Testing for Memory Leaks

Audio units should not leak memory. This section describes how to test for memory leaks.

1. To test for memory leaks in an audio unit, set the following environment variable:

   export MallocStackLogging=1

2. Execute the auval tool using the w and q switches. The w switch prevents auval from terminating. The q switch suppresses diagnostic output. You will see output similar to that shown in listing 5.

   
   
   

   Listing 5  Preparing to test for memory leaks

   [~] % auval -v aufx bpas appl -w -q sh(6261) malloc: recording malloc stacks to disk using standard recorder sh(6261) malloc: stack logs being written into /tmp/stack-logs.6261.sh.8jZkMX arch(6262) malloc: recording malloc stacks to disk using standard recorder arch(6262) malloc: stack logs being written into /tmp/stack-logs.6262.arch.0SVUSw auvaltool(6262) malloc: recording malloc stacks to disk using standard recorder auvaltool(6262) malloc: stack logs deleted from /tmp/stack-logs.6262.arch.0SVUSw auvaltool(6262) malloc: stack logs being written into /tmp/stack-logs.6262.auvaltool.ahETKI * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * AU Validation Tool Version: 1.2.1b3 Copyright 2003-2007, Apple, Inc. All Rights Reserved. Specify -h (-help) for command options * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * -------------------------------------------------- VALIDATING AUDIO UNIT: 'aufx' - 'bpas' - 'appl' -------------------------------------------------- AU VALIDATION SUCCEEDED.

3. With the -w switch, auval does not terminate. In another shell, you then execute the leaks command (using the pid (process identifier) of the auval process you are testing. In the example you see in listing 6, the pid is 13425. The -q switch suppresses printout from auval.

   
   
   

   Listing 6  Testing for memory leaks

   [~] % leaks 13425 Process 13425: 2780 nodes malloced for 471 KB Process 13425: 0 leaks for 0 total leaked bytes.

4. If your audio unit has memory leaks, the leaks tool prints out a stack log for each leak it detects.

Testing for Memory Smashers: Memory Scribble Test

Audio units should not attempt to use memory that is not theirs. This section and the next describe how to test for out-of-bounds memory usage.

1. To perform memory scribble test on an audio unit, define the following two environment variables:

   export MallocScribble=1

   export MallocGuardEdges=1

2. Execute the auval tool using the q switch. You'll see something like the output shown in listing 7.

   
   
   

   Listing 7  Performing a memory scribble test

   [~] % auval -v aufx bpas appl -q sh(1294) malloc: protecting edges sh(1294) malloc: enabling scribbling to detect mods to free blocks arch(1295) malloc: protecting edges arch(1295) malloc: enabling scribbling to detect mods to free blocks auvaltool(1295) malloc: protecting edges auvaltool(1295) malloc: enabling scribbling to detect mods to free blocks * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * AU Validation Tool Version: 1.2.1b3 Copyright 2003-2007, Apple, Inc. All Rights Reserved. Specify -h (-help) for command options * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * -------------------------------------------------- VALIDATING AUDIO UNIT: 'aufx' - 'bpas' - 'appl' -------------------------------------------------- AU VALIDATION SUCCEEDED.

   In this case we don't need to specify the -w option. We're using the -q option to suppress auval printing.

3. If your audio unit writes to memory beyond its bounds, it will crash. The stack trace of the crash will be located to the position where the the problem exists. The objective here of course is not to crash!

Testing for Memory Smashers: Guard Malloc Test

1. To perform a Guard Malloc test on an audio unit, define the following three environment variables:

   export DYLD_FORCE_FLAT_NAMESPACE=1

   export DYLD_INSERT_LIBRARIES=/usr/lib/libgmalloc.dylib

   export MALLOC_VECTOR_SIZE=1

2. Execute the auval tool using the q switch. You'll see something like the output shown in listing 8.

   
   
   

   Listing 8  Performing a Guard Malloc test

   [~] % auval -v aufx bpas appl -q GuardMalloc: Allocations will be placed on 16 byte boundaries. GuardMalloc: - Some buffer overruns may not be noticed. GuardMalloc: - Applications using vector instructions (e.g., SSE or Altivec) should work. GuardMalloc: GuardMalloc version 18 GuardMalloc: Allocations will be placed on 16 byte boundaries. GuardMalloc: - Some buffer overruns may not be noticed. GuardMalloc: - Applications using vector instructions (e.g., SSE or Altivec) should work. GuardMalloc: GuardMalloc version 18 GuardMalloc: Allocations will be placed on 16 byte boundaries. GuardMalloc: - Some buffer overruns may not be noticed. GuardMalloc: - Applications using vector instructions (e.g., SSE or Altivec) should work. GuardMalloc: GuardMalloc version 18 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * AU Validation Tool Version: 1.2.1b3 Copyright 2003-2007, Apple, Inc. All Rights Reserved. Specify -h (-help) for command options * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * -------------------------------------------------- VALIDATING AUDIO UNIT: 'aufx' - 'bpas' - 'appl' -------------------------------------------------- AU VALIDATION SUCCEEDED.

3. If your audio unit fails the Guard Malloc test, it will crash. The stack trace of the crash will be located to the position where the the problem exists. The objective here of course is not to crash!