How about the logic of this analysis? 1. We are trying to use the same functions (in particular, PetscVFPrintf) for two purposes: a. printing error messages (don't want to malloc) b. use by public API printing functions (don't want length restrictions) 2. Right now, PetscVFPrintf works fine for a but not for b. We could make it work for b and not for a by malloc'ing a longer string. 3. Printing from error handlers happens through PetscErrorPrintf (default : http://www.mcs.anl.gov/petsc/petsc-dev/src/sys/error/errtrace.c.html#PetscEr... ), so if there's a special requirement for printing error messages, we can impose it here. A solution could then be something which skips the malloc only when printing an error, e.g. 1. Add an argument to PetscVFPrintf (say "PetscBool noMalloc") [1] 2. API (PetscPrintf(), etc.) functions use noMalloc = PETSC_FALSE 3. error functions (PetscErrorPrintf() ) functions use noMalloc = PETSC_TRUE [1] And probably do the same thing in PetscVSNPrintf since, as Dr. Zhang pointed out, this could also call malloc while handling an error, if the string was long enough 2018-04-13 15:59 GMT+02:00 Junchao Zhang <[email protected]>:

On Thu, Apr 12, 2018 at 9:48 AM, Smith, Barry F. <[email protected]> wrote:

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On Apr 12, 2018, at 3:59 AM, Patrick Sanan <[email protected]> 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.

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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

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2018-04-12 2:16 GMT+02:00 Rongliang Chen <[email protected]>: Thanks Barry. I found petsc-3.6 and older versions did not have this

restriction.

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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.

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Barry

On Apr 11, 2018, at 6:17 PM, Rongliang Chen <[email protected]>

wrote:

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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.

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Best,

Rongliang

<ex111.c>