[cfe-dev] Debug information on multiple files

[Renato Golin]

Hi,

I'm trying to compile two files together with debug information but
seems that LLVM is getting the DW_AT_stmt_list wrong when ld is
linking the final executable.

Originally, I tried on ARM with Clang (+llc+gas+ln) and, the object
files, the DW_AT_stmt_list were null, as expected. When linking, they
should point to the offset in the line table, but all of them are
still null, so pointing all to the same line table (whichever object
gets linked first).

I then tested with SVN Clang+LLVM and got the same problem for x86-64.
In GDB, when you're stepping through the program, whichever file got
linked first has line information and you can only step on the source
of the first object.

My Files:

-------------------------------- ext.c
#include <stdio.h>

int external_fn(void)
{
  int i;
  for (i = 0; i < 5; ++i) {
    printf("ext fn #%d\n", i);
  }
  return 0;
}

-------------------------------- main.c
#include <stdio.h>

int external_fn(void);

int main(int argc, char** argv)
{
  printf("TestMsg\n");
  external_fn();
  return 0;
}

$ clang -g main.c ext.c
$ gdb -q a.out
(gdb) start
Temporary breakpoint 1 at 0x4004c0: file main.c, line 7.
Starting program: /work/temp/a.out

Temporary breakpoint 1, main (argc=1, argv=0x7fffffffbf18) at main.c:7
7         printf("TestMsg\n");
(gdb) n
TestMsg
8         external_fn();
(gdb) s
ext fn #0
ext fn #1
ext fn #2
ext fn #3
ext fn #4
9         return 0;
(gdb)

If I compile ext.c first, main has no line information:

$ clang -g ext.c main.c
$ gdb a.out
(gdb) start
Temporary breakpoint 1 at 0x4004e4
Starting program: /work/temp/a.out

Temporary breakpoint 1, 0x00000000004004e4 in main (argc=0, argv=0x7fffffffbf10)
(gdb) n
Single stepping until exit from function main,
which has no line number information.
TestMsg
ext fn #0
ext fn #1
ext fn #2
ext fn #3
ext fn #4
0x00000033c5e1d974 in __libc_start_main () from /lib64/libc.so.6
(gdb)


What am I missing?

-- 
cheers,
--renato

http://systemcall.org/

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