reconnect= 1;
     DBUG_RETURN(res);
@@ -457,9 +457,9 @@ my_bool	STDCALL mysql_change_user(MYSQL *mysql, const char *user,
   if (rc == 0)
   {
     /* Free old connect information */
-    my_free(mysql->user,MYF(MY_ALLOW_ZERO_PTR));
-    my_free(mysql->passwd,MYF(MY_ALLOW_ZERO_PTR));
-    my_free(mysql->db,MYF(MY_ALLOW_ZERO_PTR));
+    my_free(mysql->user);
+    my_free(mysql->passwd);
+    my_free(mysql->db);
 
     /* alloc new connect information */
     mysql->user=  my_strdup(user,MYF(MY_WME));
@@ -604,7 +604,7 @@ my_bool handle_local_infile(MYSQL *mysql, const char *net_filename)
 err:
   /* free up memory allocated with _init, usually */
   (*options->local_infile_end)(li_ptr);
-  my_free(buf, MYF(0));
+  my_free(buf);
   DBUG_RETURN(result);
 }
 
@@ -715,7 +715,7 @@ static void default_local_infile_end(void *ptr)
   {
     if (data->fd >= 0)
       my_close(data->fd, MYF(MY_WME));
-    my_free(ptr, MYF(MY_WME));
+    my_free(ptr);
   }
 }
 
@@ -2206,7 +2206,7 @@ int cli_stmt_execute(MYSQL_STMT *stmt)
     }
     result= execute(stmt, param_data, length);
     stmt->send_types_to_server=0;
-    my_free(param_data, MYF(MY_WME));
+    my_free(param_data);
     DBUG_RETURN(result);
   }
   DBUG_RETURN((int) execute(stmt,0,0));
@@ -4707,7 +4707,7 @@ my_bool STDCALL mysql_stmt_close(MYSQL_STMT *stmt)
     }
   }
 
-  my_free((uchar*) stmt, MYF(MY_WME));
+  my_free(stmt);
 
   DBUG_RETURN(test(rc));
 }