[Bug libdw/27405] New: libdw_get_srcfiles should not imply srclines

[Bug libdw/27405] New: libdw_get_srcfiles should not imply srclines

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27405

            Bug ID: 27405
           Summary: libdw_get_srcfiles should not imply srclines
           Product: elfutils
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libdw
          Assignee: unassigned at sourceware dot org
          Reporter: fche at redhat dot com
                CC: elfutils-devel at sourceware dot org
  Target Milestone: ---

In debuginfod, we use _get_srcfiles to fetch file names only.  We do not care
about srclines, so libdw's effort in allocating all that memory, and filling it
in, is just a waste.  Let's make srcfiles great by skipping the per-line data.

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[Bug libdw/27405] libdw_get_srcfiles should not imply srclines

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27405

Mark Wielaard <mark at klomp dot org> changed:

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

--- Comment #1 from Mark Wielaard <mark at klomp dot org> ---
Note that the issue is here in libdw/dwarf_getsrcfiles.c:

          /* Let the more generic function do the work.  It'll create more
             data but that will be needed in an real program anyway.  */
          res = INTUSE(dwarf_getsrclines) (cudie, &lines, &nlines);

debuginfod shows that comment is wrong.

There is also the internal __libdw_getsrclines function which is used in a
couple of place to "only" get the srcfiles.

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[Bug libdw/27405] libdw_get_srcfiles should not imply srclines

[amerey at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27405

Aaron Merey <amerey at redhat dot com> changed:

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

--- Comment #2 from Aaron Merey <amerey at redhat dot com> ---
Proposed patch:
https://sourceware.org/pipermail/elfutils-devel/2024q1/006973.html

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[Bug libdw/27405] libdw_get_srcfiles should not imply srclines

[amerey at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27405

Aaron Merey <amerey at redhat dot com> changed:

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

--- Comment #3 from Aaron Merey <amerey at redhat dot com> ---
Fixed in the following commit:

commit d4b0848be5f575ff9464fee12ce7be416e4fb392
Author: Aaron Merey <amerey@redhat.com>
Date:   Mon Mar 25 15:57:25 2024 -0400

    libdw: dwarf_getsrcfiles should not imply dwarf_getsrclines

    dwarf_getsrcfiles causes line data to be read in addition to file data.
    This is wasteful for programs which only need file or directory names.
    Debuginfod server is one such example.

    Fix this by moving the srcfile reading in read_srclines into a separate
    function read_srcfiles.  This change improves debuginfod server's max
    resident set size by up to 75% during rpm indexing.

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