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problem with memory allocation

From: Kjetil Haaland <kjetil(dot)haaland(at)student(dot)uib(dot)no>
To: pgsql-novice(at)postgresql(dot)org
Subject: problem with memory allocation
Date: 2004-11-26 14:56:41
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-novice
Hello all
Sorry for asking so many question about this topic, but i don't get it to 
work. The problem is when i allocate memory for char pointers (char*). I have 
a function that i run many times in my db. The first time i allocate memory 
for the char* it is ok, and it is set to the length that i say it should 
have. In the next round, i give a smaller input and tries to allocate memory 
for this. 

The first problem is when i try to print out the pointer after the allocation, 
but before the insert it is what i inserted the last time i used the 
The second problem, coming from the first, is that it has the length from the 
first allocation, not the length that i set it to have.
Here is some of the code i use:
alignres *align = (alignres *) PG_GETARG_POINTER(0);
char *first = NULL;
char *second = NULL;
int secondStart=align->secondString;
char tempBuffer[strlen(align->stringBuffer)+1];

elog(NOTICE, "before allocating:first=%s, second=%s", first, second);	
first = (char*) palloc(sizeof(char)*secondStart);
second = (char*) palloc(sizeof(char)*(strlen(align->stringBuffer)
elog(NOTICE, "after allocating:first=%s, second=%s", first, second);
elog(NOTICE, "length: first=%d, second=%d", strlen(first), strlen(second));

snprintf(tempBuffer, sizeof(tempBuffer), "%s", align->stringBuffer);
snprintf(first, secondStart, "%s", tempBuffer);
first[strlen(first)] = '\0';

int j=0;
for(i=secondStart-1; i < (strlen(align->stringBuffer)); i++) {
	second[j] = tempBuffer[i];
second[strlen(second)] = '\0';


I am i doing the allocation correct?
Is there any other way to free the memory so first and second is not set to 
the value that the memory was last used for?



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