From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mark Mitchell <mark@codesourcery.com>
To: law@cygnus.com
Cc: robertlipe@usa.net, ghazi@caip.rutgers.edu, egcs@egcs.cygnus.com
Subject: Re: Should we create an attribute malloc for supposed aliasbenefits? 
Date: Thu, 30 Sep 1999 18:02:00 -0000
Message-ID: <19990907171407X.mitchell@codesourcery.com>
References: <19990906170243.C11191@rjlhome.sco.com> <22850.936688821@upchuck.cygnus.com>
X-SW-Source: 1999-09n/msg00252.html
Message-ID: <19990930180200.esRIhbThiWaKuvNxUCTtPMSHlzpMLKubi8Ky9ZFUdYQ@z>

>>>>> "Jeffrey" == Jeffrey A Law <law@cygnus.com> writes:

    Jeffrey> Mark as the resident expert, can "restrict" be used to
    Jeffrey> tell the aliasing code that the return value from certain
    Jeffrey> functions can never alias anything else in the program?

I think the answer is "no, but that's OK".  For example, the following
code is legal C9X:

  int *restrict rp1;

  int *restrict f () {
    return rp1;
  }

  void f()
  {
    int *restrict rp2 = f();
  }

If GCC can't tell `f' from `malloc', then it must worry that the
storage returned by `malloc' is actually the same memory pointed to by
`rp1'.  But, C9X forbids using `rp1' to access memory while `rp2' is
in (dynamic) scope.

Making sense?  C9X committee members?

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com