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Re: GDB infinite loop when stepping on "while (1) i++;"
Hi,
On Thu, 2007-03-22 at 15:44 +0800, qinwei wrote:
> Dears, problems are here:
>
> gcc -o t -gdwarf-2 tp_while1.c
> gdb t
> (gdb) b main
> Breakpoint 1 at 0x8048350: file tp_while1.c, line 3.
> (gdb) r
> Starting program: /home/qinwei/GJ283/code/build_linux/debug-gdb/t
>
> Breakpoint 1, main () at tp_while1.c:3
> 3 int i = 10;
> (gdb) n
> 4 while (1) i++;
> (gdb) n
>
> When program stops at "while (1) i++;", and printing "next" command will
> cause gdb infinite loop.
> The target are x86, score, or other? (gdb-6.6 release version)
>
> Is the reason that the following dwarf-2 info:
>
> "Special opcode 104: advance Address by 7 to 0x8048357 and Line by 1 to
> 4"
> "Advance PC by 7 to 804835e"
>
> which makes "while (1)" and "i++;" the same line number? And gdb will get
> "stop_pc" from the range [0x8048357, 0x804835e] and will not stop?
Yes. The command `next' is used to move to advance execution to the next
line of the current function.
> How to solve it? Thanks!
Try using `nexti' of `stepi'.
Cheers,
Kunal
>
> int main (void)
> {
> int i = 10;
> while (1) i++;
> return 0;
> }
>
> Line Number Statements:
> Extended opcode 2: set Address to 0x8048334
> Special opcode 6: advance Address by 0 to 0x8048334 and Line by 1 to 2
> Advance PC by constant 17 to 0x8048345
> Special opcode 160: advance Address by 11 to 0x8048350 and Line by 1 to
> 3
> Special opcode 104: advance Address by 7 to 0x8048357 and Line by 1 to 4
> Advance PC by 7 to 804835e
> Extended opcode 1: End of Sequence
>
> 08048334 <main>:
> 8048334: 55 push %ebp
> 8048335: 89 e5 mov %esp,%ebp
> 8048337: 83 ec 08 sub $0x8,%esp
> 804833a: 83 e4 f0 and $0xfffffff0,%esp
> 804833d: b8 00 00 00 00 mov $0x0,%eax
> 8048342: 83 c0 0f add $0xf,%eax
> 8048345: 83 c0 0f add $0xf,%eax
> 8048348: c1 e8 04 shr $0x4,%eax
> 804834b: c1 e0 04 shl $0x4,%eax
> 804834e: 29 c4 sub %eax,%esp
> 8048350: c7 45 fc 0a 00 00 00 movl $0xa,0xfffffffc(%ebp)
> 8048357: 8d 45 fc lea 0xfffffffc(%ebp),%eax
> 804835a: ff 00 incl (%eax)
> 804835c: eb f9 jmp 8048357 <main+0x23>
> 804835e: 90 nop
> 804835f: 90 nop
>
> Best regards,
> Qinwei
> Mail qinwei@sunnorth.com.cn
> Phone +86-010-62981668-2708
> Fax +86-010-62985972
--
Kunal Parmar
Tools Team,
Celunite Inc. (www.celunite.com)