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Re: fread a file of unknown size

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Keith Thompson <kst-u@mib.org> wrote:

(snip, I wrote)

>> The biggest problem I remember with gnu utilities is that they would
>> use 0 as an argument to a function expecting (char *). When I complained
>> to the gnu people, they had some comment about systems having different
>> sized (int) and (char*) not being supported.
 
> I don't suppose you have an example?
 
> If there's a visible prototype, passing 0 to a non-variadic function
> expecting a char* is not a problem.  It will be implicitly converted to
> char*, and converting a constant 0 to a pointer type yields a null
> pointer.  (Personally I'd use NULL or (char*)NULL just for the sake of
> clarity.)

That was in 1990.  I was running MSC 6.0 (the first with OS/2 support)
and large mode, so pointers were segment selector/offset in 32 bits,
and int at 16 bits. 
 
> Passing 0 to a function expecting a char* either when there's no visible
> prototype, or when it corresponds to the ", ..." in a variadic function,
> does have undefined behavior.  It can break if char* and int are of
> different sizes, if a null pointer is not represented as all-bits-zero,
> if int and char* are passed as arguments using different mechanisms, or
> for any other conceivable reason.

Microsoft had ANSI C support around 1989, but I don't know how fast
people went back and added the prototypes.  I do know that it wouldn't
run until I put in (char*)0 for the 0 in the right places.

-- glen

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fread a file of unknown size ruben safir <ruben@mrbrklyn.com> - 2015-03-08 14:47 -0400
  Re: fread a file of unknown size Richard Heathfield <rjh@cpax.org.uk> - 2015-03-08 18:59 +0000
    Re: fread a file of unknown size James Kuyper <jameskuyper@verizon.net> - 2015-03-08 18:21 -0400
      Re: fread a file of unknown size Keith Thompson <kst-u@mib.org> - 2015-03-08 18:43 -0700
    Re: fread a file of unknown size fmassei@gmail.com - 2015-03-08 15:41 -0700
      Re: fread a file of unknown size raltbos@xs4all.nl (Richard Bos) - 2015-03-10 16:04 +0000
    Re: fread a file of unknown size Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-03-08 18:44 -0400
  Re: fread a file of unknown size jacob navia <jacob@spamsink.net> - 2015-03-08 20:32 +0100
  Re: fread a file of unknown size Keith Thompson <kst-u@mib.org> - 2015-03-08 12:48 -0700
  Re: fread a file of unknown size glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-03-08 23:39 +0000
    Re: fread a file of unknown size James Kuyper <jameskuyper@verizon.net> - 2015-03-08 20:40 -0400
      Re: fread a file of unknown size glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-03-09 01:24 +0000
        Re: fread a file of unknown size Keith Thompson <kst-u@mib.org> - 2015-03-09 07:53 -0700
          Re: fread a file of unknown size glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-03-09 17:36 +0000
            Re: fread a file of unknown size Keith Thompson <kst-u@mib.org> - 2015-03-09 10:44 -0700
              Re: fread a file of unknown size glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-03-09 20:07 +0000

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