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 FREEBSD
dwarf_loclist_n
DWARF_LOCLIST(3) BSD Library Functions Manual DWARF_LOCLIST(3)NAME
dwarf_loclist, dwarf_loclist_n -- retrieve DWARF location expression information
LIBRARY
DWARF Access Library (libdwarf, -ldwarf)
SYNOPSIS
#include <libdwarf.h>
int
dwarf_loclist(Dwarf_Attribute at, Dwarf_Locdesc **llbuf, Dwarf_Signed *listlen, Dwarf_Error *error);
int
dwarf_loclist_n(Dwarf_Attribute at, Dwarf_Locdesc ***llbuf, Dwarf_Signed *listlen, Dwarf_Error *error);
DESCRIPTION
These functions retrieve the location expressions associated with a DWARF attribute.
Note: function dwarf_loclist() is deprecated. New application code should instead use function dwarf_loclist_n()
Function dwarf_loclist_n() retrieves the list of location expressions associated with a DWARF attribute. Argument at should reference a
valid DWARF attribute. Argument llbuf should point to a location which will hold a returned array of pointers to Dwarf_Locdesc descriptors.
Argument listlen should point to a location which will be set to the number of elements contained in the returned array. If argument err is
not NULL, it will be used to store error information in case of an error.
Function dwarf_loclist() retrieves the first location expression associated with an attribute. Argument at should reference a valid DWARF
attribute. Argument llbuf should point to a location which will hold the returned pointer to a Dwarf_Locdesc descriptor. Argument listlen
should point to a location which will be always set to 1. If argument err is not NULL, it will be used to store error information in case of
an error.
Dwarf_Locdesc descriptors are defined in the header file <libdwarf.h>, and consist of following fields:
ld_lopc The lowest program counter address covered by the descriptor. This field will be set to 0 if the descriptor is not associated with
an address range.
ld_hipc The highest program counter address covered by the descriptor. This field will be set to 0 if the descriptor is not associated
with an address range.
ld_cents The number of entries returned in ld_s field.
ld_s Pointer to an array of Dwarf_Loc descriptors.
Each Dwarf_Loc descriptor represents one operation of a location expression. These descriptors are defined in the header file <libdwarf.h>,
and consist of following fields:
lr_atom The operator name, one of the DW_OP_* constants defined in the header file <dwarf.h>.
lr_number The first operand of this operation.
lr_number2 The second operand of this operation.
lr_offset The byte offset of this operation within the containing location expression.
Memory Management
The memory area used for the descriptor array returned in argument llbuf is allocated by the DWARF Access Library (libdwarf, -ldwarf). When
the descriptor array is no longer needed, application code should use function dwarf_dealloc(3) to free the memory area in the following man-
ner:
1. First, the ld_s field of each Dwarf_Locdesc descriptor should be deallocated using the allocation type DW_DLA_LOC_BLOCK.
2. Then, the application should free each Dwarf_Locdesc descriptor using the allocation type DW_DLA_LOCDESC.
3. Finally, the llbuf pointer should be deallocated using the allocation type DW_DLA_LIST.
RETURN VALUES
On success, these functions returns DW_DLV_OK. In case of an error, they return DW_DLV_ERROR and set the argument err.
ERRORS
These functions can fail with:
[DW_DLE_ARGUMENT] One of the arguments at, llbuf or listlen was NULL.
[DW_DLE_ARGUMENT] The attribute provided by argument at does not contain a location expression or is not associated with a location expres-
sion list.
EXAMPLE
To retrieve the location list associated with an attribute, use:
Dwarf_Attribute at;
Dwarf_Locdesc **llbuf;
Dwarf_Signed lcnt;
Dwarf_Loc *lr;
Dwarf_Error de;
int i;
if (dwarf_loclist_n(at, &llbuf, &lcnt, &de) != DW_DLV_OK)
errx(EXIT_FAILURE, "dwarf_loclist_n failed: %s",
dwarf_errmsg(de));
for (i = 0; i < lcnt; i++) {
/* ... Use llbuf[i] ... */
for (j = 0; (Dwarf_Half) j < llbuf[i]->ld_cents; j++) {
lr = &llbuf[i]->ld_s[j];
/* ... Use each Dwarf_Loc descriptor ... */
}
dwarf_dealloc(dbg, llbuf[i]->ld_s, DW_DLA_LOC_BLOCK);
dwarf_dealloc(dbg, llbuf[i], DW_DLA_LOCDESC);
}
dwarf_dealloc(dbg, llbuf, DW_DLA_LIST);
SEE ALSO dwarf(3), dwarf_dealloc(3), dwarf_loclist_from_expr(3), dwarf_loclist_from_expr_a(3), dwarf_get_loclist_entry(3)BSD November 9, 2011 BSD