Debugging with GDB Manual (5900-1473; WDB 6.2; January 2011)

((gdb)) whatis g
type = double
((gdb)) p g
$1 = 1
((gdb)) set g=4
((gdb)) p g
$2 = 1
((gdb)) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/smith/cc_progs/a.out
"/home/smith/cc_progs/a.out": can't open to read symbols:
Invalid bfd target.
((gdb)) show g
The current BFD target is "=4".
The steps shown above sets the gnutarget to an invalid value in place of the program
variable g.
In order to set the variable g, use
((gdb)) set var g=4
GDB allows more implicit conversions in assignments than C; you can freely store an
integer value into a pointer variable or vice versa, and you can convert any structure to
any other structure that is the same length or shorter.
To store values into arbitrary places in memory, use the '{...}' construct to generate
a value of specified type at a specified address (see“Expressions” (page 76)). For
example, {int}0x83040 refers to memory location 0x83040 as an integer (which
implies a certain size and representation in memory), and
set {int}0x83040 = 4
stores the value 4 into that memory location.
11.2 Continuing at a different address
Ordinarily, when you continue your program, you do so at the place where it stopped,
with the continue command. You can continue at a selected address using one of the
following commands:
jump linespec Resume execution at line linespec. Execution stops again
immediately if there is a breakpoint there. See “Printing source
lines” (page 71), for a description of the different forms of
linespec. It is common practice to use the tbreak command
in conjunction with jump. See “Breakpoints” (page 46).
The jump command does not change the current stack frame, the
stack pointer, the contents of any memory location or any register
other than the program counter. If line linespec is in a different
114 Altering Execution