Re: [Iverilog-devel] Fopen the same file twice for writeing?

[Stephen W. <st...@ic...>]

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The behavior you get will depend on the scheduling order of the
initial statements, and to a lesser degree on the operating system.
Icarus Verilog uses fopen(<P>,"w") to open MCD files, and in your
case, opening twice, the second open will truncate the first.

It appears that VCS and ncsim agree with Icarus Verilog, at least
in the broader sense. Modelsim seems to be making some special effort
to detect that you opened the file twice and combine file descriptors,
which may make a small bit of sense given that mcd descriptors are
precious. But really, that strikes me as a lot of effort to support
a bad input.

I think this situation is (and should be) left unspecified. Just
don't do that!-)

Andrei Purdea wrote:
> Hello!
> I have found a weird modelsim behavior where if you open the same
> filename twice with the one-parameter (multichannel descriptor) $fopen
> then one of the fopens will not overwrite the other one, but instead
> both outputs end up in the output file.
> 
> Iverilog behaves the way i'd expect it to.
> 
> Do other simulators behave like modelsim?
> 
> (result of the attached .v file)
> iverilog:(all versions)
> 
> andrew@charon:~$ cat test.txt; rm test.txt
> second
> second after first is closed
> andrew@charon:~$ cat test.txtb; rm test.txtb
> second
> second after first is closed
> andrew@charon:~$ cat test.txtc; rm test.txtc
> first
> 
> 
> modelsim:
> 
> andrew@charon:~$ cat test.txt; rm test.txt
> first
> second
> andrew@charon:~$ cat test.txtb; rm test.txtb
> second
> second after first is closed
> andrew@charon:~$ cat test.txtc; rm test.txtc
> first
> second


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Steve Williams                "The woods are lovely, dark and deep.
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