[Bug default/24274] New: low-mem files processed in multifile mode

[Bug default/24274] New: low-mem files processed in multifile mode

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=24274

            Bug ID: 24274
           Summary: low-mem files processed in multifile mode
           Product: dwz
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: default
          Assignee: nobody at sourceware dot org
          Reporter: vries at gcc dot gnu.org
                CC: dwz at sourceware dot org
  Target Milestone: ---

Consider four executables, a.out and b.out a hello world example, and c.out and
d.out copied from the dwz executable itself:
...
$ gcc hello.c -g ; cp a.out b.out
$ cp dwz c.out ; cp c.out d.out
...

This gives us two executables with 130 DIEs, and two executables with 5356
DIEs:
...
$ readelf -w a.out | grep '(DW_TAG' | wc -l
130
$ readelf -w b.out | grep '(DW_TAG' | wc -l
130
$ readelf -w c.out | grep '(DW_TAG' | wc -l
5356
$ readelf -w d.out | grep '(DW_TAG' | wc -l
5356
...

Now consider a gdb script that traces the dwz invocations:
...
$ cat gdb.script
b dwz
commands
continue
end
run
...

We run in multifile mode, with a low-mem limit of 1000 dies, and trace into
LOG:
...
$ gdb \
    -batch \
    -x gdb.script \
    --args dwz -m3 -l1000 a.out b.out c.out d.out \
    > LOG 2>&1
...

which we then summarize as follows:
...
$ grep 'dwz (' LOG | awk '{print $5}'
"a.out",
"b.out",
"c.out",
"c.out",
"d.out",
"d.out",
"a.out",
"b.out",
"c.out",
"d.out",
...

The first 6 invocations are according to plan:
- a.out and b.out have fewer DIEs than 1000, and are processed.
- c.out and d.out have more DIEs than 1000, and are each processed twice:
  - once in regular mode (where dwz stops at a 1000 processed DIEs and returns
    2), and 
  - once in low-mem mode.

However, then all 4 files are once more processed in fi_multifile mode, while
the intention is that c.out and d.out (being bigger than the low-mem limit) are
not processed anymore.

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[Bug default/24274] low-mem files processed in multifile mode

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=24274

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at redhat dot com

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
AFAIU, there is code intended to prevent this scenario from happening at the
end of dwz:
...
  free (dso);
  if (ret == 0 && !low_mem)
    res->res = 0;
  return ret;
...

But the low_mem condition is never true here, because cleanup is run before
arriving there, which sets multifile_mode to 0.

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[Bug default/24274] low-mem files processed in multifile mode

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=24274

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
posted patch: https://sourceware.org/ml/dwz/2019-q1/msg00058.html

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[Bug default/24274] low-mem files processed in multifile mode

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=24274

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
Reclassifying as enhancement.

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[Bug default/24274] low-mem files processed in multifile mode

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=24274

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at klomp dot org

--- Comment #4 from Mark Wielaard <mark at klomp dot org> ---
Has an unreviewed patch, see Comment #2

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