(libT) fix a tr_buildPath() bug reported by pea_

libtransmission/utils-test.c

@@ -1,6 +1,7 @@
 #include <stdio.h> /* fprintf */
 #include <string.h> /* strcmp */
 #include "transmission.h"
+#include "platform.h"
 #include "utils.h"
 #include "crypto.h"
 
@@ -118,6 +119,22 @@ test_strstrip( void )
     return 0;
 }
 
+static int
+test_buildpath( void )
+{
+    char * out;
+
+    out = tr_buildPath( "foo", "bar", NULL );
+    check( !strcmp( out, "foo" TR_PATH_DELIMITER_STR "bar" ) );
+    tr_free( out );
+
+    out = tr_buildPath( "", "foo", "bar", NULL );
+    check( !strcmp( out, TR_PATH_DELIMITER_STR "foo" TR_PATH_DELIMITER_STR "bar" ) );
+    tr_free( out );
+
+    return 0;
+}
+
 int
 main( void )
 {
@@ -141,6 +158,8 @@ main( void )
 
     if( ( i = test_strstrip( ) ) )
         return i;
+    if( ( i = test_buildpath( ) ) )
+        return i;
 
     /* test that tr_cryptoRandInt() stays in-bounds */
     for( i = 0; i < 100000; ++i )

libtransmission/utils.c

@@ -615,7 +615,7 @@ tr_buildPath( const char *first_element, ... )
         bufLen += strlen( element ) + 1;
         element = (const char*) va_arg( vl, const char* );
     }
-    pch = buf = tr_new0( char, bufLen );
+    pch = buf = tr_new( char, bufLen );
     va_end( vl );
 
     /* pass 2: build the string piece by piece */
@@ -623,16 +623,19 @@ tr_buildPath( const char *first_element, ... )
     element = first_element;
     while( element ) {
         const size_t elementLen = strlen( element );
-        if( pch != buf )
-            *pch++ = TR_PATH_DELIMITER;
         memcpy( pch, element, elementLen );
         pch += elementLen;
+        *pch++ = TR_PATH_DELIMITER;
         element = (const char*) va_arg( vl, const char* );
     }
     va_end( vl );
 
-    /* sanity checks & return */
+    /* terminate the string.  if nonempty, eat the unwanted trailing slash */
+    if( pch != buf )
+        --pch;
     *pch++ = '\0';
+
+    /* sanity checks & return */
     assert( pch - buf == (off_t)bufLen );
     return buf;
 }