auto_index crashes during boostbook xml processing

[alexey kutumov <alexey.kutumov@…>]

auto_index crashes with following backtrace:

#3 0x08126947 in std::pair<std::string, std::string>::pair (this=0xbf909bb8, a=<error reading variable: Cannot access memory at address 0x0>, b="end")

at /usr/include/c++/4.7/bits/stl_pair.h:105

#4 0x0811ef7c in process_node (node=..., prev=0xbf909ea4, pt=0xbf909e9c, seen=false)

at /usr/src/projects/boost/modularize/src/boost/auto_index/src/auto_index.cpp:469

I founded, that this error happens when we construct item_index:

std::pair<std::string, std::string> item_index(*pid, i->term);

with incorrect pid argument (in this case it equals to zero). This variable is initialized at line 455:

const std::string* pid = get_current_block_id(&id);

And this function returns 0, which causes segfault

[alexey kutumov <alexey.kutumov@…>]

reproducing example

[John Maddock]

You can't run auto_index on boostbook, only on docbook.

[Steven Watanabe]

Even if it's illegal, auto_index shouldn't crash on invalid input.

[John Maddock]

(In [83952]) Throw exception on precondition failure. Fixes #7967.