[petsc-dev] [petsc-users] PetscPrintf

[Junchao Zhang]

On Thu, Apr 12, 2018 at 9:48 AM, Smith, Barry F. <bsmith at mcs.anl.gov> wrote:

>
>
> > On Apr 12, 2018, at 3:59 AM, Patrick Sanan <patrick.sanan at gmail.com>
> wrote:
> >
> > I also happened to stumble across this yesterday. Is the length
> restriction for the default printer (l assume from the array of 8*1024
> chars in PetscVFPrintfDefault() ) intended behavior to be documented, or a
> bug to be fixed?
>
>      You could call it either. My problems are
>
> 1) that given a format string I don't know in advance how much work space
> is needed so cannot accurately malloc, for sure, enough space
>
> 2) since this can be called in an error handler I really don't want it
> calling malloc().
>
PetscVSNPrintf does still contain a malloc "122  ierr      =
PetscMalloc1(oldLength, &newformat);CHKERRQ(ierr);"
Also, vsnprintf returns "the number of characters that would have been
written if n had been sufficiently large". I don't know why you void'ed it.
We can not make the 8K chars a requirement since users don't know how many
chars they want to print upfront.
Anyway, crash is better than silent errors.

>
>    Hence it lives in this limbo. I don't even know a way to add a good
> error checking that detects if the buffer is long enough. All in all it is
> bad ugly code, any suggestions on improvements would be appreciated.
>
>    Barry
>
> >
> > 2018-04-12 2:16 GMT+02:00 Rongliang Chen <rongliang.chan at gmail.com>:
> > Thanks Barry. I found petsc-3.6 and older versions did not have this
> restriction.
> >
> > Best,
> > Rongliang
> >
> >
> > On 04/12/2018 07:22 AM, Smith, Barry F. wrote:
> >    Yes, PetscPrintf() and related functions have a maximum string length
> of about 8000 characters.
> >
> >     Barry
> >
> >
> > On Apr 11, 2018, at 6:17 PM, Rongliang Chen <rongliang.chan at gmail.com>
> wrote:
> >
> > Dear All,
> >
> >
> > When I tried to print a long string using PetscPrintf() I found that it
> truncated the string. Attached is a simple example for this (run with
> single processor). I used PetscPrintf() and printf() to print the same
> string and the printf() seems OK. I am using petsc-3.8.4.
> >
> >
> > Best,
> >
> > Rongliang
> >
> > <ex111.c>
> >
> >
> >
>
>
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