I think the key is your observation:
char buffer[20];
inst_var.getVar(buffer);
to
char * buffer;
inst_var.getVar(&buffer);
If the variable is actually of type string (as opposed to char), then
you need to pass a buffer into which string pointers (char*) are inserted
so the getVar argument needs to be char** (your second case).
I assume getVar is overloaded so that in the first case it is attempting
to read
a string typed variable using nc_get_vara_text.
In the second case, you are invoking the char** overloaded getVar, so
it is properly invoking nc_get_vara_string function.
=Dennis Heimbigner
Unidata
On 2/27/2019 10:11 PM, Panov Sergey wrote:
I guess it was not a segmentation fault, but a error return triggering
C++ exception. I was able to get it to trigger a real segmentation
fault, but changing
char buffer[20];
inst_var.getVar(buffer);
to
char * buffer;
inst_var.getVar(&buffer);
gives me a pointer to a correct string. It is just bizarre!!! Does it
mean I now can modify that sting and it is OK?
On Thu, 2019-02-28 at 04:31 +0000, Panov Sergey wrote:
I have a very basic question -- how to read "string" variable in C or
C++
The ncdump tells me the variable type is "string". When I try to
read
it using
void getVar(char* dataValues) const;
function of class NcVar of netcdf-cxx4 I am hitting a segmentation
fault. I am not sure why it is a segmentation fault, but it comes
from
...
/* No NC_CHAR conversions, you pervert! */
if (var->type_info->nc_typeid != *mem_nc_type &&
(var->type_info->nc_typeid == NC_CHAR || *mem_nc_type ==
NC_CHAR))
return NC_ECHAR;
...
code in check_for_vara() function in nc4hdf.c .
The var->type_info->nc_typeid is NC_STRING (12) and this check
should
just fail (the reading of the variable should just fail, but it
"throws
an exception" ... causes a segmentation fault for some reason).
The stack is;
check_for_vara nc4hdf.c:477
nc4_get_vara nc4hdf.c:905
nc4_get_vara_tc nc4var.c:1379
NC4_get_vara nc4var.c:1396
NC_get_vara dvarget.c:101
NC_get_var dvarget.c:117
nc_get_var_text dvarget.c:1020
netCDF::NcVar::getVar ncVar.cpp:1340
main cfradial_rd.cpp:47
__libc_start_main 0x00007ffff485a413
_start 0x00000000004021ee
The C++ code is calling C function nc_get_var_text() to read this
string which should have been normal.
What am I doing wrong and what is the right way of reading "string"
variables?
PS. Does anyone else dislike the official C++ library API or it is
just
me?
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