Solved

Gnu C - segmentation fault

Posted on 1998-05-05
3
354 Views
Last Modified: 2012-05-04
Hello, I have problems with the following script, in which I tried to "copy" the C library function strtod with the GNU inline assembler:

#include "stdio.h"
#include "stdlib.h"

double TGIstrtod(const char *nptr, char **endptr) {

     long a;
     double returnvalue;
     long b;
     double c;
     long d;
     d = (long)*endptr;
     __asm__ __volatile__(
//here comes the assembler part...
//...
       :"=m" (returnvalue)
       :"S" (nptr), "m" (errno), "m" (a), "m" (b), "m" (c), "m" (d)
       :"eax","ebx","edx");
     *endptr = (char*)d;
     return returnvalue;
}


void main (int argc, char *argv[]){
  char **s;
  *s = ".";
  if (argc > 1) {
     printf("Float: %.10e\n",  TGIstrtod (argv[1],(char **)s));
     printf("%s\n",*s); }
   else printf ("Please run with parameter!!");
}

I get the segmentations fault in the lines *s = "." and if I submit a parameter. I think there's a problem with s, but - being very unfamiliar with C - I don't know why. Any help if greatly appreciated!
0
Comment
Question by:Christian_Wenz
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
3 Comments
 
LVL 51

Accepted Solution

by:
ahoffmann earned 100 total points
ID: 1635066
*s is a pointer, you need to alloc memory befor you assign values
0
 
LVL 5

Author Comment

by:Christian_Wenz
ID: 1635067
this might be it. I also found out that I should replace char **)s by &s and put char *s instead of char **s. But how do I allocate memory?
0
 
LVL 51

Expert Comment

by:ahoffmann
ID: 1635068
...
char *s = NULL;
s = malloc(100); /* replace 100 by an appropriate value */
if (s == NULL) {
  printf("error: malloc failed.\n"); exit(1);
}
...
    TGIstrtod(argv[1], &s)
...

Keep in mind that you allocate enough memory for s (used in
TGIstrtod, 'cause it does not check the size of the given
pointer).
0

Featured Post

Microsoft Certification Exam 74-409

Veeam® is happy to provide the Microsoft community with a study guide prepared by MVP and MCT, Orin Thomas. This guide will take you through each of the exam objectives, helping you to prepare for and pass the examination.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Setting up Secure Ubuntu server on VMware 1.      Insert the Ubuntu Server distribution CD or attach the ISO of the CD which is in the “Datastore”. Note that it is important to install the x64 edition on servers, not the X86 editions. 2.      Power on th…
Google Drive is extremely cheap offsite storage, and it's even possible to get extra storage for free for two years.  You can use the free account 15GB, and if you have an Android device..when you install Google Drive for the first time it will give…
Learn several ways to interact with files and get file information from the bash shell. ls lists the contents of a directory: Using the -a flag displays hidden files: Using the -l flag formats the output in a long list: The file command gives us mor…
This demo shows you how to set up the containerized NetScaler CPX with NetScaler Management and Analytics System in a non-routable Mesos/Marathon environment for use with Micro-Services applications.
Suggested Courses

738 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question