I put together a C function to add strings to a dynamic array of strings (mostly for educational purpose to explain pointers to my kid). It works, but sometimes one or two strings in the array becomes corrupted. Running example on 64 bit Ubuntu, gcc ver. 4.8.4
Hope my code is self-explanatory:
And here is the culprit, I removed error checking and temp pointer to hold results of the realloc for brevity:
Result:
The length of those strings does not seem to matter. If I have 2 - 3 strings in the array it is OK, but when I add more than 4 then some strings got corrupted.
When I debug I see it happens when indx is 4 and I assign address of duplicated string to the array: arr[0][indx] = strdup(str);
Any help with finding the bug would be appreciated.
Also, I hate the [0][indx] notation, but could not come up with a better one.
I am facing a strange error while creating posix threads:
Given below are two snippets of code, the first one works whereas the second one gives a garbage value in the output.
Snippet 1
This works:
--------------
int *threadids;
threadids = (int *) malloc (num_threads * sizeof(int));
... (4 Replies)
Hello, everyone.
I got the following error when I am using awk to analysis some text file:
*** glibc detected *** awk: malloc(): memory corruption: 0x080c67f8 ***
======= Backtrace: =========
/lib/tls/i686/cmov/libc.so.6
/lib/tls/i686/cmov/libc.so.6... (5 Replies)
there seems not to be error in this segment. In some computers, it can work well. But in others, it will give a failure.
why it ocurrs and how to deal with it?
in a function:
if( *ver == NULL ) {
*ver = (vertex *) malloc(sizeof(vertex)); //this line
... (17 Replies)
Hi every body
I have a problem like that "Dynamic linker error" message.
I can't load many of programs in sco unix openserver 5.0.6.
I guess this problem appear after my last effort to install "SCO Development System" package.
How can I fix this problem?
would you please help me ? (1 Reply)
Hi everyone
I am developing an utility.
At some part of it I read directory entries to a dynamic array: struct list
It stores pointers to items: list.entries,
which are structures: struct entry
If a number of files in a directory is greater then number of elements an array was initially... (11 Replies)
Hi All,
I have a simple code which does some computation by matching string patterns.
In brief:
1. The code reads .dat and .txt files.
2. .dat files are huge text files and .txt files contain some important words.
3. I am just doing strstr to find the patterns.
4. The function returns the... (3 Replies)
*** glibc detected *** ./a.out: malloc(): memory corruption (fast):
Posted A minute ago
M trying to make multiway tree and dont know what happend when this part of code get executed:
01void ins(NODE *ptr)
02{
03 //working
04 if(ptr!=NULL)
05 {
06 SNODE *var=NULL;
07 var=(SNODE... (3 Replies)
I am facing a problem of memory corruption. The loop runs for the first time but does not go through the second time. What could be the problem?
for(int z=0;z<2;z++)
{
fp=fopen("poly.dat","r");
/*do something which reads this file into a 2D array*/
fclose(fp);
... (10 Replies)
I am having a problem with shared memory corruption. I have two 86 servers running Solaris 10 (150400-06). One of the servers is accessed by a Sun Ray thin client Version 11.1.3.0.2.6. I login into server one from the thin client. I then ssh -X to server two. When a process that contains a... (2 Replies)
Discussion started by: salerno
2 Replies
LEARN ABOUT SUSE
librrd
librrd(3) rrdtool librrd(3)NAME
librrd - RRD library functions
DESCRIPTION
librrd contains most of the functionality in RRDTool. The command line utilities and language bindings are often just wrappers around the
code contained in librrd.
This manual page documents the librrd API.
NOTE: This document is a work in progress, and should be considered incomplete as long as this warning persists. For more information
about the librrd functions, always consult the source code.
CORE FUNCTIONS
rrd_dump_cb_r(char *filename, int opt_header, rrd_output_callback_t cb, void *user)
In some situations it is necessary to get the output of "rrd_dump" without writing it to a file or the standard output. In such cases
an application can ask rrd_dump_cb_r to call an user-defined function each time there is output to be stored somewhere. This can be
used, to e.g. directly feed an XML parser with the dumped output or transfer the resulting string in memory.
The arguments for rrd_dump_cb_r are the same as for rrd_dump_opt_r except that the output filename parameter is replaced by the user-
defined callback function and an additional parameter for the callback function that is passed untouched, i.e. to store information
about the callback state needed for the user-defined callback to function properly.
Recent versions of rrd_dump_opt_r internally use this callback mechanism to write their output to the file provided by the user.
size_t rrd_dump_opt_cb_fileout(
const void *data,
size_t len,
void *user)
{
return fwrite(data, 1, len, (FILE *)user);
}
The associated call for rrd_dump_cb_r looks like
res = rrd_dump_cb_r(filename, opt_header,
rrd_dump_opt_cb_fileout, (void *)out_file);
where the last parameter specifies the file handle rrd_dump_opt_cb_fileout should write to. There's no specific condition for the
callback to detect when it is called for the first time, nor for the last time. If you require this for initialization and cleanup you
should do those tasks before and after calling rrd_dump_cr_r respectively.
UTILITY FUNCTIONS
rrd_random()
Generates random numbers just like random(). This further ensures that the random number generator is seeded exactly once per process.
rrd_add_ptr(void ***dest, size_t *dest_size, void *src)
Dynamically resize the array pointed to by "dest". "dest_size" is a pointer to the current size of "dest". Upon successful realloc(),
the "dest_size" is incremented by 1 and the "src" pointer is stored at the end of the new "dest". Returns 1 on success, 0 on failure.
type **arr = NULL;
type *elem = "whatever";
size_t arr_size = 0;
if (!rrd_add_ptr(&arr, &arr_size, elem))
handle_failure();
rrd_add_strdup(char ***dest, size_t *dest_size, char *src)
Like "rrd_add_ptr", except adds a "strdup" of the source string.
char **arr = NULL;
size_t arr_size = NULL;
char *str = "example text";
if (!rrd_add_strdup(&arr, &arr_size, str))
handle_failure();
rrd_free_ptrs(void ***src, size_t *cnt)
Free an array of pointers allocated by "rrd_add_ptr" or "rrd_add_strdup". Also frees the array pointer itself. On return, the source
pointer will be NULL and the count will be zero.
/* created as above */
rrd_free_ptrs(&arr, &arr_size);
/* here, arr == NULL && arr_size == 0 */
rrd_mkdir_p(const char *pathname, mode_t mode)
Create the directory named "pathname" including all of its parent directories (similar to "mkdir -p" on the command line - see mkdir(1)
for more information). The argument "mode" specifies the permissions to use. It is modified by the process's "umask". See mkdir(2) for
more details.
The function returns 0 on success, a negative value else. In case of an error, "errno" is set accordingly. Aside from the errors
documented in mkdir(2), the function may fail with the following errors:
EINVAL
"pathname" is "NULL" or the empty string.
ENOMEM
Insufficient memory was available.
any error returned by stat(2)
In contrast to mkdir(2), the function does not fail if "pathname" already exists and is a directory.
AUTHOR
RRD Contributors <rrd-developers@lists.oetiker.ch>
1.4.3 2009-11-15 librrd(3)