Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: fgets problems
Top Forums Programming fgets problems Post 302397047 by CRGreathouse on Saturday 20th of February 2010 02:29:33 PM
Old 02-20-2010
Quote:
Originally Posted by Corona688
Memory is memory. It doesn't have to track the contents of the pari block to notice clobbering happening outside it.
Sure -- but that's not the problem (and it won't be the problem). Every time the library uses the stack it ensures that there's room for what it's creating. Also, the stack is very large -- at least 20 MB and sometimes as big as 1 GB, with its pointer avma moving by [only] several bytes per call.

The real problem with memory management is leaving garbage on the stack (another possibility is returning corrupted objects). The usual technique for is

Code:
GEN genericfunction(----) {
	pari_sp ltop = avma;	// Keep a pointer to the top of the stack's current location
	GEN r;	// Return value (assigned below)

	// ...
	
	r = gerepileupto(ltop, r);	// copy r to the top of the stack and move avma just above it
	return r;
}

which ensures that you're not leaving garbage on the stack. But this is somewhat more complicated by returning complicated objects like vectors. For example:
Code:
GEN vector = cgetg(4, t_VEC); // Make a vector
gel(vector, 1) = gen_2;
int i = 2;
for(; i < 4; i++)
  gel(vector, i) = addii(gel(vector, i-1), mulii(gel(vector, i-1), gel(vector, i-1))); // v[i] = v[i-1] + v[i-1]^2

Memory diagram:

(vector with pointers to its members A, B, and C)(A)(garbage)(B)(garbage)(C)
 

10 More Discussions You Might Find Interesting

1. UNIX for Advanced & Expert Users

'make' problems (compliation problems?)

I'm trying to compile and install both most recent version of 'make' and the most recent version of 'openssh' on my Sparc20. I've run into the following problems... and I don't know what they mean. Can someone please help me resolve these issues? I'm using the 'make' version that was... (5 Replies)
Discussion started by: xyyz
5 Replies

2. UNIX for Dummies Questions & Answers

Problems with ld.so.1

I renamed ld.so.1 on a Sun machine running Solaris 2.6. Now I cannot boot the system and I can use only very few commands in Maintenance Mode. Can someone help me? (3 Replies)
Discussion started by: ciccio
3 Replies

3. Programming

fgets()

does anyone knows how to accept a command from a user.. i was wondering to use fgets(), but got no idea how to start it... (4 Replies)
Discussion started by: skanky
4 Replies

4. Programming

Problem with fgets and rewind function ..

Hello Friends, I got stuck with fgets () & rewind() function .. Please need help.. Actually I am doing a like, The function should read lines from a txt file until the function is called.. If the data from the txt file ends then it goes to the top and then again when the function is called... (1 Reply)
Discussion started by: user_prady
1 Replies

5. Programming

Question about NULL Character & fgets()

Assume client send the message " Hello ", i get output such as Sent mesg: hello Bytes Sent to Client: 6 bytes_received = recv(clientSockD, data, MAX_DATA, 0); if(bytes_received) { send(clientSockD, data, bytes_received, 0); data = '\0';... (2 Replies)
Discussion started by: f.ben.isaac
2 Replies

6. Programming

[C] fgets problem with SIGINT singlal!!!

Hi all, I have this method to read a string from a STDIN: void readLine(char* inputBuffer){ fgets (inputBuffer, MAX_LINE, stdin); fflush(stdin); /* remove '\n' char from string */ if(strlen(inputBuffer) != 0) inputBuffer = '\0'; } All work fine but if i... (1 Reply)
Discussion started by: hurricane86
1 Replies

7. UNIX for Dummies Questions & Answers

Problems with using less

Hello, I am having problems with using less on Linux version 2.6.18-92.1.17.el5 (brewbuilder@hs20-bc1-7.build.redhat.com) (gcc version 4.1.2 20071124 (Red Hat 4.1.2-42)). I am using csh but have the same problems on bash. If I pipe something to less it works perfectly i.e. cat file | less... (9 Replies)
Discussion started by: z1dane
9 Replies

8. Programming

fgets problems newline

hello, i'm trying to write a C-program that reads a file line by line. (and searches each line for a given string) This file is an special ASCII-database-file, with a lot of entries. I checked the line with most length, and it was about 4000 characters. With google i found several... (4 Replies)
Discussion started by: p1cm1n
4 Replies

9. Programming

fgets read file line with "\n" inside

Hi, I have a string like this, char str ="This, a sample string.\\nThis is the second line, \\n \\n, we will have one blank line"; if I want to use strtok() to seperate the string, which token should I use? I tried "\n", "\\n", either not working. peter (1 Reply)
Discussion started by: laopi
1 Replies

10. Shell Programming and Scripting

while and do problems

Any ideas how to clear this error as it seems I dont understand if,do,while and els commands #!/bin/ksh set -x print "This script creates test messages" print "Please enter test case name" read testcasename echo $testcasename skipfield=Y while print "Do you want to skip this field... (4 Replies)
Discussion started by: andrew.p.mcderm
4 Replies

LEARN ABOUT REDHAT

stack

stack(n)							Tcl Data Structures							  stack(n)

NAME

       stack - Create and manipulate stack objects

SYNOPSIS

       package require Tcl 8.2

       package require struct ?1.2.1?

       stackName option ?arg arg ...?

       stackName clear

       stackName destroy

       stackName peek ?count?

       stackName pop ?count?

       stackName push item ?item ...?

       stackName size

DESCRIPTION

       The  ::struct::stack command creates a new stack object with an associated global Tcl command whose name is stackName.  This command may be
       used to invoke various operations on the stack.	It has the following general form:

       stackName option ?arg arg ...?
	      Option and the args determine the exact behavior of the command.	The following commands are possible for stack objects:

       stackName clear
	      Remove all items from the stack.

       stackName destroy
	      Destroy the stack, including its storage space and associated command.

       stackName peek ?count?
	      Return the top count items of the stack, without removing them from the stack.  If count is not specified, it  defaults  to  1.	If
	      count  is  1,  the  result is a simple string; otherwise, it is a list.  If specified, count must be greater than or equal to 1.	If
	      there are no items on the stack, this command will return count empty strings.

       stackName pop ?count?
	      Return the top count items of the stack, and remove them from the stack.	If count is not specified, it defaults to 1.  If count	is
	      1, the result is a simple string; otherwise, it is a list.  If specified, count must be greater than or equal to 1.  If there are no
	      items on the stack, this command will return count empty strings.

       stackName push item ?item ...?
	      Push the item or items specified onto the stack.	If more than one item is given, they will be pushed in the order they are listed.

       stackName size
	      Return the number of items on the stack.

KEYWORDS

       queue, matrix, tree, graph

struct								       1.2.1								  stack(n)
All times are GMT -4. The time now is 02:36 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy