asked on

copying strings to a structure field

Hi Experts,

I have the following in the .h file

typedef struct
{
char *name;
char *value;
} my_table_t;

void functionOne(my_table_t *table);

And I am doing something like below to copy some data. I want to know if this valid or should I use strcpy to copy the values.

my_table_t table;

table.name = "nameOne";
table.value = "valueOne";

functionOne(&table);

ozo

It can be valid, depending on what you want to do with functionOne
In particular, what might happen if you tried to write to *(table.name) or *(table.value) would be undefined.

ambuli

ASKER

functionOne is basically used for getting the xml message representing this C structure. So, I am using libXML2 to get the xml messages.

So, it is used something like below.

string_field = xmlNewChild(new_tuple, NULL, "StringField", NULL);
xmlNewChild(string_field, NULL, "Name", "nameOne");
xmlNewChild(string_field, NULL, "Value", table->name);

What I am trying to debug is that I am getting the following error, possibly from libXml2. So, I am trying to see if my copying is incorrect.

xmlEscapeEntities : char out of range

SOLUTION

ozo

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ambuli

ASKER

It appears that
when I do this,

table->name contains some trailing bytes( garbage characters...)
A bit more details.

I am getting the value from SPI_getvalue( ) from postgres database, which returns char *.

So,

table->name = SPI_getvalue();

functionOne(&table);

...
In functionOne( )

xmlNewChild(string_field, NULL, "Value", table->name);

evilrix

It would probably be best of you just posted the code here. Unfortunately, what the code codes and what you describe may be orthogonal. With code to view we can try to diagnose the issue rather than conjecture based upon the symptoms you describe.

-Rx.

evilrix

s/what the code codes/what the code does

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evilrix

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SOLUTION

jkr

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evilrix

>> You need to allocate memory for these variables, just assigning pointer values does not guarantee the validity of the data
"The result is returned in memory allocated using palloc. (You can use pfree to release the memory when you don't need it anymore.) "
http://www.postgresql.org/docs/8.2/static/spi-spi-getvalue.html

ambuli

ASKER

Sorry, I was tied up with something else and couldn't comment on this. The code is pretty much identical to what I described. It is a larger program, and I wasn't able to simplify that to post here. Anyway, thanks for all your inputs.