here need your help

Subprojects LLDB
1

hi all ,
This is amiko who is a new lldb user ,There is same questions need your help
1, Can lldb debug C/C++ project .ext file directly like gdb or not ?
2 ,Here is a simple c project named helloword the detail source please follow below:

// helloworld.c
1 #include <stdio.h>
2 int main()
3 {
4 int i ;
5 for(i=0 ;i<2;i++)
6 {
7 printf (“hello world\n”);
8 }
9 return 0 ;
10 }
my step is
1 clang -g -o helloworld helloworld.c
2 $lldb helloworld
3 b hellowold.c:7
4 run
I think it will pause in line 7 .however it seems fail ,and print two hello world , In other word setting breakpoint operation does not useful . Is any error or fault for my operations ,Thank you very much ,And looking forward to your reply ,Thanks again .

2

Do you get any output from lldb upon setting the breakpoint?
That would be a first step. You can also issue a breakpoint list command to check all breakpoints and see if they resolved correctly.

Enrico Granata <egranata@🍎.com>

3

You did everything correctly. My guess is you didn't supply -O0 on your compile line and the compiler optimized your code. When the compiler optimizes your code, the line numbers and debug info are not very useful due the the optimizations.

Try compiling with:

% clang -g -O0 -o helloworld helloworld.c

And try again.

Greg

4

Thank you very much ,And i have tried it on my computer ,however ,it seems fail too ,what’s more , As the llvm offical web site ,it seems support X86_64 not x86_32 ,For my Operation Systerm is ubuntu x86_32 , And i also try in ubuntu x86_64 ,And it success , it is my fail reason ? Thank your much ! And looking forward to your reply .

5

I am not sure why x86_32 would fail as I have never dealt with that platform. I know that when we set a breakpoint in the debuggee, we put a "INT" instruction (0xcc) into the program. I am not sure if x86_32 does anything differently with the 0xcc traps.

You might try and place a:

__builtin_trap()

into your code:

#include <stdio.h>
int main()
{
    for(int i=0 ;i<2;i++)
    {
        printf ("hello world\n");
    }
    __builtin_trap();
    return 0;
}

then compile and debug it. If the debugger stops at the builtin_trap, then at least we know the breakpoint opcode should trigger the process to stop.

% clang -g -O0 -o helloworld helloworld.c
% lldb helloworld
The other thing you can do is attach the output of the following commands:

(lldb) b helloworld.c:7
(lldb) b
(lldb) target list

I might be able to tell more if you attach the output to the LLDB commands above...

Greg