Windows hosted GDB hang at breaking point

[Joey Ye]

Host: Only happens on Windows
Version: 4.7
When debugging following program and break point test with Windows hosted GDB and certain version of gdbserver from 3rd party, it just hangs.

unsigned char test(unsigned char c)
{
    return (c + 2);
}

int main(void)
{
   unsigned char temp;
   temp = test(1);
   temp = test(0x50);
   temp = test(0x90);
    while(1)
    {
    }
}

[Joey Ye (jinyun-ye)]

From Terry:

This issue is against gcc 4.7 and gdb 7.4. At this time the dwarf info generated by gcc doesn't meet the requirement of gdb. So when gdb stops at function test, it calculated a wrong value for function argument c based on incomplete dwarf info. Then gdb calls iconv to translate argument c's immediate value into some kind of character for a better reading. Unfortunately we are using libiconv 1.11 which has bug code in function wchar_to_loop_convert, when c's value meets some conditions like too big, this function will fall into an endless while loop. From gdb user's perspective, it looks like gdb is halted at function break point.

The latest libiconv 1.14 fixed its bug. After building tool chain with 1.14, this issue disappears.

The iconv function for Linux-based tool chain comes from glibc which has its own implementation. So far no such issue for Linux-based tool chain.