Databases
StackOverflow2013
Postsdbo
POMemory allocation error - in Linux but not OSX Unix
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POMemory allocation error - in Linux but not OSX Unix
    primarykey
    data
    text
    <p>I'm writing some code for a statistics package, and I start off by reading in data to a pointer array. I initialize the pointer and allocate sufficient memory using malloc; however, I sometimes get an error in the memory allocation at the end of the code below. </p> <pre><code>#include &lt;stddef.h&gt; #include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include "stats.h" int main(int argc, char **argv) { FILE *fp, *outFile, *outBin; // create a file identifier size_t n, nbins; // # of data points double *data; // pointer to hold data double average, variance, *med; // stat returns int medianComplete, histComplete, i; // return 1 on success hist_t *Histogram; // read in the number of bins from exe arguments nbins = atoi(argv[1]); nbins = (size_t)nbins; // open the binary datafile and read in first value // which is number of data points // use exe input for filename fp = fopen(argv[2],"rb"); fread(&amp;n, sizeof(size_t),1,fp); // allocate enough memory to hold all data data = (double*)malloc(sizeof(double)*n); if (!data) printf("Memory allocation error"); fread(data,sizeof(double),n,fp); </code></pre> <p>This program compiles and runs well on my personal machine (MacOSX), but fails due to a segmentation error when I try to run it on a Linux server. I used Valgrind to see if I could track down the error and I receive the following result.</p> <pre><code>==8641== Warning: silly arg (-501426814648844128) to malloc() ==8641== Invalid write of size 1 ==8641== at 0x4C2B20D: mempcpy (mc_replace_strmem.c:956) ==8641== by 0x4EA2F15: _IO_file_xsgetn (fileops.c:1423) ==8641== by 0x4E971D2: fread (iofread.c:44) ==8641== by 0x40086D: main (runstats.c:28) ==8641== Address 0x0 is not stack'd, malloc'd or (recently) free'd </code></pre> <p>This is the first program I've ever written that uses pointers, and I'm at a loss for why it would work on one system but not the other.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USolibre
    1. USdwv5009
    plurals
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COAdded in a test of the file pointer, and fopen() is successful. Valgrind indicates that the error occurs when I allocate memory to data. The check I perform on data fails on the server, but passes on my own computer.
      singulars
      1. POMemory allocation error - in Linux but not OSX Unix
      1. USdwv5009
    2. COFirst thouht that comes when I see the question is: "Why is he doing this in C, when there are dozens of more suitable languages?.."
      singulars
      1. POMemory allocation error - in Linux but not OSX Unix
      1. USvines
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload