Is malloc reentrant

[Joerg Lehners]

In comp.sys.sun you write:
>Is malloc guaranteed to be reentrant, if not is it reentrant on any
>systems?

I think malloc can't be reentrant because it modifies a global resource
(the heap). I cannot imagine an algorithmn that modifies a global resource
without using some kind of locking.  Implementing malloc (and friends
free, realloc, calloc) with a locking mechanismn is useless in single
threaded application: another call to malloc from e.g. a signal handler
would block the whole application, if the signal handler was called when
the process was in the middle of malloc.  Whereas malloc with a locking
mechanism would be sensefull in mutli threaded applications (like the
light weight prcess of SunOS4.x)

  Joerg Lehners

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