Re: Using libbacktrace in libgfortran: some questions

[Ian Lance Taylor]

On Thu, Aug 13, 2015 at 8:25 AM, Ian Lance Taylor <i...@google.com> wrote:
> On Thu, Aug 13, 2015 at 7:11 AM, FX <fxcoud...@gmail.com> wrote:
>>
>>> I don't know why this is not working.  Everything looks fine in the
>>> a.out that you sent.  Unfortunately, I think you sent the one built
>>> without libbacktrace.  Can you send me the one built with libbacktrace?
>>
>> Attached is the a.out with libgfortran (and thus libbacktrace) linked in 
>> statically. If this isn’t sufficient, I can send any file necessary 
>> (including the whole tree if need be).
>
> Thanks.  The problem seems to be that gfortran is generating DWARF
> info that looks like this:
>
> subprogram test
>   subprogram foo
>   subprogram bar
>
> libbacktrace does not expect to see this structure, and it thinks that
> foo and bar have been inlined within test, which is not the case.
>
> Please try this patch to libbacktrace and see if it helps.

And yet, that patch has absolutely nothing to do with libbacktrace.
Hmmm.  Let's try this one.

Ian

Index: dwarf.c
===================================================================
--- dwarf.c     (revision 226846)
+++ dwarf.c     (working copy)
@@ -2250,7 +2250,8 @@ read_function_entry (struct backtrace_st
                     struct unit *u, uint64_t base, struct dwarf_buf *unit_buf,
                     const struct line_header *lhdr,
                     backtrace_error_callback error_callback, void *data,
-                    struct function_vector *vec)
+                    struct function_vector *vec_function,
+                    struct function_vector *vec_inlined)
 {
   while (unit_buf->left > 0)
     {
@@ -2258,6 +2259,7 @@ read_function_entry (struct backtrace_st
       const struct abbrev *abbrev;
       int is_function;
       struct function *function;
+      struct function_vector *vec;
       size_t i;
       uint64_t lowpc;
       int have_lowpc;
@@ -2279,6 +2281,11 @@ read_function_entry (struct backtrace_st
                     || abbrev->tag == DW_TAG_entry_point
                     || abbrev->tag == DW_TAG_inlined_subroutine);
 
+      if (abbrev->tag == DW_TAG_inlined_subroutine)
+       vec = vec_inlined;
+      else
+       vec = vec_function;
+
       function = NULL;
       if (is_function)
        {
@@ -2458,7 +2465,8 @@ read_function_entry (struct backtrace_st
          if (!is_function)
            {
              if (!read_function_entry (state, ddata, u, base, unit_buf, lhdr,
-                                       error_callback, data, vec))
+                                       error_callback, data, vec_function,
+                                       vec_inlined))
                return 0;
            }
          else
@@ -2471,7 +2479,8 @@ read_function_entry (struct backtrace_st
              memset (&fvec, 0, sizeof fvec);
 
              if (!read_function_entry (state, ddata, u, base, unit_buf, lhdr,
-                                       error_callback, data, &fvec))
+                                       error_callback, data, vec_function,
+                                       &fvec))
                return 0;
 
              if (fvec.count > 0)
@@ -2535,7 +2544,7 @@ read_function_info (struct backtrace_sta
   while (unit_buf.left > 0)
     {
       if (!read_function_entry (state, ddata, u, 0, &unit_buf, lhdr,
-                               error_callback, data, pfvec))
+                               error_callback, data, pfvec, pfvec))
        return;
     }