Re: Including <iostream> affects whether or not program freezes?

["James Gregory" <james.jrg@gmail.com>]

On Wed, Jul 9, 2008 at 5:49 PM, Chris Jefferson <chris@bubblescope.net> wrote:
> 2008/7/9 James Gregory <james.jrg@gmail.com>:

>> 4. Compile with gcc 4.2.3 (Ubuntu 64 bit), with optimization: my
>> program freezes in a particular function
>> 5. Compile with gcc 4.2.3 (Ubuntu 64 bit), with optimization, and
>> include <iostream> at the top of the file where the function which
>> freezes is defined: my program doesn't freeze

Chris Jefferson suggested I add the compiler flag "-fdump-tree-all". I
did this for the build which included iostream and the one which
didn't, produced a diff of the final code produced for the problematic
source file between each version, cropped it a bit, and came up with
the following. I don't understand assembler, but the header file
inclusion has clearly changed the code gcc produces. The obvious
differences are:

1. The existence of the line "-Invalid sum of incoming frequencies
873, should be 0" in the freezing version
2. The replacement of this in the version which freezes:

-  const unsigned char * this___l_iterthis__I___M_currentthis____.4618;
-  const unsigned char * this___l_iterthis__I___M_currentthis____.4617;
-  const unsigned char * this___l_iterthis__I___M_currentthis____.4616;

to this in the version which doesn't:

+  unsigned char temp.4650;
+  unsigned char temp.4649;
+  unsigned char temp.4648;

Can anyone tell me what is going on here?

--- AIInterpreter.cpp.102t.final_cleanup	2008-07-12 21:21:37.000000000 +0100
+++ ../nofreeze/AIInterpreter.cpp.102t.final_cleanup	2008-07-12
21:23:33.000000000 +0100

<snip>

 bool AIInterpreter::is_group_like_this(int, int, bool, bool) (this,
n_side, n_group, discount_dead, discount_our)
 {
-  int stat_value.4637;
-  const unsigned char * this___l_iterthis__I___M_currentthis____.4618;
-  const unsigned char * this___l_iterthis__I___M_currentthis____.4617;
-  const unsigned char * this___l_iterthis__I___M_currentthis____.4616;
+  int stat_value.4653;
+  unsigned char temp.4650;
+  unsigned char temp.4649;
+  unsigned char temp.4648;
   int give_group;
   int give_side;
-  struct Group_Base * D.100623;
-  bool D.100627;
+  struct Group_Base * D.100677;
+  bool D.100681;
   size_t __n;
-  struct Group_Base * D.100588;
-  const unsigned char * D.86283;
-  const unsigned char & D.86265;
-  unsigned char D.86266;
-  const unsigned char & D.86197;
-  unsigned char D.86198;
-  const unsigned char & D.86143;
-  unsigned char D.86144;
+  struct Group_Base * D.100642;
+  const unsigned char * D.86304;
+  const unsigned char & D.86286;
+  unsigned char D.86287;
+  const unsigned char * D.86270;
+  const unsigned char & D.86218;
+  unsigned char D.86219;
+  const unsigned char * D.86202;
+  const unsigned char & D.86164;
+  unsigned char D.86165;
+  const unsigned char * D.86148;
   size_t __n;
-  struct Side * D.86086;
+  struct Side * D.86107;
   int second_value;
   const unsigned char operator_type;
   int stat_value;
-  const unsigned char & D.68774;
-  unsigned char D.68755;
-  int D.68741;
+  const unsigned char & D.68792;
+  unsigned char D.68773;
+  int D.68759;

 <bb 2>:
-  D.100588 = operator-> (&((sides.D.66353._M_impl._M_start + (struct
Side *) ((long unsigned int) n_side *
256))->groups.D.33422._M_impl._M_start + (struct Group *) ((long
unsigned int) n_group * 16))->h_group);
-  if (D.100588->alive) goto <L1>; else goto <L0>;
+  D.100642 = operator-> (&((sides.D.66353._M_impl._M_start + (struct
Side *) ((long unsigned int) n_side *
256))->groups.D.33422._M_impl._M_start + (struct Group *) ((long
unsigned int) n_group * 16))->h_group);
+  if (D.100642->alive) goto <L1>; else goto <L0>;

 <L0>:;
   if (discount_dead) goto <L8>; else goto <L1>;
@@ -6385,72 +6402,70 @@
 <L1>:;
   __n = (long unsigned int) n_group;
   __n = (long unsigned int) n_side;
-  D.86086 = sides.D.66353._M_impl._M_start;
-  if ((*(((D.86086 + (struct Side *) ((long unsigned int)
this->my_side * 256))->scanned_groups.D.34444._M_impl._M_start +
(struct vector<bool,std::allocator<bool> > *) (__n *
40))->D.67000._M_impl._M_start.D.26400._M_p + (_Bit_type *) ((__n >>
6) * 8)) & 1 << (int) ((unsigned int) __n & 63)) == 0) goto <L8>; else
goto <L2>;
+  D.86107 = sides.D.66353._M_impl._M_start;
+  if ((*(((D.86107 + (struct Side *) ((long unsigned int)
this->my_side * 256))->scanned_groups.D.34444._M_impl._M_start +
(struct vector<bool,std::allocator<bool> > *) (__n *
40))->D.67000._M_impl._M_start.D.26400._M_p + (_Bit_type *) ((__n >>
6) * 8)) & 1 << (int) ((unsigned int) __n & 63)) == 0) goto <L8>; else
goto <L2>;

 <L2>:;
-  D.100623 = operator-> (&((D.86086 + (struct Side *) (__n *
256))->groups.D.33422._M_impl._M_start + (struct Group *) (__n *
16))->h_group);
-  D.100627 = OBJ_TYPE_REF(*(D.100623->_vptr.Group_Base +
152B);D.100623->19) (D.100623);
-  if (D.100627 != 0) goto <L8>; else goto <L3>;
+  D.100677 = operator-> (&((D.86107 + (struct Side *) (__n *
256))->groups.D.33422._M_impl._M_start + (struct Group *) (__n *
16))->h_group);
+  D.100681 = OBJ_TYPE_REF(*(D.100677->_vptr.Group_Base +
152B);D.100677->19) (D.100677);
+  if (D.100681 != 0) goto <L8>; else goto <L3>;

 <L3>:;
-  if (this->my_side != n_side) goto <L160>; else goto <L4>;
+  if (this->my_side != n_side) goto <L163>; else goto <L4>;

 <L4>:;
-  if (this->my_group != n_group) goto <L160>; else goto <L5>;
+  if (this->my_group != n_group) goto <L163>; else goto <L5>;

 <L5>:;
-  if (discount_our) goto <L8>; else goto <L160>;
+  if (discount_our) goto <L8>; else goto <L163>;

 <L8>:;
-  D.86143 = this->l_iter._M_current;
-  if (D.86143 == this->l_end._M_current) goto <L36>; else goto <L103>;
+  D.86164 = this->l_iter._M_current;
+  if (D.86164 == this->l_end._M_current) goto <L36>; else goto <L103>;

 <L103>:;
-  D.86144 = *D.86143;
-  if (D.86144 == 157) goto <L36>; else goto <L104>;
+  temp.4648 = *D.86164;
+  if (temp.4648 == 157) goto <L36>; else goto <L104>;

 <L104>:;
-  if (D.86144 == 158) goto <L36>; else goto <L120>;
+  if (temp.4648 == 158) goto <L36>; else goto <L166>;

-<L120>:;
-  this___l_iterthis__I___M_currentthis____.4616 = (const unsigned
char *) ((long unsigned int) D.86143 + 1);
+<L39>:;
+  D.86165 = *D.86148;
+  if (D.86165 == 157) goto <L36>; else goto <L40>;

-Invalid sum of incoming frequencies 873, should be 0
 <L40>:;
-  this___l_iterthis__I___M_currentthis____.4616 = (const unsigned
char *) ((long unsigned int)
this___l_iterthis__I___M_currentthis____.4616 + 1);
-  if (D.86144 == 157) goto <L162>; else goto <L40>;
+  if (D.86165 == 158) goto <L36>; else goto <L166>;

-Invalid sum of incoming frequencies 0, should be 301
-<L162>:;
-  this->l_iter._M_current = this___l_iterthis__I___M_currentthis____.4616;
-  D.68741 = 0;
-  goto <bb 42> (<L174>);
+<L166>:;
+  D.86148 = this->l_iter._M_current + 1B;
+  this->l_iter._M_current = D.86148;
+  if (this->l_end._M_current == D.86148) goto <L36>; else goto <L39>;

<snip>

James