Host based simulator doesn't like my new code

[Traumflug]

Look like the simulator doesn'T like the code I just committed onto the cross branch:

$ gdb --args ./sim testcases/straight-speeds.gcode --tracefile=straight.trace --time-scale=0 --gcode 
[...]
(gdb) run
Starting program: /home/mah/RepRap/Teacup_Firmware/./sim testcases/straight-speeds.gcode --tracefile=straight.trace --time-scale=0 --gcode
timer_init: warp-speed
opening testcases/straight-speeds.gcode
analog_init: not implemented in simulator
start
ok
[...] 
G90
ok 
ok 
G1 X5 F400
ok 

Program received signal SIGSEGV, Segmentation fault.
[...]
(gdb) bt
#0  0x000000000040146d in dda_create (dda=0x608388 <movebuffer+104>, target=target@entry=0x6089b8 <next_target+8>) at dda.c:94
#1  0x00000000004024d9 in enqueue_home (t=0x6089b8 <next_target+8>, endstop_check=<optimized out>, 
    endstop_stop_cond=<optimized out>) at dda_queue.c:124
#2  0x000000000040310c in enqueue (t=<optimized out>) at dda_queue.h:36
#3  process_gcode_command () at gcode_process.c:626
#4  0x0000000000402a78 in gcode_parse_char (c=240 '\360') at gcode_parse.c:351
#5  0x0000000000400fa2 in main (argc=<optimized out>, argv=<optimized out>) at mendel.c:258
(gdb) list
89    #ifdef LOOKAHEAD
90    // Number the moves to identify them; allowed to overflow.
91    static uint8_t idcnt = 0;
92    static DDA* prev_dda = NULL;
93  
94    if (prev_dda->done || dda->waitfor_temp)
95      prev_dda = NULL;
96    #endif
97  
98    if (dda->waitfor_temp)
(gdb) 

[phord]

It bisects to here:

commit 315a081ee89a15388bf82695fa05faf3690bc017
Author: Markus Hitter <mah@jump-ing.de>
Date:   Wed Nov 27 18:50:37 2013 +0100

gcode_parse.c: assume G1 only for stuff which might actually move.

Previously, even comments were run through dda_create(), quite a waste
of time.

[phord]

Reverting that commit doesn't fix it. Investigating...

[phord]

Fixed. The code in 03631ce10c2875c99b1d5489cfdb4bc2d6abad7b dereferenced NULL, but AVR didn't notice:

static DDA* prev_dda = NULL;
if (prev_dda->done)
  prev_dda = NULL;