In the Programmer's Guide, the sample code for accessing large objects

from libpq has two functions with memory leaks.

The functions pickout() and overwrite() malloc space for buf which is
never freed.

See
http://www.postgresql.org/users-lounge/docs/7.0/programmer/largeobjects3207.htm

This problem is also in the 6.5 docs at
http://www.postgresql.org/users-lounge/docs/6.5/programmer/x3184.htm

Nishad Prakash

doc/src/sgml/lobj.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/lobj.sgml,v 1.14 2000/12/21 22:55:27 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/lobj.sgml,v 1.15 2001/01/20 00:05:54 momjian Exp $
 -->
 
  <chapter id="largeObjects">
@@ -316,48 +316,52 @@ SELECT lo_export(image.raster, '/tmp/motd') from image
  *--------------------------------------------------------------
  */
 #include &lt;stdio.h&gt;
-#include "libpq-fe.h"
-#include "libpq/libpq-fs.h"
+#include &quot;libpq-fe.h&quot;
+#include &quot;libpq/libpq-fs.h&quot;
 
 #define BUFSIZE          1024
 
 /*
- * importFile *    import file "in_filename" into database as large object "lobjOid"
+ * importFile *    import file &quot;in_filename&quot; into database as large object &quot;lob
+jOid&quot;
  *
  */
-Oid importFile(PGconn *conn, char *filename)
+Oid
+importFile(PGconn *conn, char *filename)
 {
-    Oid lobjId;
-    int lobj_fd;
-    char buf[BUFSIZE];
-    int nbytes, tmp;
-    int fd;
+    Oid         lobjId;
+    int         lobj_fd;
+    char        buf[BUFSIZE];
+    int         nbytes,
+                tmp;
+    int         fd;
 
     /*
      * open the file to be read in
      */
     fd = open(filename, O_RDONLY, 0666);
-    if (fd &lt; 0)  {   /* error */
-     fprintf(stderr, "can't open unix file %s\n", filename);
+    if (fd &lt; 0)
+    {                           /* error */
+        fprintf(stderr, &quot;can't open unix file %s\n&quot;, filename);
     }
 
     /*
      * create the large object
      */
-    lobjId = lo_creat(conn, INV_READ|INV_WRITE);
-    if (lobjId == 0) {
-     fprintf(stderr, "can't create large object\n");
-    }
+    lobjId = lo_creat(conn, INV_READ | INV_WRITE);
+    if (lobjId == 0)
+        fprintf(stderr, &quot;can't create large object\n&quot;);
 
     lobj_fd = lo_open(conn, lobjId, INV_WRITE);
+
     /*
      * read in from the Unix file and write to the inversion file
      */
-    while ((nbytes = read(fd, buf, BUFSIZE)) &gt; 0) {
-     tmp = lo_write(conn, lobj_fd, buf, nbytes);
-     if (tmp &lt; nbytes) {
-         fprintf(stderr, "error while reading large object\n");
-     }
+    while ((nbytes = read(fd, buf, BUFSIZE)) &gt; 0)
+    {
+        tmp = lo_write(conn, lobj_fd, buf, nbytes);
+        if (tmp &lt; nbytes)
+            fprintf(stderr, &quot;error while reading large object\n&quot;);
     }
 
     (void) close(fd);
@@ -366,101 +370,115 @@ Oid importFile(PGconn *conn, char *filename)
     return lobjId;
 }
 
-void pickout(PGconn *conn, Oid lobjId, int start, int len)
+void
+pickout(PGconn *conn, Oid lobjId, int start, int len)
 {
-    int lobj_fd;
-    char* buf;
-    int nbytes;
-    int nread;
+    int         lobj_fd;
+    char       *buf;
+    int         nbytes;
+    int         nread;
 
     lobj_fd = lo_open(conn, lobjId, INV_READ);
-    if (lobj_fd &lt; 0) {
-     fprintf(stderr,"can't open large object %d\n",
-          lobjId);
+    if (lobj_fd &lt; 0)
+    {
+        fprintf(stderr, &quot;can't open large object %d\n&quot;,
+                lobjId);
     }
 
     lo_lseek(conn, lobj_fd, start, SEEK_SET);
-    buf = malloc(len+1);
+    buf = malloc(len + 1);
 
     nread = 0;
-    while (len - nread &gt; 0) {
-     nbytes = lo_read(conn, lobj_fd, buf, len - nread);
-     buf[nbytes] = ' ';
-     fprintf(stderr,"&gt;&gt;&gt; %s", buf);
-     nread += nbytes;
+    while (len - nread &gt; 0)
+    {
+        nbytes = lo_read(conn, lobj_fd, buf, len - nread);
+        buf[nbytes] = ' ';
+        fprintf(stderr, &quot;&gt;&gt;&gt; %s&quot;, buf);
+        nread += nbytes;
     }
-    fprintf(stderr,"\n");
+    free(buf);
+    fprintf(stderr, &quot;\n&quot;);
     lo_close(conn, lobj_fd);
 }
 
-void overwrite(PGconn *conn, Oid lobjId, int start, int len)
+void
+overwrite(PGconn *conn, Oid lobjId, int start, int len)
 {
-    int lobj_fd;
-    char* buf;
-    int nbytes;
-    int nwritten;
-    int i;
+    int         lobj_fd;
+    char       *buf;
+    int         nbytes;
+    int         nwritten;
+    int         i;
 
     lobj_fd = lo_open(conn, lobjId, INV_READ);
-    if (lobj_fd &lt; 0) {
-     fprintf(stderr,"can't open large object %d\n",
-          lobjId);
+    if (lobj_fd &lt; 0)
+    {
+        fprintf(stderr, &quot;can't open large object %d\n&quot;,
+                lobjId);
     }
 
     lo_lseek(conn, lobj_fd, start, SEEK_SET);
-    buf = malloc(len+1);
+    buf = malloc(len + 1);
 
-    for (i=0;i&lt;len;i++)
-     buf[i] = 'X';
+    for (i = 0; i &lt; len; i++)
+        buf[i] = 'X';
     buf[i] = ' ';
 
     nwritten = 0;
-    while (len - nwritten &gt; 0) {
-     nbytes = lo_write(conn, lobj_fd, buf + nwritten, len - nwritten);
-     nwritten += nbytes;
+    while (len - nwritten &gt; 0)
+    {
+        nbytes = lo_write(conn, lobj_fd, buf + nwritten, len - nwritten);
+        nwritten += nbytes;
     }
-    fprintf(stderr,"\n");
+    free(buf);
+    fprintf(stderr, &quot;\n&quot;);
     lo_close(conn, lobj_fd);
 }
 
 /*
- * exportFile *    export large object "lobjOid" to file "out_filename"
+ * exportFile *    export large object &quot;lobjOid&quot; to file &quot;out_filename&quot;
  *
  */
-void exportFile(PGconn *conn, Oid lobjId, char *filename)
+void
+exportFile(PGconn *conn, Oid lobjId, char *filename)
 {
-    int lobj_fd;
-    char buf[BUFSIZE];
-    int nbytes, tmp;
-    int fd;
+    int         lobj_fd;
+    char        buf[BUFSIZE];
+    int         nbytes,
+                tmp;
+    int         fd;
 
     /*
-     * create an inversion "object"
+     * create an inversion &quot;object&quot;
      */
     lobj_fd = lo_open(conn, lobjId, INV_READ);
-    if (lobj_fd &lt; 0) {
-     fprintf(stderr,"can't open large object %d\n",
-          lobjId);
+    if (lobj_fd &lt; 0)
+    {
+        fprintf(stderr, &quot;can't open large object %d\n&quot;,
+                lobjId);
     }
 
     /*
      * open the file to be written to
      */
-    fd = open(filename, O_CREAT|O_WRONLY, 0666);
-    if (fd &lt; 0)  {   /* error */
-     fprintf(stderr, "can't open unix file %s\n",
-          filename);
+    fd = open(filename, O_CREAT | O_WRONLY, 0666);
+    if (fd &lt; 0)
+    {                           /* error */
+        fprintf(stderr, &quot;can't open unix file %s\n&quot;,
+                filename);
     }
 
     /*
      * read in from the Unix file and write to the inversion file
      */
-    while ((nbytes = lo_read(conn, lobj_fd, buf, BUFSIZE)) &gt; 0) {
-     tmp = write(fd, buf, nbytes);
-        if (tmp &lt; nbytes) {
-         fprintf(stderr,"error while writing %s\n",
-              filename);
-     }
+    while ((nbytes = lo_read(conn, lobj_fd, buf, BUFSIZE)) &gt; 0)
+    {
+        tmp = write(fd, buf, nbytes);
+        if (tmp &lt; nbytes)
+        {
+            fprintf(stderr, &quot;error while writing %s\n&quot;,
+                    filename);
+        }
     }
 
     (void) lo_close(conn, lobj_fd);
@@ -470,25 +488,27 @@ void exportFile(PGconn *conn, Oid lobjId, char *filename)
 }
 
 void
-exit_nicely(PGconn* conn)
+exit_nicely(PGconn *conn)
 {
-  PQfinish(conn);
-  exit(1);
+    PQfinish(conn);
+    exit(1);
 }
 
 int
 main(int argc, char **argv)
 {
-    char *in_filename, *out_filename;
-    char *database;
-    Oid lobjOid;
-    PGconn *conn;
-    PGresult *res;
-
-    if (argc != 4) {
-     fprintf(stderr, "Usage: %s database_name in_filename out_filename\n",
-          argv[0]);
-     exit(1);
+    char       *in_filename,
+               *out_filename;
+    char       *database;
+    Oid         lobjOid;
+    PGconn     *conn;
+    PGresult   *res;
+
+    if (argc != 4)
+    {
+        fprintf(stderr, &quot;Usage: %s database_name in_filename out_filename\n&quot;,
+                argv[0]);
+        exit(1);
     }
 
     database = argv[1];
@@ -501,33 +521,34 @@ main(int argc, char **argv)
     conn = PQsetdb(NULL, NULL, NULL, NULL, database);
 
     /* check to see that the backend connection was successfully made */
-    if (PQstatus(conn) == CONNECTION_BAD) {
-     fprintf(stderr,"Connection to database '%s' failed.\n", database);
-     fprintf(stderr,"%s",PQerrorMessage(conn));
-     exit_nicely(conn);
+    if (PQstatus(conn) == CONNECTION_BAD)
+    {
+        fprintf(stderr, &quot;Connection to database '%s' failed.\n&quot;, database);
+        fprintf(stderr, &quot;%s&quot;, PQerrorMessage(conn));
+        exit_nicely(conn);
     }
 
-    res = PQexec(conn, "begin");
+    res = PQexec(conn, &quot;begin&quot;);
     PQclear(res);
 
-    printf("importing file %s\n", in_filename);
+    printf(&quot;importing file %s\n&quot;, in_filename);
 /*  lobjOid = importFile(conn, in_filename); */
     lobjOid = lo_import(conn, in_filename);
 /*
-    printf("as large object %d.\n", lobjOid);
+    printf(&quot;as large object %d.\n&quot;, lobjOid);
 
-    printf("picking out bytes 1000-2000 of the large object\n");
+    printf(&quot;picking out bytes 1000-2000 of the large object\n&quot;);
     pickout(conn, lobjOid, 1000, 1000);
 
-    printf("overwriting bytes 1000-2000 of the large object with X's\n");
+    printf(&quot;overwriting bytes 1000-2000 of the large object with X's\n&quot;);
     overwrite(conn, lobjOid, 1000, 1000);
 */
 
-    printf("exporting large object to file %s\n", out_filename);
+    printf(&quot;exporting large object to file %s\n&quot;, out_filename);
 /*    exportFile(conn, lobjOid, out_filename); */
-    lo_export(conn, lobjOid,out_filename);
+    lo_export(conn, lobjOid, out_filename);
 
-    res = PQexec(conn, "end");
+    res = PQexec(conn, &quot;end&quot;);
     PQclear(res);
     PQfinish(conn);
     exit(0);