Wireshark-bugs: [Wireshark-bugs] [Bug 11122] "Export packet dissections > As plain text" crashed
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From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Fri, 17 Apr 2015 08:25:17 +0000

Comment # 8 on bug 11122 from 
(In reply to Ralf G. R. Bergs from comment #7)
> (In reply to Guy Harris from comment #5)
> 
> > Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
> > Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000008
> > 
> > which means "null pointer dereference"
> 
> Please note the address is 0x0000000000000008 (eight) -- so NOT a null
> pointer deref?
> 
> Sorry if this is B/S, I haven't programmed in C since 20 years... :-)

struct foo {
    char *p;
    char *q;
};

    ...

    struct foo *r = NULL;

        ...

    if (r->q == NULL)
        printf("It's null\n");

is dereferencing a null pointer, but, on an LP64 or LLP64 platform with the
page at address 0 mapped out (and with a null pointer having all its bits
clear, which isn't a requirement of C or C++), it will crash trying to fetch a
pointer at an address of 0x0000000000000008.

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