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digitalmars.D.bugs - [Issue 3214] New: Incorrect DWARF line number debugging information on Linux

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3214

           Summary: Incorrect DWARF line number debugging information on
                    Linux
           Product: D
           Version: 1.046
          Platform: x86
        OS/Version: Linux
            Status: NEW
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: nfxjfg gmail.com


Here's an example that shows that dmd obviously/probably generates incorrect
DWARF line number debugging information under Linux. The example consists of
several modules, and I don't know if it's further reducible, or where the
problem actually is. (I'm happy that's it's reproducible at all.)

a.d >>>
module a;

import b;

void main(char[][] args) {
    throw new Exception("huh");
}
<<<

b.d >>>
module b;

import c;

void foo1() {
}
<<<

c.d >>>
module c;

class Foo2 : Exception {
    this() {
        super("huh");
    }
}
<<<

Compile exactly like this:
  dmd -c a.d b.d c.d -od. -g
  dmd  a.o b.o c.o  -ofa -g

Now look what is wrong and check if the symbol "_D1c4Foo25_ctorMFZC1c4Foo2" is
correct:

1. Get address:
  nm a|grep _D1c4Foo25_ctorMFZC1c4Foo2 |cut -f2 -d: | cut -f1 -d' '
(outputs something like "08049b64")
2. Resolve the address:
  addr2line -e a 0x08049b64

This outputs "/tmp/test/xx/b.d:5", although the symbol is in c.d. Somehow, the
address is incorrectly resolved, which suggests that the compiler might
generate incorrect debugging information.

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--- Comment #1 from nfxjfg gmail.com  2009-07-29 21:19:56 PDT ---
Created an attachment (id=435)
 --> (http://d.puremagic.com/issues/attachment.cgi?id=435)
dmd patch to fix the problem (against dmd 1.046)

I think I found out why it doesn't work: when compiling several files at once,
the object writer's state isn't reset correctly. Now I don't know how the hell
the backend works; I just noticed that the DWARF writer still tried to write
line numbers from the previous file (also notice what's added by objlinnum()).
In this case, c.o contained some line number information from b.o, which is why
addr2line resolved the address mentioned to b.d.

I'm posting a trivial 3 line patch that seems to solve the problem. It simply
makes obj_init() forget about the SegData from the previous object file. I
don't know if it's correct or complete, but with my test cases (the one posted
above and a larger, non-trivial heap of code) it seemed to work very well. The
patch causes a little memory leak, but that'd trivial to fix (maybe not setting
seg_max to 0 does it).

There's just one more problem. When resolving some invalid address with
addr2line, I get this output:

BFD: Dwarf Error: mangled line number section (bad file number).
BFD: Dwarf Error: mangled line number section (bad file number).
BFD: Dwarf Error: Could not find abbrev number 1014.
BFD: Dwarf Error: Could not find abbrev number 119.
BFD: Dwarf Error: Could not find abbrev number 651.
BFD: Dwarf Error: Could not find abbrev number 53.
BFD: Dwarf Error: Could not find abbrev number 84.
BFD: Dwarf Error: Could not find abbrev number 657.
BFD: Dwarf Error: Could not find abbrev number 1230.

I have no idea what's up with that and I can't reproduce it with a simpler
testcase.

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Robert Clipsham <robert octarineparrot.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
                 CC|                            |robert octarineparrot.com


--- Comment #2 from Robert Clipsham <robert octarineparrot.com> 2009-09-08
05:49:22 PDT ---
Don't forget to add the patch keyword along with the patch so it doesn't get
missed :)

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nfxjfg gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Depends on|                            |3540


--- Comment #3 from nfxjfg gmail.com 2009-11-21 18:28:15 PST ---
Also see 3540.

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--- Comment #4 from nfxjfg gmail.com 2009-11-22 21:40:49 PST ---
Problem still persists in dmd 1.051 and the dmd svn version (as of revision
267).

I assume there is some other problem, that doesn't make fixing the bug as
simple as it seems?

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--- Comment #5 from nfxjfg gmail.com 2010-04-01 05:58:19 PDT ---
It's strange...
With my patch, my executable has a size of 16 MB, with a .debug_line section
size of ca. 500 KB.
Without my patch, it's 32 MB, of which .debug_line takes up 16 MB.

PS:

With the fix for bug 3987, the addr2line error messages go away (when compiling
with -gc).
Which means my patch doesn't cause additional problems at least in this aspect.

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nfxjfg gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX


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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Brad Roberts <braddr puremagic.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |braddr puremagic.com
         Resolution|WONTFIX                     |


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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
                 CC|                            |bugzilla digitalmars.com
         Resolution|                            |FIXED


--- Comment #6 from Walter Bright <bugzilla digitalmars.com> 2011-04-04
12:36:33 PDT ---
https://github.com/D-Programming-Language/dmd/commit/01aab6459cfba2eb85feb1481c01c17b8a3badfe

https://github.com/D-Programming-Language/dmd/commit/5f1a6afb1363fe950d2392748fc35f5914c6c6f5

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