>Isn't Signal 11 typically a symtom of bad memory, i/o timing, or other
>hardware flakiness?
It's typically a software engineering boo-boo, as in:
Segmentation Fault (Segmentation Violation (SEGV) - Signal 11)
The program attempts to write to a region of memory to which it does not
have access. Is typically a pointer usage problem, as in the following:
- Writing past the end of an array (table): "subscript out of range".
- Attempting to store into a string literal, as in:
string = "abcde"; *(string + 1) = 'B';
Note that string literals are contained in the Application Program
Text area of the address space, which is read-only.
- Using an uninitialized pointer.
- Using no indirection where indirection (&something) is required, or
single indirection where double indirection is required. A common
error is passing a struct_name instead of &struct_name.
- The destination of sscanf being specified as the object itself (such
as an int) rather than the address of it.
- In "printf(%s)" for an int value, which instead wants "printf(%d)".
- In "printf(%s)", no variable supplied for the value, or too few
variables coded.
- In computing a position within a table, using just the offset value
rather than table base address plus offset.
- Your code attempts to modify a read-only string literal.
This problem can sometimes be caused by defective libraries, as in
needing to upgrade to the latest libc.
In occasional instances, giving a program more memory *might* help.
Note that dereferencing a zeroed pointer will not result in a
Segmentation Fault in AIX: IBM carried on the mainframe tradition of
having low virtual memory map to the nucleus (kernel). See "Address
Space".
Richard Sims, BU
