malloc_cv(3)

NAME
     malloc, free, realloc, calloc, memalign, valloc, cvmalloc_error -
     WorkShop memory allocation library

SYNOPSIS
     #include <stdlib.h>

     void *malloc (size_t size);

     void free (void *ptr);

     void *realloc (void *ptr, size_t size);

     void *calloc (size_t nelem, size_t elsize);

     void *memalign (size_t alignment, size_t size);

     void *valloc (size_t size);

     void cvmalloc_error (char *message);

DESCRIPTION
     The WorkShop Performance Tools contain a malloc library, -lmalloc_cv,
     which provides tracing and error detection around calls to the various
     malloc routines.

     The library provides an intercept layer for calls to malloc, free,
     realloc, memalign, and valloc; the intercept allows tracing of all calls
     with the WorkShop performance tools.

     Calls to malloc, free, and realloc are passed through to whatever memory
     allocation library the program is linked with.  Calls to calloc are
     actually not intercepted, but rely on the underlying calloc to call
     malloc to get the space allocated.  Calls to memalign are implemented by
     allocating a block large enough to hold the aligned area asked for by the
     user, as well as a guard area that holds a flag indicating that the user
     block was obtained through memalign, and the address of the larger block.
     Calls to valloc are translated into a call to getpagesize, followed by a
     memalign call.

     The last function, cvmalloc_error is called whenever any error is
     detected; a debugger trap may be placed at exit from that routine to
     interactively examine malloc errors.

MALLOC TRACING
     The library provides for tracing of all calls to any of the entry points
     listed above, as well as any of the errors listed below.  The trace is
     normally captured using a WorkShop performance experiment.  It may be
     written in ASCII to stderr by enabling the environment variable
     MALLOC_TRACING, although this typically produces a great deal of output.

ERROR DETECTION
     The library will detect some errors under all conditions, and others if
     MALLOC_FASTCHK error detection is enabled.  All errors pass through the
     routine cvmalloc_error and a trap can be placed at the exit from that
     routine to catch the problem.  Errors are also traced.

     The errors that are always detected are:
          malloc call failing (returning NULL).
          realloc call failing (returning NULL).
          realloc call with an address outside the range of heap addresses
          returned by malloc or memalign.
          memalign call with an improper alignment.
          free call with an address that is improperly aligned.
          free call with an address outside the range of heap addresses
          returned by malloc or memalign.

     If MALLOC_FASTCHK is enabled, the library will also detect:
          free or realloc calls where the words prior to the user block have
          been corrupted.
          free or realloc calls where the words following the user block have
          been corrupted.
          free or realloc calls where the address is that of a block that has
          already been freed.  This error may not always be detected if the
          area around the block is reallocated after it was first freed.

     The behavior of the library is governed by various environment variables:

     MALLOC_VERBOSE n
          (where n is an integer) controls printing of messages from the
          library.  If n = 0, messages are printed to stderr ony when an error
          occurs.  If n = 1 (the default), a messages is printed during
          initialization, so that the user can tell that the library was
          properly included in the application.  If n = 2 or greater, detailed
          information about all traced events, including the callstack at the
          time the error was detected, is printed.  This option is not
          normally used by the end user, as it can produce a huge vloume of
          output.

     MALLOC_TRACING
          enables tracing of all calls through the library.  Tracing is
          normally done in the course of a performance experiment; the
          variable need not be set in such cases, as the running of the
          experiment will automatically enable it.  If the option is enabled
          when the program is run independently, and MALLOC_VERBOSE is set to
          2 or greater, the trace events and program call stacks will be
          written to stderr.

     MALLOC_FASTCHK
          enables corruption detection for library calls.  Corruption
          detection is done by allocating a space larger than the requested
          area, and putting specific patterns in front of and behind the area
          returned to the caller.  When free is called, the patterns are
          checked, and if the area was overwritten, an error message is
          printed using an internal call to the routine cvmalloc_error. Under
          the debugger, a trap may be set at exit from this routine to catch
          the program at the error.

     MALLOC_FULLWARN
          enables detection of some calls that are not strictly errors, but
          represent sloppy programming, including free(NULL), malloc(0), and
          realloc(ptr,0).

     MALLOC_MAXMALLOC n
          (where n is an integer, in any base) sets a maximum size for any
          malloc or realloc or memalign allocation.  Any request exceeding
          that size will be flagged as an error, and return a NULL pointer.

     MALLOC_NO_REUSE
          specifies that no area that has been freed will be reused.  With
          this option enabled, no actual free calls are really made, and the
          process space and swap requirements can grow quite large.  If
          MALLOC_FASTCHK is not enabled, any space that is freed by a realloc
          may or may not get reused; if MALLOC_FASTCHK is enabled, such space
          will not be reused.

     MALLOC_CLEAR_FREE
          will clear the data upon any free call.  It will only work if
          MALLOC_FASTCHK is also enabled.

     MALLOC_CLEAR_FREE_PATTERN <pattern>
          specifies a pattern to clear the data if MALLOC_CLEAR_FREE is
          enabled.  The default pattern is 0xcafebeef for the 32-bit version,
          and 0xcafebeefcafebeef for the 64-bit versions.  Only full words
          (double words for 64-bits) are cleared to the pattern.

     MALLOC_CLEAR_MALLOC
          will clear the memory area upon each allocation.  It also requires
          MALLOC_FASTCHK be enabled.

     MALLOC_CLEAR_MALLOC_PATTERN <pattern>
          specifies a pattern to clear the data if MALLOC_CLEAR_MALLOC is
          enabled.  The default pattern is 0xfacebeef for the 32-bit version,
          and 0xfacebeeffacebeef for the 64-bit versions.  Only full words
          (double words for 64-bits) are cleared to the pattern.

SEE ALSO
     malloc(3C), malloc(3X), cvspeed(1), cvperf(1).

DIAGNOSTICS
     As ouput from the library routines.