Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <pre><code>#include &lt;stdio.h&gt; int main(int argc, char **argv) { char c[] = "a"; printf("%d\n", *(int*)(c)); } </code></pre> <p>This gives me a <a href="http://en.wikipedia.org/wiki/SIGBUS" rel="nofollow noreferrer">SIGBUS</a> after setting <code>set $ps |= (1&lt;&lt;18)</code> in gdb, which apparently is thrown when address alignment is incorrect (amongst other reasons).</p> <p>EDIT: It's fairly easy to raise SIGBUS:</p> <pre><code>int main(int argc, char **argv) { /* EDIT: enable AC check */ asm("pushf; " "orl $(1&lt;&lt;18), (%esp); " "popf;"); char c[] = "1234567"; char d[] = "12345678"; return 0; } </code></pre> <p>Looking at main's disassembly in gdb:</p> <pre><code>Dump of assembler code for function main: .... 0x08048406 &lt;main+34&gt;: mov 0x8048510,%eax 0x0804840b &lt;main+39&gt;: mov 0x8048514,%edx 0x08048411 &lt;main+45&gt;: mov %eax,-0x10(%ebp) 0x08048414 &lt;main+48&gt;: mov %edx,-0xc(%ebp) 0x08048417 &lt;main+51&gt;: movl $0x34333231,-0x19(%ebp) &lt;== BAM! SIGBUS 0x0804841e &lt;main+58&gt;: movl $0x38373635,-0x15(%ebp) 0x08048425 &lt;main+65&gt;: movb $0x0,-0x11(%ebp) </code></pre> <p>Anyhow, Christoph your test program fails under Linux raising a SIGBUS as it should. It's probably a Windows thing?</p> <hr> <p>You can enable the Alignment Check bit in code using this snippet:</p> <pre><code>/* enable AC check */ asm("pushf; " "orl $(1&lt;&lt;18), (%esp); " "popf;"); </code></pre> <p>Also, ensure that the flag was indeed set:</p> <pre><code>unsigned int flags; asm("pushf; " "movl (%%esp), %0; " "popf; " : "=r"(flags)); fprintf(stderr, "%d\n", flags &amp; (1&lt;&lt;18)); </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POMis-aligned pointers on x86
      singulars
      1. PTQuestion
    1. PTAnswer
    1. UScodelogic
    1. UScodelogic
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI fail to reproduce this with gcc (GCC) 3.4.5 (mingw-vista special r3), I'll try later with a different version...
      singulars
      1. PO
      1. USChristoph
    2. COThis was compiled with gcc 4.3.2 running kernel 2.6.27 on an Intel Core 2 Duo.
      singulars
      1. PO
      1. UScodelogic
    3. COAlso, it doesn't throw a SIGBUS without setting the flag you mentioned.
      singulars
      1. PO
      1. UScodelogic
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload