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INSTALL
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-------------------------------------------------------------------------------
2.1 How to Install the Library
==============================
To configure, compile, and install the library, follow these steps
carefully.
1. Make sure you have downloaded the latest version of the library
available from the home page at URL `http://dmalloc.com/'.
2. The release files have a `.tgz' file extension which means that
they are a tar'd gzip'd directory of files. You will need to
ungzip and then untar the release file into your source work
directory. You may have to rename the file to `.tar.gz' to get
some old zip programs to handle the file correctly.
3. You may want to edit or at least review the settings in
`settings.dist' to tune specific features of the library. The
`configure' script will copy this file to `settings.h' which is
where you should be adding per-architecture settings.
4. Type `sh ./configure' to configure the library. You may want to
first examine the `config.help' file for some information about
configure. You may want to use the `--disable-cxx' option if you
do not want the Makefile to build the C++ version of dmalloc. You
may want to use the `--enable-threads' option to build the
threaded version of dmalloc. You may want to use the
`--enable-shlib' option to build the shared versions of the
dmalloc libraries. `sh ./configure --help' lists the available
options to configure. Configure should generate the `Makefile'
and configuration files automatically.
5. You may want to examine the `Makefile' and `conf.h' files created
by configure to make sure it did its job correctly.
6. You might want to tune the settings in `settings.h' file to tune
the library to the local architecture. This file contains relevant
settings if you are using pthreads or another thread library.
*Note Using With Threads::. The `configure' script created this
file from the `settings.dist' file. Any permanent changes to these
settings should made to the `settings.dist' file. You then can run
`config.status' to re-create the `settings.h' file.
7. The `DMALLOC_SIZE' variable gets auto-configured in `dmalloc.h.2'
but it may not generate correct settings for all systems. You may
have to alter the definitions in this file to get things to stop
complaining when you go to compile about the size arguments to
malloc routines. Comments on this please.
8. Typing `make' should be enough to build `libdmalloc.a', and
`dmalloc' program. If it does not work, please see if there are
any notes in the contrib directory about your system-type. If not
and you figure your problem out, please send me some notes so
future users can profit from your experiences.
_NOTE_: You may experience some errors compiling some of the
`return.h' assembly macros which attempt to determine the callers
address for logging purposes. *Note Portability::. You may want
to first try disabling any compiler optimization flags. If this
doesn't work then you may need to disable the `USE_RETURN_MACROS'
variable in the `settings.h' file.
_NOTE_: The code is dependent on an ANSI-C compiler. If the
configure script gives the `WARNING' that you do not have an ANSI-C
compiler, you may still be able to add some sort of option to your
compiler to make it ANSI. If there such is an option, please send
it to the author so it can be added to the configure script.
9. If you use threads and did not add the `--enable-threads' argument
to configure, typing `make threads' should be enough to build
`libdmallocth.a' which is the threaded version of the library.
This may or may not work depending on the configuration scripts
ability to detect your local thread functionality. Feel free to
send me mail with improvements.
See the section of the manual on threads for more information about
the operation of the library with your threaded program. *Note
Using With Threads::.
10. If you have a C++ compiler installed, the library should have
automatically built `libdmallocxx.a' which is the C++ version of
the library. If it was not done automatically, you can build it by
typing `make cxx'. You should link this library into your C++
programs instead of `libdmalloc.a'. See the `dmallocc.cc' C++
file which contains basic code to overload the `new', `new[]',
`delete', and `delete[]' C++ operators. My apologies on the
minimal C++ support. I am still living in a mostly C world. Any
help improving this interface without sacrificing portability
would be appreciated.
11. Typing `make light' should build and run the `dmalloc_t' test
program through a set of light trials. By default this will
execute `dmalloc_t' 5 times - each time will execute 10,000 malloc
operations in a very random manner. Anal folks can type `make
heavy' to up the ante. Use `dmalloc_t --usage' for the list of all
`dmalloc_t' options.
12. Typing `make install' should install the `libdmalloc.a' library in
`/usr/local/lib', the `dmalloc.h' include file in
`/usr/local/include', and the `dmalloc' utility in
`/usr/local/bin'. You may also want to type `make installth' to
install the thread library into place and/or `make installcc' to
install the C++ library into place.
You may have specified a `--prefix=PATH' option to configure in
which case `/usr/local' will have been replaced with `PATH'.
See the "Getting Started" section to get up and running with the
library. *Note Getting Started::.
-------------------------------------------------------------------------------
2.2 Getting Started with the Library
====================================
This section should give you a quick idea on how to get going.
Basically, you need to do the following things to make use of the
library:
1. Make sure you have downloaded the latest version of the library
available from the home page at URL `http://dmalloc.com/'.
2. Follow the installation instructions on how to configure, make,
and install the library (i.e. type: `make install'). *Note
Installation::.
3. You need to make sure that the library configuration and build
process above was able to locate one of the `on_exit' function,
`atexit' function, or had compiler destructor support. If one of
these functions or support is available then the dmalloc library
should be able to automatically shut itself down when the program
exits. This causes the memory statistics and unfreed information
to be dumped to the log file. However, if your system has none of
the above, then you will need to call `dmalloc_shutdown' yourself
before your program exits.
4. To get the dmalloc utility to work you need to add an alias for
dmalloc to your shell's runtime configuration file if supported.
The idea is to have the shell capture the dmalloc program's output
and adjust the environment.
After you add the alias to the shell config file you need to log
out and log back in to have it take effect, or you can execute the
appropriate command below on the command line directly. After you
setup the alias, if you enter `dmalloc runtime' and see any output
with DMALLOC_OPTIONS in it then the alias did not take effect.
Bash, ksh, and zsh (`http://www.zsh.org/') users should add the
following to their `.bashrc', `.profile', or `.zshrc' file
respectively (notice the `-b' option for bourne shell output):
function dmalloc { eval `command dmalloc -b $*`; }
If your shell does not support the `command' function then try:
function dmalloc { eval `\dmalloc -b $*`; }
or
function dmalloc { eval `/usr/local/bin/dmalloc -b $*`; }
If you are still using csh or tcsh, you should add the following to
your `.cshrc' file (notice the `-C' option for c-shell output):
alias dmalloc 'eval `\dmalloc -C \!*`'
If you are using rc shell, you should add the following to your
`.rcrc' file (notice the `-R' option for rc-shell output):
fn dmalloc {eval `{/usr/local/bin/dmalloc $*}}
5. Although not necessary, you may want to include `dmalloc.h' in
your C files and recompile. This will allow the library to report
the file/line numbers of calls that generate problems. *Note
Allocation Macros::. It should be inserted at the _bottom_ of
your include files as to not conflict with wother includes. You
may want to ifdef it as well and compile with `cc -DDMALLOC ...':
/* other includes above ^^^ */
#ifdef DMALLOC
#include "dmalloc.h"
#endif
6. Another optional task is to compile all of your source with the
`dmalloc.h' with the `DMALLOC_FUNC_CHECK' compilation flag. This
willallow the library to check all of the arguments of a number of
common string and utility routines. *Note Argument Checking::.
cc -DDMALLOC -DDMALLOC_FUNC_CHECK file.c
7. Link the dmalloc library into your program. The dmalloc library
should probably be placed at or near the end of the library list.
8. Enable the debugging features by typing `dmalloc -l logfile -i 100
low' (for example). You should not see any messages printed by
the dmalloc utility (see NOTE below). This will:
* Set the malloc logfile name to `logfile' (`-l logfile'). For
programs which change directories, you may want to specify the
full path to your logfile.
* Have the library check itself every 100 iterations (`-i 100').
This controls how fast your program will run. Larger numbers
check the heap less and so it will run faster. Lower numbers
will be more likely to catch memory problems.
* Enable a number of debug features (`low'). You can also try
`runtime' for minimal checking or `medium' or `high' for more
extensive heap verification.
* By default, the low, medium, and high values enable the
`error-abort' token which will cause the library to abort and
usually dump core immediately upon seeing an error. *Note
Dumping Core::. You can disable this feature by entering
`dmalloc -m error-abort' (-m for minus) to remove the
`error-abort' token and your program will just log errors and
continue.
`dmalloc --usage' will provide verbose usage info for the dmalloc
program. *Note Dmalloc Program::.
You may also want to install the `dmallocrc' file in your home
directory as `.dmallocrc'. This allows you to add your own
combination of debug tokens. *Note RC File::.
_NOTE_: The output from the dmalloc utility should be captured by
your shell. If you see a bunch of stuff which includes the string
`DMALLOC_OPTIONS' then the alias you should have created above is
not working and he environmental variables are not being set. Make
sure you've logged out and back in to have the alias take effect.
9. Run your program, examine the logfile that should have been
created by `dmalloc_shutdown', and use its information to help
debug your program.
File: dmalloc.info, Node: Allocation Basics, Next: Features, Prev: Getting Started, Up: Overview
2.3 Basic Description of Terms and Functions
============================================
* Menu:
* Basic Definitions:: General memory terms and concepts.
* Malloc Functions:: Functionality supported by all malloc libs.
File: dmalloc.info, Node: Basic Definitions, Next: Malloc Functions, Prev: Allocation Basics, Up: Allocation Basics
2.3.1 General Memory Terms and Concepts
---------------------------------------
Any program can be divided into 2 logical parts: text and data. Text is
the actual program code in machine-readable format and data is the
information that the text operates on when it is executing. The data,
in turn, can be divided into 3 logical parts according to where it is
stored: "static", "stack", and "heap".
Static data is the information whose storage space is compiled into
the program.
/* global variables are allocated as static data */
int numbers[10];
main()
{
...
}
Stack data is data allocated at runtime to hold information used
inside of functions. This data is managed by the system in the space
called stack space.
void foo()
{
/* this local variable is stored on the stack */
float total;
...
}
main()
{
foo();
}
Heap data is also allocated at runtime and provides a programmer with
dynamic memory capabilities.
main()
{
/* the address is stored on the stack */
char * string;
...
/*
* Allocate a string of 10 bytes on the heap. Store the
* address in string which is on the stack.
*/
string = (char *)malloc(10);
...
/* de-allocate the heap memory now that we're done with it */
(void)free(string);
...
}
It is the heap data that is managed by this library.
Although the above is an example of how to use the malloc and free
commands, it is not a good example of why using the heap for runtime
storage is useful.
Consider this: You write a program that reads a file into memory,
processes it, and displays results. You would like to handle files with
arbitrary size (from 10 bytes to 1.2 megabytes and more). One problem,
however, is that the entire file must be in memory at one time to do the
calculations. You don't want to have to allocate 1.2 megabytes when you
might only be reading in a 10 byte file because it is wasteful of system
resources. Also, you are worried that your program might have to handle
files of more than 1.2 megabytes.
A solution: first check out the file's size and then, using the
heap-allocation routines, get enough storage to read the entire file
into memory. The program will only be using the system resources
necessary for the job and you will be guaranteed that your program can
handle any sized file.
File: dmalloc.info, Node: Malloc Functions, Prev: Basic Definitions, Up: Allocation Basics
2.3.2 Functionality Supported by All Malloc Libraries
-----------------------------------------------------
All malloc libraries support 4 basic memory allocation commands. These
include "malloc", "calloc", "realloc", and "free". For more
information about their capabilities, check your system's manual pages
- in unix, do a `man 3 malloc'.
-- Function: void *malloc ( unsigned int SIZE )
Usage: `pnt = (type *)malloc(size)'
The malloc routine is the basic memory allocation routine. It
allocates an area of `size' bytes. It will return a pointer to
the space requested.
-- Function: void *calloc ( unsigned int NUMBER, unsigned intSIZE )
Usage: `pnt = (type *)calloc(number, size)'
The calloc routine allocates a certain `number' of items, each of
`size' bytes, and returns a pointer to the space. It is
appropriate to pass in a `sizeof(type)' value as the size argument.
Also, calloc nulls the space that it returns, assuring that the
memory is all zeros.
-- Function: void *realloc ( void *OLD_PNT, unsigned int NEW_SIZE )
Usage: `new_pnt = (type *)realloc(old_pnt, new_size)'
The realloc function expands or shrinks the memory allocation in
`old_pnt' to `new_size' number of bytes. Realloc copies as much
of the information from `old_pnt' as it can into the `new_pnt'
space it returns, up to `new_size' bytes. If there is a problem
allocating this memory, 0L will be returned.
If the `old_pnt' is 0L then realloc will do the equivalent of a
`malloc(new_size)'. If `new_size' is 0 and `old_pnt' is not 0L,
then it will do the equivalent of `free(old_pnt)' and will return
0L.
-- Function: void free ( void *PNT )
Usage: `free(pnt)'
The free routine releases allocation in `pnt' which was returned by
malloc, calloc, or realloc back to the heap. This allows other
parts of the program to re-use memory that is not needed anymore.
It guarantees that the process does not grow too big and swallow a
large portion of the system resources.
_WARNING_: there is a quite common myth that all of the space that
is returned by malloc libraries has already been cleared. _Only_ the
`calloc' routine will zero the memory space it returns.
File: dmalloc.info, Node: Features, Next: How It Works, Prev: Allocation Basics, Up: Overview
2.4 General Features of the Library
===================================
The debugging features that are available in this debug malloc library
can be divided into a couple basic classifications:
file and line number information
One of the nice things about a good debugger is its ability to
provide the file and line number of an offending piece of code.
This library attempts to give this functionality with the help of
"cpp", the C preprocessor. *Note Allocation Macros::.
return-address information
To debug calls to the library from external sources (i.e. those
files that could not use the allocation macros), some facilities
have been provided to supply the caller's address. This address,
with the help of a debugger, can help you locate the source of a
problem. *Note Return Address::.
fence-post (i.e. bounds) checking
"Fence-post" memory is the area immediately above or below memory
allocations. It is all too easy to write code that accesses above
or below an allocation - especially when dealing with arrays or
strings. The library can write special values in the areas around
every allocation so it will notice when these areas have been
overwritten. *Note Fence-Post Overruns::.
_NOTE_: The library cannot notice when the program _reads_ from
these areas, only when it writes values. Also, fence-post checking
will increase the amount of memory the program allocates.
heap-constancy verification
The administration of the library is reasonably complex. If any
of the heap-maintenance information is corrupted, the program will
either crash or give unpredictable results.
By enabling heap-consistency checking, the library will run
through its administrative structures to make sure all is in
order. This will mean that problems will be caught faster and
diagnosed better.
The drawback of this is, of course, that the library often takes
quite a long time to do this. It is suitable to enable this only
during development and debugging sessions.
_NOTE_: the heap checking routines cannot guarantee that the tests
will not cause a segmentation-fault if the heap administration
structures are properly (or improperly if you will) overwritten.
In other words, the tests will verify that everything is okay but
may not inform the user of problems in a graceful manner.
logging statistics
One of the reasons why the debug malloc library was initially
developed was to track programs' memory usage - specifically to
locate "memory leaks" which are places where allocated memory is
never getting freed. *Note Memory Leaks::.
The library has a number of logging capabilities that can track
un-freed memory pointers as well as runtime memory usage, memory
transactions, administrative actions, and final statistics.
examining freed memory
Another common problem happens when a program frees a memory
pointer but goes on to use it again by mistake. This can lead to
mysterious crashes and unexplained problems.
To combat this, the library can write special values into a block
of memory after it has been freed. This serves two purposes: it
will make sure that the program will get garbage data if it trying
to access the area again, and it will allow the library to verify
the area later for signs of overwriting.
If any of the above debugging features detect an error, the library
will try to recover. If logging is enabled then an error will be
logged with as much information as possible.
The error messages that the library displays are designed to give the
most information for developers. If the error message is not
understood, then it is most likely just trying to indicate that a part
of the heap has been corrupted.
The library can be configured to quit immediately when an error is
detected and to dump a core file or memory-image. This can be examined
with a debugger to determine the source of the problem. The library
can either stop after dumping core or continue running. *Note Dumping
Core::.
_NOTE_: do not be surprised if the library catches problems with
your system's routines. It took me hours to finally come to the
conclusion that the localtime call, included in SunOS release 4.1,
overwrites one of its fence-post markers.
File: dmalloc.info, Node: How It Works, Prev: Features, Up: Overview
2.5 How the Library Checks Your Program
=======================================
This is one of the newer sections of the library implying that it is
incomplete. If you have any questions or issues that you'd like to see
handled here, please let me know.
The dmalloc library replaces the heap library calls normally found in
your system libraries with its own versions. When you make a call to
malloc (for example), you are calling dmalloc's version of the memory
allocation function. When you allocate memory with these functions, the
dmalloc library keeps track of a number of pieces of debugging
information about your pointer including: where it was allocated,
exactly how much memory was requested, when the call was made, etc..
This information can then be verified when the pointer is freed or
reallocated and the details can be logged on any errors.
Whenever you reallocate or free a memory address, the dmalloc library
always performs a number of checks on the pointer to make sure that it
is valid and has not been corrupted. You can configure the library to
perform additional checks such as detected fence-post writing. The
library can also be configured to overwrite memory with non-zeros (only
if calloc is not called) when it is allocated and erase the memory when
the pointers are freed.
In addition to per-pointer checks, you can configure the library to
perform complete heap checks. These complete checks verify all
internal heap structures and include walking all of the known allocated
pointers to verify each one in turn. You need this level of checking
to find random pointers in your program which got corrupted but that
won't be freed for a while. To turn on these checks, you will need to
enable the `check-heap' debug token. *Note Debug Tokens::. By default
this will cause the heap to be fully checked each and every time
dmalloc is called whether it is a malloc, free, realloc, or another
dmalloc overloaded function.
Performing a full heap check can take a good bit of CPU and it may be
that you will want to run it sporadically. This can be accomplished in
a couple different ways including the '-i' interval argument to the
dmalloc utility. *Note Dmalloc Program::. This will cause the check to
be run every N-th time. For instance, 'dmalloc -i 3' will cause the
heap to be checked before every 3rd call to a memory function. Values
of 100 or even 1000 for high memory usage programs are more useful than
smaller ones.
You can also cause the program to start doing detailed heap checking
after a certain point. For instance, with 'dmalloc -s 1000' option, you
can tell the dmalloc library to enable the heap checks after the 1000th
memory call. Examine the dmalloc log file produced and use the
iteration count if you have `LOG_ITERATION_COUNT' enabled in your
`settings.h' file.
The start option can also have the format `file:line'. For
instance, if it is set to `dmalloc_t.c:126', dmalloc will start
checking the heap after it sees a dmalloc call from the `dmalloc_t.c'
file, line number 126. If you use `dmalloc_t.c:0', with a 0 line
number, then dmalloc will start checking the heap after it sees a call
from anywhere in the `dmalloc_t.c' file.
File: dmalloc.info, Node: Programming, Next: Dmalloc Program, Prev: Overview, Up: Top
3 How to Program with the Library
*********************************
* Menu:
* Allocation Macros:: Macros providing file and line information.
* Return Address:: Getting caller address information.
* Argument Checking:: Checking of function arguments.
* Dumping Core:: Generating a core file on errors for debugging.
* Extensions:: Additional non-standard routines.
* Error Codes:: Description of the internal error numbers.
* Disabling the Library:: How to disable the library.
* Using With C++:: Using the library with C++.
* Using With a Debugger:: Using a debugger with the library.
* Using With Threads:: Using the library with a thread package.
* Using With Cygwin:: Using the library with Cygwin environment.
* Debugging A Server:: Debugging memory in a server or cgi-bin process.
* Logfile Details:: Explanation of the Logfile Output.
* Other Hints:: Various other hints that may help.
File: dmalloc.info, Node: Allocation Macros, Next: Return Address, Prev: Programming, Up: Programming
3.1 Macros Providing File and Line Information
==============================================
By including `dmalloc.h' in your C files, your calls to malloc, calloc,
realloc, recalloc, memalign, valloc, strdup, and free are replaced with
calls to _dmalloc_malloc, _dmalloc_realloc, and _dmalloc_free with
various flags. Additionally the library replaces calls to xmalloc,
xcalloc, xrealloc, xrecalloc, xmemalign, xvalloc, xstrdup, and xfree
with associated calls.
These macros use the c-preprocessor `__FILE__' and `__LINE__' macros
which get replaced at compilation time with the current file and
line-number of the source code in question. The routines use this
information to produce verbose reports on memory problems.
not freed: '0x38410' (22 bytes) from 'dmalloc_t.c:92'
This line from a log file shows that memory was not freed from file
`dmalloc_t.c' line 92. *Note Memory Leaks::.
You may notice some non standard memory allocation functions in the
above list. Recalloc is a routine like realloc that reallocates
previously allocated memory to a new size. If the new memory size is
larger than the old, recalloc initializes the new space to all zeros.
This may or may not be supported natively by your operating system.
Memalign is like malloc but should insure that the returned pointer is
aligned to a certain number of specified bytes. Currently, the memalign
function is not supported by the library. It defaults to returning
possibly non-aligned memory for alignment values less than a block-size.
Valloc is like malloc but insures that the returned pointer will be
aligned to a page boundary. This may or may not be supported natively
by your operating system but is fully supported by the library. Strdup
is a string duplicating routine which takes in a null terminated string
pointer and returns an allocated copy of the string that will need to be
passed to free later to deallocate.
The X versions of the standard memory functions (xmalloc, xfree,
etc.) will print out an error message to standard error and will stop
if the library is unable to allocate any additional memory. It is
useful to use these routines instead of checking everywhere in your
program for allocation routines returning NULL pointers.
_WARNING_: If you are including the `dmalloc.h' file in your
sources, it is recommended that it be at the end of your include file
list because dmalloc uses macros and may try to change declarations of
the malloc functions if they come after it.
File: dmalloc.info, Node: Return Address, Next: Argument Checking, Prev: Allocation Macros, Up: Programming
3.2 Getting Caller Address Information
======================================
Even though the allocation macros can provide file/line information for
some of your code, there are still modules which either you can't
include `dmalloc.h' (such as library routines) or you just don't want
to. You can still get information about the routines that call dmalloc
function from the return-address information. To accomplish this, you
must be using this library on one of the supported
architecture/compilers. *Note Portability::.
The library attempts to use some assembly hacks to get the
return-address or the address of the line that called the dmalloc
function. If you have unfreed memory that does not have associated file
and line information, you might see the following non-freed memory
messages.
not freed: '0x38410' (22 bytes) from 'ra=0xdd2c'
not freed: '0x38600' (10232 bytes) from 'ra=0x10234d'
not freed: '0x38220' (137 bytes) from 'ra=0x82cc'
With the help of a debugger, these return-addresses (or ra) can then
be identified. I've provided a `ra_info.pl' perl script in the
`contrib/' directory with the dmalloc sources which seems to work well
with gdb. You can also use manual methods for gdb to find the
return-address location. *Note Translate Return Addresses::.
File: dmalloc.info, Node: Argument Checking, Next: Dumping Core, Prev: Return Address, Up: Programming
3.3 Checking of Function Arguments
==================================
One potential problem with the library and its multitude of checks and
diagnoses is that they only get performed when a dmalloc function is
called. One solution this is to include `dmalloc.h' and compile your
source code with the `DMALLOC_FUNC_CHECK' flag defined and enable the
`check-funcs' token. *Note Debug Tokens::.
cc -DDMALLOC -DDMALLOC_FUNC_CHECK file.c
_NOTE_: Once you have compiled your source with DMALLOC_FUNC_CHECK
enabled, you will have to recompile with it off to disconnect the
library. *Note Disabling the Library::.
_WARNING_: You should be sure to have `dmalloc.h' included at the
end of your include file list because dmalloc uses macros and may try
to change declarations of the checked functions if they come after it.
When this is defined dmalloc will override a number of functions and
will insert a routine which knows how to check its own arguments and
then call the real function. Dmalloc can check such functions as
`bcopy', `index', `strcat', and `strcasecmp'. For the full list see
the end of `dmalloc.h'.
When you call `strlen', for instance, dmalloc will make sure the
string argument's fence-post areas have not been overwritten, its file
and line number locations are good, etc. With `bcopy', dmalloc will
make sure that the destination string has enough space to store the
number of bytes specified.
For all of the arguments checked, if the pointer is not in the heap
then it is ignored since dmalloc does not know anything about it.
File: dmalloc.info, Node: Dumping Core, Next: Extensions, Prev: Argument Checking, Up: Programming
3.4 Generating a Core File on Errors
====================================
If the `error-abort' debug token has been enabled, when the library
detects any problems with the heap memory, it will immediately attempt
to dump a core file. *Note Debug Tokens::. Core files are a complete
copy of the program and it's state and can be used by a debugger to see
specifically what is going on when the error occurred. *Note Using
With a Debugger::. By default, the low, medium, and high arguments to
the library utility enable the `error-abort' token. You can disable
this feature by entering `dmalloc -m error-abort' (-m for minus) to
remove the `error-abort' token and your program will just log errors
and continue. You can also use the `error-dump' token which tries to
dump core when it sees an error but still continue running. *Note
Debug Tokens::.
When a program dumps core, the system writes the program and all of
its memory to a file on disk usually named `core'. If your program is
called `foo' then your system may dump core as `foo.core'. If you are
not getting a `core' file, make sure that your program has not changed
to a new directory meaning that it may have written the core file in a
different location. Also insure that your program has write privileges
over the directory that it is in otherwise it will not be able to dump
a core file. Core dumps are often security problems since they contain
all program memory so systems often block their being produced. You
will want to check your user and system's core dump size ulimit
settings.
The library by default uses the `abort' function to dump core which
may or may not work depending on your operating system. If the
following program does not dump core then this may be the problem. See
`KILL_PROCESS' definition in `settings.dist'.
main()
{
abort();
}
If `abort' does work then you may want to try the following setting
in `settings.dist'. This code tries to generate a segmentation fault
by dereferencing a `NULL' pointer.
#define KILL_PROCESS { int *_int_p = 0L; *_int_p = 1; }
File: dmalloc.info, Node: Extensions, Next: Error Codes, Prev: Dumping Core, Up: Programming
3.5 Additional Non-standard Routines
====================================
The library has a number of variables that are not a standard part of
most malloc libraries:
-- Variable: int dmalloc_errno
This variable stores the internal dmalloc library error number
like errno does for the system calls. It can be passed to
`dmalloc_strerror()' (see below) to get a string version of the
error. It will have a value of zero if the library has not
detected any problems.
-- Variable: char* dmalloc_logpath
This variable can be used to set the dmalloc log filename. The env
variable `DMALLOC_LOGFILE' overrides this variable.
Additionally the library provides a number of non-standard malloc
routines:
-- Function: void dmalloc_shutdown ( void )
This function shuts the library down and logs the final statistics
and information especially the non-freed memory pointers. The
library has code to support auto-shutdown if your system has the
`on_exit()' call, `atexit()' call, or compiler destructor support
(see `conf.h'). If you do not have these, then `dmalloc_shutdown'
should be called right before `exit()' or as the last function in
`main()'.
main()
{
...
dmalloc_shutdown();
exit(0);
}
-- Function: int dmalloc_verify ( char * PNT )
This function verifies individual memory pointers that are suspect
of memory problems. To check the entire heap pass in a NULL or 0
pointer. The routine returns DMALLOC_VERIFY_ERROR or
DMALLOC_VERIFY_NOERROR.
_NOTE_: `dmalloc_verify()' can only check the heap with the
functions that have been enabled. For example, if fence-post
checking is not enabled, `dmalloc_verify()' cannot check the
fence-post areas in the heap.
-- Function: unsigned-int dmalloc_debug ( const unsigned int FLAGS )
This routine sets the debug functionality flags and returns the
previous flag value. It is helpful in server or cgi-bin programs
where environmental variables cannot be used. *Note Debugging A
Server::. For instance, if debugging should never be enabled for a
program, a call to `dmalloc_debug(0)' as the first call in
`main()' will disable all the memory debugging from that point on.
_NOTE_: you cannot add or remove certain flags such as signal
handlers since they are setup at initialization time only.
_NOTE_: you can also use `dmalloc_debug_setup' below.
-- Function: unsigned-int dmalloc_debug_current ( void )
This routine returns the current debug functionality value value.
This allows you to save a copy of the debug dmalloc settings to be
changed and then restored later.
-- Function: void dmalloc_debug_setup ( const char * OPTIONS_STR )
This routine sets the global debugging functionality as an option
string. Normally this would be passed in in the DMALLOC_OPTIONS
environmental variable. This is here to override the env or for
circumstances where modifying the environment is not possible or
does not apply such as servers or cgi-bin programs. *Note
Debugging A Server::.
Some examples:
/*
* debug tokens high, threaded lock-on at 20,
* log to dmalloc.%p (pid)
*/
dmalloc_debug_setup("debug=0x4f46d03,lockon=20,log=dmalloc.%p");
/*
* turn on some debug tokens directly and log to the
* file 'logfile'
*/
dmalloc_debug_setup(
"log-stats,log-non-free,check-fence,log=logfile");
-- Function: int dmalloc_examine ( const DMALLOC_PNT PNT, DMALLOC_SIZE
* USER_SIZE_P, DMALLOC_SIZE * TOTAL_SIZE_P, char ** FILE_P,
int * LINE_P, DMALLOC_PNT * RET_ADDR_P, unsigned long *
USER_MARK_P, unsigned long * SEEN_P )
This function returns the size of a pointer's allocation as well
as the total size given including administrative overhead, file
and line or the return-address from where it was allocated, the
last pointer when the pointer was "used", and the number of times
the pointer has been "seen". It will return DMALLOC_NOERROR or
DMALLOC_ERROR depending on whether pnt is good or not.
_NOTE_: This function is _certainly_ not provided by most if not
all other malloc libraries.
-- Function: void dmalloc_track ( const dmalloc_track_t TRACK_FUNC )
Register an allocation tracking function which will be called each
time an allocation occurs. Pass in NULL to disable. To take a
look at what information is provided, see the dmalloc_track_t
function typedef in dmalloc.h.
-- Function: unsigned-long dmalloc_mark ( void )
Return to the caller the current "mark" which can be used later to
log the pointers which have changed since this mark with the
`dmalloc_log_changed' function. Multiple marks can be saved and
used.
This is very useful when using the library with a server which does
not exit. You can then save a mark before a transaction or event
happens and then check to see what has changed using the
`dmalloc_log_changed' function below. *Note Debugging A Server::.
If you `LOG_ITERATION' enabled in your `settings.h' file then the
entries in the log file will be prepended with the number of memory
transactions that the library has handled so far. You can also
enable `LOG_PNT_ITERATION' in `settings.h' to store the memory
transaction number with each pointer.
-- Function: unsigned-long dmalloc_memory_allocated ( void )
Return to the caller the total number of bytes that have been
allocated by the library. This is not the current in use but the
total number of bytes returned by allocation functions.
-- Function: unsigned-int dmalloc_page_size ( void )
Return to the caller the memory page-size being used by the
library. This should be the same value as the one returned by the
`getpagesize()' function, if available.
-- Function: unsigned-long dmalloc_count_changed ( const unsigned long
MARK, const int NOT_FREED_B, const int FREE_B )
Count the pointers that have changed since the mark which was
returned by `dmalloc_mark'. If `not_freed_b' is set to non-0 then
count the pointers that have not been freed. If `free_b' is set
to non-0 then count the pointers that have been freed.
This can be used in conjunction with the `dmalloc_mark()' function
to help servers which never exit ensure that transactions or
events are not leaking memory. *Note Debugging A Server::.
unsigned long mark = dmalloc_mark() ;
...
assert(dmalloc_count_changed(mark, 1, 0) == 0) ;
-- Function: void dmalloc_log_stats ( void )
This routine outputs the current dmalloc statistics to the log
file.
-- Function: void dmalloc_log_unfreed ( void )
This function logs the unfreed-memory information to the log file.
This is also useful to log the currently allocated points to the
log file to be compared against another dump later on.
-- Function: void dmalloc_log_changed ( const unsigned long MARK,
const int NOT_FREED_B, const int FREED_B, const int DETAILS_B
)
Log the pointers that have changed since the mark which was
returned by `dmalloc_mark'. If `not_freed_b' is set to non-0 then
log the pointers that have not been freed. If `free_b' is set to
non-0 then log the pointers that have been freed. If `details_b'
set to non-0 then log the individual pointers that have changed
otherwise just log the summaries.
This can be used in conjunction with the `dmalloc_mark()' function
to help servers which never exit find transactions or events which
are leaking memory. *Note Debugging A Server::.
-- Function: void dmalloc_vmessage ( const char * FORMAT, va_list ARGS
)
Write a message into the dmalloc logfile using vprintf-like
arguments.
-- Function: void dmalloc_message ( const char * FORMAT, ... )
Write a message into the dmalloc logfile using printf-like
arguments.
-- Function: void dmalloc_get_stats ( DMALLOC_PNT * HEAP_LOW_P,
DMALLOC_PNT * HEAP_HIGH_P, unsigned long * TOTAL_SPACE_P,
unsigned long * USER_SPACE_P, unsigned long *
CURRENT_ALLOCATED_P, unsigned long * CURRENT_PNT_NP, unsigned
long * MAX_ALLOCATED_P, unsigned long * MAX_PNT_NP, unsigned
long * MAX_ONE_P)
This function return a number of statistics about the current heap.
The pointers `heap_low_p' and `heap_high_p' will be set to the low
and high spots in the heap. `total_space_p' will be set to the
total space in the heap including user space, administrative
space, and overhead. `user_space_p' will be set to the space
given to the user process (allocated and free space).
`current_allocated_p' will be set to the current allocated space
given to the user process. `current_pnt_np' will be set to the
current number of pointers allocated by the user process.
`max_allocated_p' will be set to the maximum allocated space given
to the user process. `max_pnt_np' will be set to the maximum
number of pointers allocated by the user process. `max_on_p' will
be set to the maximum space allocated with one call by the user
process.
-- Function: const-char* dmalloc_strerror ( const int ERROR_NUMBER )
This function returns the string representation of the error value
in `error_number' (which probably should be dmalloc_errno). This
allows the logging of more verbose memory error messages.
You can also display the string representation of an error value
by a call to the `dmalloc' program with a `-e #' option. *Note
Dmalloc Program::.
File: dmalloc.info, Node: Error Codes, Next: Disabling the Library, Prev: Extensions, Up: Programming
3.6 Description of the Internal Error Codes
===========================================
The following error codes are defined in `error_val.h'. They are used
by the library to indicate a detected problem. They can be caused by
the user (`ERROR_TOO_BIG') or can indicate an internal library problem
(`ERROR_SLOT_CORRUPT'). The `dmalloc' utility can give you the string
version of the error with the `-e' argument:
$ dmalloc -e 60
dmalloc: dmalloc_errno value '60' =
'pointer is not on block boundary'
Here are the error codes set by the library. They are non
contiguous on purpose because I add and delete codes all of the time
and there are sections for various error-code types.
`1 (ERROR_NONE) no error'
No error. It is good coding practice to set the no-error code to
be non-0 value because it forces you to set it explicitly.
`2 (INVALID_ERROR)'
Invalid error number. If the library outputs this error then your
dmalloc utility may be out of date with the library you linked
against. This will be returned with all error codes not listed
here.
`10 (ERROR_BAD_SETUP) initialization and setup failed'
Bad setup value. This is currently unused but it is intended to
report on invalid setup configuration information.