Memory allocation problem!

J

jois.de.vivre

Hi,

I have the following piece of code that is designed to help me add
debug traces to my program (I wanted to use purely C++ code, but the
only way I know how to do something like this is with macros, so please
don't yell at me):


#include <iostream>
#include <cstdarg>
#include <iomanip>

#define MainDisplay(s, ...) Show( __FILE__, \
__PRETTY_FUNCTION__,\
__LINE__, \
s, \
## __VA_ARGS__);
using namespace std;

void Show(const char* file, const char* fcn, int line, const char*
display, ...)
{
//build display string
va_list va;
va_start(va, display);
char display2[256];
char linestr[10];
vsprintf(display2, display, va);
va_end(va);
sprintf(linestr, "%d", line);

string s = (file + string(" [") + linestr + string("]:"));

//output to console
cout << s;
int ssize = s.size();
if (ssize <= 45) cout << setw(50-ssize) << "" << display2;
else cout << endl << setw(50) << "" << display2;
}


Now I want it to display a very long string message (this string has
548 characters in it):

int main(int argc, char *argv[])
{

MainDisplay("00000001010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101111111111111111111111111111111111111100010000001011000100010000011001111010001100010100111001101001110011010011011011111111111111111111111111111111111111011010100110011100101100000000101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010111111111111111111111111111111111111110001000000101100010001000001100111101000110001010011100110100111001101001101101111111111111111111111111111111111111101101010011001110010110");

return EXIT_SUCCESS;
}



When I run this code I get a segmentation fault, and GDB spews the
following:

Program received signal SIGSEGV, Segmentation fault.
0x00002aaaab06f6a0 in strlen () from /lib64/tls/libc.so.6
(gdb) backtrace
#0 0x00002aaaab06f6a0 in strlen () from /lib64/tls/libc.so.6
#1 0x0000000000401775 in std::char_traits<char>::length
(__s=0x3130313031303130 <Address 0x3130313031303130 out of bounds>) at
char_traits.h:143
#2 0x00000000004015ea in std::eek:perator+<char, std::char_traits<char>,
std::allocator<char> > (__lhs=0x3130313031303130 <Address
0x3130313031303130 out of bounds>, __rhs=@0x7fffffffe9b0) at
basic_string.tcc:692
#3 0x0000000000401232 in Show (file=0x3130313031303130 <Address
0x3130313031303130 out of bounds>, fcn=0x3130313031303130 <Address
0x3130313031303130 out of bounds>, line=825241904,
display=0x3130313031303130 <Address 0x3130313031303130 out of bounds>)
at /home/prashant/Development/test2/src/test2.cpp:20
#4 0x3131303131313131 in ?? ()
#5 0x3131303031303130 in ?? ()
#6 0x3130303131313030 in ?? ()
#7 0x00002a0030313130 in ?? ()
#8 0x0000000000000000 in ?? ()
#9 0x0000000000503028 in ?? ()
#10 0x0000000000400e1b in _init ()
#11 0x00007fffffffed78 in ?? ()
#12 0x0000000100401801 in ?? ()
#13 0
Previous frame inner to this frame (corrupt stack?)
x00002aaaaabc0c60 in ?? () from /lib64/ld-linux-x86-64.so.2
#14 0x00002aaaaabc0c60 in ?? () from /lib64/ld-linux-x86-64.so.2
#15 0x00000000004017e0 in __libc_csu_fini ()
#16 0x00002aaaab00e1d8 in ?? () from /lib64/tls/libc.so.6
#17 0x00007fffffffed78 in ?? ()
#18 0x00000001ffffed88 in ?? ()
#19 0x0000000000401490 in Show () at
/home/prashant/Development/test2/src/test2.cpp:27
(gdb) frame 0
#0 0x00002aaaab06f6a0 in strlen () from /lib64/tls/libc.so.6


If I shorten the string, I find that I get no segmentation fault for
anything less than 313 characters. My assumption is that this is a
'new' or malloc memory limit. ulimit -a returns the following:

core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
file size (blocks, -f) unlimited
max locked memory (kbytes, -l) 32
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
stack size (kbytes, -s) unlimited
cpu time (seconds, -t) unlimited
max user processes (-u) 8191
virtual memory (kbytes, -v) unlimited


I'm running on Suse Linux 9.3 (but I've been able to reproduce this
problem on 9.0) and I'm using gcc 3.4.1.

Any Ideas?

Prashant
 
S

Shezan Baig

#define MainDisplay(s, ...) Show( __FILE__, \
__PRETTY_FUNCTION__,\
__LINE__, \
s, \
## __VA_ARGS__);
using namespace std;

void Show(const char* file, const char* fcn, int line, const char*
display, ...)
{
//build display string
va_list va;
va_start(va, display);
char display2[256];
char linestr[10];
vsprintf(display2, display, va);
Click to expand...




writing to a 256-byte buffer.



va_end(va);
sprintf(linestr, "%d", line);

string s = (file + string(" [") + linestr + string("]:"));

//output to console
cout << s;
int ssize = s.size();
if (ssize <= 45) cout << setw(50-ssize) << "" << display2;
else cout << endl << setw(50) << "" << display2;
}


Now I want it to display a very long string message (this string has
548 characters in it):

int main(int argc, char *argv[])
{

MainDisplay("00000001010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101111111111111111111111111111111111111100010000001011000100010000011001111010001100010100111001101001110011010011011011111111111111111111111111111111111111011010100110011100101100000000101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010111111111111111111111111111111111111110001000000101100010001000001100111101000110001010011100110100111001101001101101111111111111111111111111111111111111101101010011001110010110");
Click to expand...




sending 548 bytes into a 256 byte buffer



return EXIT_SUCCESS;
}



When I run this code I get a segmentation fault, and GDB spews the
following:
[snip]


Any Ideas?
Click to expand...


you are overflowing your buffer.

-shez-
 
D

David Resnick

[email protected] said:
Hi,

I have the following piece of code that is designed to help me add
debug traces to my program (I wanted to use purely C++ code, but the
only way I know how to do something like this is with macros, so please
don't yell at me):
Click to expand...

For the future, you should either post in comp.lang.c++ for
C++ programs, or if for some reason you need C language input,
reduce your problem to a compilable C program and post there.
#include <iostream>
#include <cstdarg>
#include <iomanip>

#define MainDisplay(s, ...) Show( __FILE__, \
__PRETTY_FUNCTION__,\
__LINE__, \
s, \
## __VA_ARGS__);
using namespace std;

void Show(const char* file, const char* fcn, int line, const char*
display, ...)
{
//build display string
va_list va;
va_start(va, display);
char display2[256];
char linestr[10];
vsprintf(display2, display, va);
Click to expand...

Why do you think that this will work if you are putting in
more that 256 bytes into display2? It will overrun memory.
You either need to make display2 bigger than any possible input
(how can you do that?) or use vsnprintf and truncate, probably a
better bet.

-David
 
C

Chris Hulbert

Hi,

I have the following piece of code that is designed to help me add
debug traces to my program (I wanted to use purely C++ code, but the
only way I know how to do something like this is with macros, so please
don't yell at me):
Click to expand...

Perhaps you didn't notice this is comp.lang.c, not comp.lang.c++.
Anyways, look at your vspintf: vsprintf(display2, display, va);

display2 is char[256]. display is 548 (as you said in the main, i did
not count them). See anything wrong with that? You're overrunning the
buffer!
try vsnprintf.

#include <iostream>
#include <cstdarg>
#include <iomanip>

#define MainDisplay(s, ...) Show( __FILE__, \
__PRETTY_FUNCTION__,\
__LINE__, \
s, \
## __VA_ARGS__);
using namespace std;

void Show(const char* file, const char* fcn, int line, const char*
display, ...)
{
//build display string
va_list va;
va_start(va, display);
char display2[256];
char linestr[10];
vsprintf(display2, display, va);
va_end(va);
sprintf(linestr, "%d", line);

string s = (file + string(" [") + linestr + string("]:"));

//output to console
cout << s;
int ssize = s.size();
if (ssize <= 45) cout << setw(50-ssize) << "" << display2;
else cout << endl << setw(50) << "" << display2;
}


Now I want it to display a very long string message (this string has
548 characters in it):

int main(int argc, char *argv[])
{

MainDisplay("00000001010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101111111111111111111111111111111111111100010000001011000100010000011001111010001100010100111001101001110011010011011011111111111111111111111111111111111111011010100110011100101100000000101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010111111111111111111111111111111111111110001000000101100010001000001100111101000110001010011100110100111001101001101101111111111111111111111111111111111111101101010011001110010110");

return EXIT_SUCCESS;
}



When I run this code I get a segmentation fault, and GDB spews the
following:

Program received signal SIGSEGV, Segmentation fault.
0x00002aaaab06f6a0 in strlen () from /lib64/tls/libc.so.6
(gdb) backtrace
#0 0x00002aaaab06f6a0 in strlen () from /lib64/tls/libc.so.6
#1 0x0000000000401775 in std::char_traits<char>::length
(__s=0x3130313031303130 <Address 0x3130313031303130 out of bounds>) at
char_traits.h:143
#2 0x00000000004015ea in std::eek:perator+<char, std::char_traits<char>,
std::allocator<char> > (__lhs=0x3130313031303130 <Address
0x3130313031303130 out of bounds>, __rhs=@0x7fffffffe9b0) at
basic_string.tcc:692
#3 0x0000000000401232 in Show (file=0x3130313031303130 <Address
0x3130313031303130 out of bounds>, fcn=0x3130313031303130 <Address
0x3130313031303130 out of bounds>, line=825241904,
display=0x3130313031303130 <Address 0x3130313031303130 out of bounds>)
at /home/prashant/Development/test2/src/test2.cpp:20
#4 0x3131303131313131 in ?? ()
#5 0x3131303031303130 in ?? ()
#6 0x3130303131313030 in ?? ()
#7 0x00002a0030313130 in ?? ()
#8 0x0000000000000000 in ?? ()
#9 0x0000000000503028 in ?? ()
#10 0x0000000000400e1b in _init ()
#11 0x00007fffffffed78 in ?? ()
#12 0x0000000100401801 in ?? ()
#13 0
Previous frame inner to this frame (corrupt stack?)
x00002aaaaabc0c60 in ?? () from /lib64/ld-linux-x86-64.so.2
#14 0x00002aaaaabc0c60 in ?? () from /lib64/ld-linux-x86-64.so.2
#15 0x00000000004017e0 in __libc_csu_fini ()
#16 0x00002aaaab00e1d8 in ?? () from /lib64/tls/libc.so.6
#17 0x00007fffffffed78 in ?? ()
#18 0x00000001ffffed88 in ?? ()
#19 0x0000000000401490 in Show () at
/home/prashant/Development/test2/src/test2.cpp:27
(gdb) frame 0
#0 0x00002aaaab06f6a0 in strlen () from /lib64/tls/libc.so.6


If I shorten the string, I find that I get no segmentation fault for
anything less than 313 characters. My assumption is that this is a
'new' or malloc memory limit. ulimit -a returns the following:

core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
file size (blocks, -f) unlimited
max locked memory (kbytes, -l) 32
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
stack size (kbytes, -s) unlimited
cpu time (seconds, -t) unlimited
max user processes (-u) 8191
virtual memory (kbytes, -v) unlimited


I'm running on Suse Linux 9.3 (but I've been able to reproduce this
problem on 9.0) and I'm using gcc 3.4.1.

Any Ideas?

Prashant
Click to expand...
 
M

Martin Ambuhl

Hi,

I have the following piece of code that is designed to help me add
debug traces to my program (I wanted to use purely C++ code,
Click to expand...

This makes no sense. No rational person posts to comp.lang.c if he has
a C++-related question.
but the
only way I know how to do something like this is with macros, so please
don't yell at me):


#include <iostream>
#include <cstdarg>
#include <iomanip>
Click to expand...

This stuff, which is not C, is reason enough for comp.lang.c people to
yell at you.
#define MainDisplay(s, ...) Show( __FILE__, \
__PRETTY_FUNCTION__,\
Click to expand...

And this, which is implementation-specific, should get the comp.lang.c++
people on you.

It seems that you are writing g++-specific code. You need to post such
questions to a gnu.* newsgroup.
 
J

jois.de.vivre

If you don't have anything useful to say in reference to my original
question (which you don't), don't bother replying. I already said
that this is the only way I know how to do something like this and it's
enough for you to read it and move on if you can't figure out the
solution. Obviously the problem was simple enough that people in
comp.lang.c could help me solve it, so why do you bother wasting your
time writing such condescending responses.
 
A

Alf P. Steinbach

* (e-mail address removed) -> Martin Ambuhl:
If you don't have anything useful to say in reference to my original
question (which you don't), don't bother replying. I already said
that this is the only way I know how to do something like this and it's
enough for you to read it and move on if you can't figure out the
solution. Obviously the problem was simple enough that people in
comp.lang.c could help me solve it, so why do you bother wasting your
time writing such condescending responses.
Click to expand...

Idiot.

Cheers,

- Alf
 
C

CBFalconer

If you don't have anything useful to say in reference to my original
question (which you don't), don't bother replying. I already said
that this is the only way I know how to do something like this and
it's enough for you to read it and move on if you can't figure out
the solution. Obviously the problem was simple enough that people
in comp.lang.c could help me solve it, so why do you bother wasting
your time writing such condescending responses.
Click to expand...

They and you are both wrong, in that C++ answers should not be
given in c.l.c, because they will not be properly examined and they
will encourage further off-topic postings. You do not seem to have
managed to figure out how to use google groups, and I am tired of
instructing idiots how to so do. You will go far, but probably at
the end of a boot.
 
R

Richard Herring

If you don't have anything useful to say in reference to my original
question (which you don't), don't bother replying.
Click to expand...

If you must post via Google, please learn how to make it quote some
context.
 
J

jois.de.vivre

They and you are both wrong, in that C++ answers should not be
given in c.l.c, because they will not be properly examined and they
will encourage further off-topic postings. You do not seem to have
managed to figure out how to use google groups, and I am tired of
instructing idiots how to so do. You will go far, but probably at
the end of a boot.
Click to expand...

It seems to me my question was properly examined, and was properly
answered. Nobody is asking you to instruct anybody on how to use
google groups, so if you're tired of instructing idiots, then stop
instructing. Simple. It takes all but two seconds to read a post and
realize that it's "off topic". In fact I explicitly stated in my
opening that I was using C++ but that I needed help with part of my C
code, which should have given you a clue. So stop crying.
 

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