This feature is disabled by the command sysctl -w kernel.core_uses_pid = 0. in Java Implement PDF417 in Java This feature is disabled by the command sysctl -w kernel.core_uses_pid = 0.

7. This feature is disabled by the command sysctl -w kernel.core_uses_pid = 0. using barcode maker for servlet control to generate, create barcode pdf417 image in servlet applications. GS1 DataBar Getting Comfortable with the GNU Debugger: gdb Knowing that your program corrupted the stack is useful information, but unfortunately, gdb doesn t come right out and tell you this. The only clue you get to this event is when the functions listed in the backtrace command make no sense for the program you are running, or gdb might just tell you no stack. The most common cause of stack corruption is a buffer overflow of a local variable.

You might declare an array on the stack and use memset or memcpy to initialize the array to too large a size. In general, any time you take a pointer to a local variable and give it to another function, you create the risk of an overrun. This opportunity for buffer overflow is possible with scanf, read, and many other functions.

The program in Listing 10-6 is an implementation of the factorial function I described earlier in the chapter. This is commonly used in statistical applications and in computer-science classes as an example of recursive programming.8.

LISTING 10-6. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23. factorial.c: An Example of Stack Corruption #include <stdio .h> #include <string.h> #include <stdlib.

h> // factorial function. Traditional programming example // of a recursive function. int factorial(int x) { int overflow; static int depth = 0; if (x <= 1) return 1; if (++depth > 6) { // Overflow n bytes.

Will cause a SIGSEGV, but we don"t know where. int n = 0x100; memset((char *) &overflow, 0xa5, sizeof(overflow) + n); } return x * factorial(x - 1); }. continues 8. Infinite recurs ion is a common programming bug that leads to a SIGSEGV but not necessarily to stack corruption..

10 Debugging 24 int main(int ar gc, char *argv[]) 25 { 26 int n = 3; 27 printf("Command line argument > 7 will cause stack corruption\n"); 28 if (argc > 1) { 29 n = atoi(argv[1]); 30 } 31 printf("%d! == %d\n", n, factorial(n)); 32 return 0; 33 }. In this contrived tomcat PDF-417 2d barcode example, you deliberately trash the stack after the function has called itself seven times. To do this, you write 256 bytes to the address of an integer local variable. Here it is in action:.

$ ./factorial 7 Co mmand line argument > 7 will cause stack corruption 7! == 5040 $ ./factorial 8 Command line argument > 7 will cause stack corruption Segmentation fault (core dumped) Told you so! $ gdb .

/factorial core GNU gdb Red Hat Linux (6.3.0.

0-1.21rh) ..

. Core was generated by `./factorial 8".

Program terminated with signal 11, Segmentation fault. ..

. #0 0xa5a5a5a5 in () This is not looking good. (gdb) bt Let s look at the backtrace.

#0 0xa5a5a5a5 in () #1 0xa5a5a5a5 in () #2 0xa5a5a5a5 in () #3 0xa5a5a5a5 in () ...

OK, that wasn t helpful. #21 0xa5a5a5a5 in () #22 0xa5a5a5a5 in () ---Type <return> to continue, or q <return> to quit---q Quit (gdb)p factorial::depth Static variables are still OK. $1 = 7.

After the program j2se PDF-417 2d barcode dumps core, you use gdb to attempt postmortem debugging and find that the stack is unusable. Your clue is that the backtrace command (bt) shows nothing useful. You can still use this core file, however.

You only need stack frames to look at local variables. All static and global variables are still visible. To look at the static variable depth defined inside the function factorial, use C++ syntax: factorial::depth.

Examining this value tells you that you called factorial seven times recursively. In this case, that s almost as good as a stack trace..

Getting Comfortable with the GNU Debugger: gdb Unfortunately, mos barcode pdf417 for Java t programs aren t this easy to debug. If you are debugging a program that is exhibiting stack corruption, you can consider adding global or static variables for the purpose of postmortem debugging. I explore this idea further in the section Creating Your Own Black Box later in this chapter.

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