_IO_wide_data_2: what's this?

Question

I'm working on an embedded platform (architecture is SH4), and my program crashed a few minutes ago with a SIGABRT.

Luckily, I was running under gdbserver, and the thread that was interrupted by this signal has this stack dump:

#0  0x2a7f1678 in raise () from /home/[user]/target/lib/libc.so.6
#1  0x2a7f2a4c in abort () from /home/[user]/target/lib/libc.so.6
#2  0x2a81ade0 in __libc_message () from /home/[user]/target/lib/libc.so.6
#3  0x2a81f3a8 in malloc_printerr () from /home/[user]/target/lib/libc.so.6
#4  0x2a8c3700 in _IO_wide_data_2 () from /home/[user]/target/lib/libc.so.6

Do you know what happened here? A bad free()? bad delete ? bad malloc? What's "_IO_wide_data_2" supposed to do? I see the malloc_printerr() call that I don't understand either.

Google gives me 234 results on this, but all of them are simply because the guys have that "function" in their backtrace.

Answer 1

It is a stream to stderr for wide character support.

You can break it down into various parts:

• _IO : Input/Output.
• wide_data : Wide data
• 2 : stderr

You also have;

_IO_wide_data_0 : stdin _IO_wide_data_1 : stdout

They are chained as 2->1->0.

malloc_printerr() is used to print various error messages when there is something bad happening/caught in dynamic memory management. But your trace looks capped (have you removed anything?).

It could be a write to stderr where you try to write something not in memory, in corrupted memory, in …

Or it could be lower stack point causing write to stderr.

Or …