[petsc-dev] need C++ expert help

[Barry Smith]

   The problem is ssize_t is not portable to Microsoft.


> On Sep 13, 2016, at 3:05 PM, Munson, Todd <tmunson at mcs.anl.gov> wrote:
> 
> 
> The write statement return type is ssize_t.  For whatever reason its a signed type
> because it can return -1 on error.
> 
> I would suggest using the ssize_t type for both and changing the "!=" to a "<"
> which will abort if write either returns a negative or the number of bytes 
> written is not correct.
> 
> Note: you will have problems if (ssize_t) (m*n*sizeof(double)) is negative 
> though, but that can be checked as well.
> 
> Todd.
> 
>> On Sep 13, 2016, at 2:50 PM, Satish Balay <balay at mcs.anl.gov> wrote:
>> 
>> This works..
>> 
>> Satish
>> 
>> ---------
>> 
>> diff --git a/src/mat/examples/tests/ex45.c b/src/mat/examples/tests/ex45.c
>> index 63d0a30..37f68e3 100644
>> --- a/src/mat/examples/tests/ex45.c
>> +++ b/src/mat/examples/tests/ex45.c
>> @@ -72,7 +72,7 @@ void Store2DArray(int m,int n,double *a,const char *filename,int *fdd)
>>      vals[i+m*j] = a[j+i*n];
>>    }
>>  }
>> -  if (write(fd,vals,m*n*sizeof(double)) != ((unsigned int) (m*n))*sizeof(double)) abort();
>> +  if ((size_t)write(fd,vals,m*n*sizeof(double)) != (size_t)(m*n*sizeof(double))) abort();
>>  free(vals);
>> 
>> }
>> @@ -94,7 +94,7 @@ void Store1DArray(int m,double *a,const char *filename,int *fdd)
>>  }
>>  if (write(fd,&classid,sizeof(int)) != sizeof(int)) abort();
>>  if (write(fd,&m,sizeof(int)) != sizeof(int)) abort();
>> -  if (write(fd,a,m*sizeof(double)) != ((unsigned int)m)*sizeof(double)) abort();
>> +  if ((size_t)write(fd,a,m*sizeof(double)) != (size_t)(m*sizeof(double))) abort();
>> }
>> 
>> 
>> On Tue, 13 Sep 2016, Satish Balay wrote:
>> 
>>> I would tink if its typecast to same type - comparision would work..
>>> 
>>> if ((ssize_t)write(fd,vals,m*n*sizeof(double)) != (ssize_t)(m*n*sizeof(double))) abort();
>>> 
>>> I'll give this a try...
>>> 
>>> Satish
>>> 
>>> On Tue, 13 Sep 2016, Barry Smith wrote:
>>> 
>>>> 
>>>>  I need help from someone who knows the subtleties of c++.  We have a PETSc example that always compiles fine with C but generates annoying warnings with C++. I've tried many different variants to eliminate the warnings with no luck
>>>> 
>>>>  Any help is appreciated.
>>>> 
>>>>   Barry
>>>> 
>>>> 
>>>> mpicxx -o ex45.o -c -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -fvisibility=hidden -g -O   -fPIC    -I/sandbox/petsc/petsc.clone-3/include -I/sandbox/petsc/petsc.clone-3/arch-linux-opt-cxx-quad/include -I/usr/include/mpich2    `pwd`/ex45.c
>>>> /sandbox/petsc/petsc.clone-3/src/mat/examples/tests/ex45.c: In function ‘void Store2DArray(int, int, double*, const char*, int*)’:
>>>> /sandbox/petsc/petsc.clone-3/src/mat/examples/tests/ex45.c:75:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
>>>>  if (write(fd,vals,m*n*sizeof(double)) != ((unsigned int) (m*n))*sizeof(double)) abort();
>>>>                                        ^
>>>> /sandbox/petsc/petsc.clone-3/src/mat/examples/tests/ex45.c: In function ‘void Store1DArray(int, double*, const char*, int*)’:
>>>> /sandbox/petsc/petsc.clone-3/src/mat/examples/tests/ex45.c:97:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
>>>>  if (write(fd,a,m*sizeof(double)) != ((unsigned int)m)*sizeof(double)) abort();
>>>> 
>>>> 
>>>> It can be found here ftp://ftp.mcs.anl.gov/pub/petsc/nightlylogs/archive/2016/09/13/examples_next_arch-linux-opt-cxx-quad_grind.log
>>> 
>