[sqlite] [patch] fixed memory leak in the ".dump" command of command line tool sqlite-3.7.0.1

[Dominique Pellé]

Hi

I noticed a memory leak when using the .dump command of
command line tool "sqlite3".  I initially saw it when using
spatialite but the same bug exists in latest sqlite-3.7.0.1.   A
block of memory is leaked each time the ".dump" command
is used.

In the following example, I run .dump 3 times and valgrind
finds 3 blocks of memory leaked:

 $ valgrind  --trace-children=yes --leak-check=yes \
     --track-fds=yes ./sqlite3 2> vg.log
SQLite version 3.7.0.1
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> CREATE TABLE t (a INT);
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE t (a INT);
COMMIT;
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE t (a INT);
COMMIT;
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE t (a INT);
COMMIT;
sqlite> .quit

And file vg.log contains:

==5015== 12 bytes in 3 blocks are definitely lost in loss record 10 of 52
==5015==    at 0x4024F70: malloc (vg_replace_malloc.c:236)
==5015==    by 0x4024FFA: realloc (vg_replace_malloc.c:525)
==5015==    by 0x804997A: appendText (shell.c:895)
==5015==    by 0x8049F83: dump_callback (shell.c:1148)
==5015==    by 0x4094027: sqlite3_exec (sqlite3.c:82322)
==5015==    by 0x804AA14: T.339 (shell.c:1197)
==5015==    by 0x804E3EB: do_meta_command (shell.c:1460)
==5015==    by 0x804BC35: process_input (shell.c:2195)
==5015==    by 0x804EED8: main (shell.c:2615)

Following patch fixes it:

$ diff -c shell.c.ORIG shell.c
*** shell.c.ORIG        2010-08-07 11:38:07.715422705 +0200
--- shell.c     2010-08-07 11:38:13.555496088 +0200
***************
*** 1148,1153 ****
--- 1148,1154 ----
     zTmp = appendText(zTmp, zTable, '"');
     if( zTmp ){
       zSelect = appendText(zSelect, zTmp, '\'');
+       free(zTmp);
     }
     zSelect = appendText(zSelect, " || ' VALUES(' || ", 0);
     rc = sqlite3_step(pTableInfo);


Regards
-- Dominique
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