---
name: "njamdpm"
section: "1"
platform: "linux"
package: "njamd"
version: "0.9.3pre2-4"
release: "Debian 3.0 (Woody)"
platforms: ["linux"]
url: "https://new.carta.tech/njamdpm"
---

# njamdpm(1)

Not Just Another Malloc Debugger Post-Mortem

## NAME

njamdpm - Not Just Another Malloc Debugger Post-Mortem

## SYNOPSIS

**njamdpm** \[*OPTIONS*\] \<*HEAP FILE*\>

## DESCRIPTION

njamdpm is a companion utility that allows you to examine the persistent heap saved by  [**libnjamd**(3)](/libnjamd/3.md)  You can do things like query for certain addresses, show memory leaks, and show all past allocated memory. As of  *NJAMD* 0.6.0, [**gdb**(1)](/gdb/1.md)  is required to make sense of the return addresses.

## USAGE

### Options

- **HEAP FILE**

  The heap file will be in the current directory with a name of the form *njamd-\<pid\>-heap*,  but only if  **NJAMD\_PERSISTANT\_HEAP** was in the environment at the time of program execution

- **-a address**

  Search through the heap file for a chunk of memory that contains  *address.* This can be VERY helpful when using gdb. Simply find the address that you accessed to cause the segmentation fault, use **njamdpm** to look it up in the heap, and viola! You have all sorts of info about the chunk: When it was allocated, when it was freed, how big is is, etc.

- **-d depth**

  When displaying return address info, only display  **depth** return addresses. The max is specified in ./include/lib/njamd.h in the define **TRACE\_DEPTH** (default is 3).

- **-t**

  Trim the heap file down to only the used portion. This is useful if for some reason the program somehow exits without trimming its own heap file down first. Note that when the heap file appears huge it's not actually taking up disk space.

- **-s**

  Dump basic status info about peak memory usage, NJAMD overhead, etc. Useful for determining if you should buy more ram, or write me an angry email :)

- **-l**

  Dump memory leaks in the heap. Also shows you info about where the memory was leaked, along with a total. Do note that this total and the subtotals are *aligned* bytes. They are aligned to the alignment of your architecture, or as specified by the value the  **NJAMD\_ALIGN** environment variable had when the heap was created.

- **-f**

  Dump freed memory in the heap. This option is only available if *LIBNJAMD* ran without  **NJAMD\_CHK\_FREE=none** set.

### Using gdb with njamdpm

When a segmentation fault happens, it's because, of course, you accessed an invalid address. So all you need to do is get gdb to give you the address you accessed, and then feed it to njamdpm. Ie if the segfault occurs on a line that does buf\[i\] = 2, issue **print &buf\[i\]** to gdb. Note that  [**libnjamd**(3)](/libnjamd/3.md)  now has a function \_\_nj\_ptr\_info that can be called from gdb that performs all this without njamdpm.

To get gdb to translate these return addresses into something meaningful, issue

**info line \*0xaddress**

to obtain the line number of the allocation request, or

**list \*0xaddress**

to see the adjacent code as well.

## NOTES

Eventually I hope to add symbol translation right into njamdpm.

## AUTHORS

```
Mike Perry <mikepery@fscked.org>
```

## SEE ALSO

**http://freshmeat.net/appindex/development/debugging.html**

[**njamd**(3)](/njamd/3.md), [**efence**(3)](/efence/3.md), [**malloc**(3)](/malloc/3.md), [**mmap**(2)](/mmap/2.md), [**mprotect**(2)](/mprotect/2.md)