I see a lot of solutions to resolving the problem exemplified by      Illegal instruction (core dumped)   But, I'm wondering what exactly that means? What generates that error, and what's the root cause of it? Is that the CPU getting someone it believes is an instruction but can't decode? What happens under the hood to generate that error?  From dmesg, I see  [429572.598803] traps: test[4054] trap invalid opcode ip:400066 sp:ffac8cc0 error:0 in test[400000+1000] [429758.598292] traps: test[4401] trap invalid opcode ip:400066 sp:ffa3f990 error:0 in test[400000+1000] [430066.170626] traps: test[4854] trap invalid opcode ip:400066 sp:ff8ab000 error:0 in test[400000+1000] [430439.855002] traps: test[5212] trap invalid opcode ip:8048071 sp:ffce2fa0 error:0 in test[8048000+1000]
101553
I sometimes get a little confused by all of the signals that a process can receive. As I understand it, a process has a default handler (signal disposition) for each of these signals, but it can provide its own handler by calling .  So here is my question: what causes each of the signals to be sent? I realize that you can manually send signals to running processes via the -s parameter to kill, but what are the natural circumstances under which these signals are sent? For example, when does SIGINT get sent?  Also, are there any restrictions on which signals can be handled? Can even SIGSEGV signals be processed and control returned to the application?
84590
I have a notebook here that I suspect has a faulty memory module. I therefore downloaded  and let it run.  Note that the screenshot is not my actual one, it's provided by memtest86+    How do I interpret the numbers on the screen? I've let it run for about four hours and now I'm in pass 7.  Especially, what does   the test number the count of Errors the count of ECC errors   indicate? What are sane values for memory errors? At which point should I consider replacing memory?
94738
Whilst analysing some legacy code with FXCop, it occurred to me is it really that bad to catch a general exception error within a try block or should you be looking for a specific exception.  Thoughts on a postcard please.
52027
I'm confused. Running Fedora Linux, lscpu yields:  Architecture:            i686 CPU op-mode(s):          32-bit, 64-bit ...   But when I try to install a 64-bit program (Chrome) I get error like:     Package /....x86_64.rpm has incompatible architecture x86_64. Valid architectures are ['i686', 'i586', 'i486', i386']   I'm less interested in being able to install Chrome and more interested in why lscpu says that my CPU can run in 64-bit mode; clearly this can't mean I can run 64-bit programs. Can anyone clarify?
5063
I have a production server running with the following flag: -XX:+HeapDumpOnOutOfMemoryError  Last night it generated a java-38942.hprof file when our server encountered a heap error. It turns out that the developers of the system knew of the flag but no way to get any useful information from it.  Any ideas?
55096
Ok, I've always, for some reason, thought that my cpu had 32 bit registers... so I always installed the 32bit version of all OSs that I've used. Now though I ran a lscpu, and I get:  fer@fer-lap:~$ lscpu Arquitectura:          i686 CPU op-mode(s):        32-bit, 64-bit   Does this mean I can use 64 bit OSs?  Running these I get:  fer@fer-lap:~$ grep flags /proc/cpuinfo  flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm   And I have read that the lm flag means long mode, which stands for 64 bit cpus. Also, as a last test, running lshw gives, for the cpu section:   *-cpu:0               descripción: CPU               producto: Intel(R) Core(TM)2 Duo CPU     T5800  @ 2.00GHz               fabricante: Intel Corp.               id físico: 4               información del bus: cpu@0               versión: 6.15.13               serie: 0000-06FD-0000-0000-0000-0000               ranura: U2E1               tamaño: 2GHz               capacidad: 4096MHz               anchura: 64 bits   It's in spanish and the last line stands for width (I guess register width). So... can I install the 64 bit of the OS? Will it be a big diference in performance? Because that's what I'm looking for (doesn't need to be a BIG difference)  Thanks in advance.
9952
I was trying to swap command and option key for my external keyboard following the instruction in  .  When I'm done with change and I restarted, my mac booted with Kernel panic message. I'm sure I've messed the info.plist file. Now I cannot boot in safe mode as well.  I know if I get a way to change the file it should be fine.  The message shown in screen is   panic(cpu 0 caller 0xffffff80002c4794): Kernel trap at 0xffffff80005eae1e, type 14=page fault, registers: ... Debugger called: &lt;panic&gt; Backtrace (CPU 0), Frame : Return Addressd ... ... can't perform kext scan: no kext summary BSD process name corresponding to current thread: Unknown  Mac OS version: Not yet set  Kernel version: Darwin Kernel Version 11.4.2: Thu Aug 23 16:25:48PM Kernel UUID: ... System uptime in nanoseconds: 11...   The error specifies the problem in kext as well.  Thanks.
11112
when i use NS2  through terminal i keep getting a segment fault (core dumped) message.  g_0zek@g-0zeK-pc:~$ ns lab1.tcl g_0zek@g-0zeK-pc:~$ nam lab1.nam Segmentation fault (core dumped)   despite that xgraph works ok   the code in the tcl seems ok as it was given from university and one friend of mine runs it fine.  Any ideas?
8699
How does one do this?  If I want to analyze how something is getting compiled, how would I get the emitted assembly code?
83138
If I issue the trap builtin twice [for the same signal], what happens? Is the second command added to the first, or does it replace the first?  trap Foo SIGINT ... trap Bar SIGINT ...   When SIGINT happens, does Bash just run Bar, or does it run Foo as well? Or something else...?
70480
Edit  Does the state register (the LFSR) always have to remain with 16 bits (I'm assuming yes).  If so, are we shifting the register right by one (lfsr&gt;&gt;1) and inserting the output bit onto the left-most bit (lfsr&gt;&gt;1 | bit&lt;&lt;15) which allows us to wraparound within the same 16-bit address space.  So with this in mind, how does one generate the continuous keystream given:  seed: 1100101001110101  taps: 3, 12, 14, 15    Assuming you are given the following information:  Seed: 1100101001110101  Key Fragment: 000100011110101100001101101111101  And the following ciphertext/encrypted stream: 10101011000000010010110011001100101000010101010101010111101111110111010000010011  I am seemingly unable to decrypt the entire text into some ASCII values (UTF-8 decoded). I initially wrote a Berlekamp-Massey implementation and an  to grab the tap positions of the above key fragment, which returned the following polynomial:  $$x^{15} + x^{14}+x^{12}+x^{3}+1$$  Fibonacci LFSR implemented in Rust:  fn next(&amp;mut self) -&gt; Option&lt;(u16, u16)&gt; {     self.bit = ((self.lfsr &gt;&gt; self.taps[0]) ^ (self.lfsr &gt;&gt; self.taps[1]) ^                 (self.lfsr &gt;&gt; self.taps[2]) ^ (self.lfsr &gt;&gt; self.taps[3])) &amp; 1;      self.lfsr = (self.lfsr &gt;&gt; 1) | (self.bit &lt;&lt; 15);      if self.lfsr != self.seed {         Some((self.bit, self.lfsr))     } else {         None     } }    The key fragment never appears in the generated key stream, indicating something probably went wrong. The decrypted cipher doesn't map to ASCII values, just cryptic UTF-8 symbols.   The Berlekamp-Massey implementation is based off of the following whitepaper -   And the full code can be found here -
80630
Firefox fails to update due to corrupted download (deb)  Preparing to unpack .../firefox_32.0+build1-0ubuntu0.14.04.1_i386.deb ... Unpacking firefox (32.0+build1-0ubuntu0.14.04.1) over (31.0+build1-0ubuntu0.14.04.1) ... dpkg-deb (subprocess): decompressing archive member: lzma error:  compressed data is corrupt dpkg-deb: error: subprocess &lt;decompress&gt; returned error exit status 2 dpkg: error processing archive  /var/cache/apt/archives/firefox_32.0+build1-0ubuntu0.14.04.1_i386.deb (--unpack):  cannot copy extracted data for './usr/lib/firefox/libxul.so' to '/usr/lib/firefox/libxul.so.dpkg-new':   unexpected end of file or stream Please restart all running instances of firefox, or you will experience problems.
62951
When running uname -a, I get as output   41-Ubuntu SMP Mon Aug 13 17:59:54 UTC 2012 i686 athlon i386 GNU/Linux   Can someone please explain to  me why both i386 &amp; i686 ?    What exactly is my PC architecture and what version of Ubuntu am I using (32bit or 64bit)?
56265
Boy have been asking a bunch of questions on here lately, I have always been curious about this other driver called the CPU Microcode driver, I have an intel i3 Core Processor. I understand that this will increase your CPU performance with Ubuntu pretty well, but I'm not sure if I should install it.
62297
I have recently installed  with the intention of trying it out, even though I'm not really an MMO person. Something in the game's aesthetic just really appeals to me.  While the gameplay videos I've seen looked decent, the installation experience itself had me questioning the game's credibility. The installer and subsequent launcher look slightly shady, with several suspicious windows popping up and disappearing.  When I finally got to launching the actual game, I suddenly saw the following icon before the game went full-screen:    Snooping around online, I discovered that this is some sort of cheat-prevention module called X-Trap, that is aimed to detect the following, amongst other things:        The user has modified game files   The user is running a 3rd party program that is not allowed   The user is modifying the program dynamically      While I understand why cheat prevention is important in such games, my instincts are to be highly suspicious of this module. This is exacerbated by the fact that I can't seem to find any official information about it.  So my question is, can I trust X-Trap not to:   Spy on me. Alter my computer in ways I am unaware of. Interfere with other programs. Do other bad things I can't necessarily think about.
117975
I've got a "Schroedinger's Cat" type of problem here -- my program (actually the test suite for my program, but a program nonetheless) is crashing, but only when built in release mode, and only when launched from the command line.  Through caveman debugging (ie, nasty printf() messages all over the place), I have determined the test method where the code is crashing, though unfortunately the actual crash seems to happen in some destructor, since the last trace messages I see are in other destructors which execute cleanly.  When I attempt to run this program inside of Visual Studio, it doesn't crash.  Same goes when launching from WinDbg.exe.  The crash only occurs when launching from the command line.  This is happening under Windows Vista, btw, and unfortunately I don't have access to an XP machine right now to test on.  It would be really nice if I could get Windows to print out a stack trace, or something other than simply terminating the program as if it had exited cleanly.  Does anyone have any advice as to how I could get some more meaningful information here and hopefully fix this bug?  Edit: The problem was indeed caused by an out-of-bounds array, .  Thanks everybody for your help in finding this problem!
29762
What is "preimage resistance", and how can the lack thereof be exploited? How is this different from collision resistance, and are there any known preimage attacks that would be considered feasible?