[Bug symtab/31622] New: [gdb/symtab] find_epilogue_using_linetable fails to find entry in function with two linetables

[Bug symtab/31622] New: [gdb/symtab] find_epilogue_using_linetable fails to find entry in function with two linetables

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31622

            Bug ID: 31622
           Summary: [gdb/symtab] find_epilogue_using_linetable fails to
                    find entry in function with two linetables
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: symtab
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

Bernd Edlinger reported the following problem and fix in
find_epilogue_using_linetable (
https://sourceware.org/pipermail/gdb-patches/2024-April/207928.html ).

This came up in a discussion for a patch for PR31268, but it's an independent
issue.

Consider the following test-case:
...
$ cat hello.c 
#include <stdio.h>
int main()
{
  printf("hello ");
  #include "world.inc"
/*** End of hello.c ***/

$ cat world.inc 
  printf("world\n");
  return 0;
}
/*** End of world.inc ***/

$ gcc -g -o hello hello.c
...

The corresponding disassembly for main is:
...
0000000000400557 <main>:
  400557:       55                      push   %rbp
  400558:       48 89 e5                mov    %rsp,%rbp
  40055b:       bf 24 06 40 00          mov    $0x400624,%edi
  400560:       b8 00 00 00 00          mov    $0x0,%eax
  400565:       e8 f6 fe ff ff          call   400460 <printf@plt>
  40056a:       bf 2b 06 40 00          mov    $0x40062b,%edi
  40056f:       e8 dc fe ff ff          call   400450 <puts@plt>
  400574:       b8 00 00 00 00          mov    $0x0,%eax
  400579:       5d                      pop    %rbp
  40057a:       c3                      ret
...

And the corresponding line table is:
...
hello.c:
File name                Line number    Starting address    View    Stmt
hello.c                            3            0x400557               x
hello.c                            4            0x40055b               x

./world.inc:[++]
world.inc                          1            0x40056a               x
world.inc                          2            0x400574               x
world.inc                          3            0x400579               x
world.inc                          -            0x40057b
...

Now, say we have an epilogue_begin marker at 0x400579 in world.inc.

We won't find it using find_epilogue_using_linetable, because it does:
...
  const struct symtab_and_line sal = find_pc_line (start_pc, 0);
...
which gets us the line table for hello.c.

Proposed patch:
...
-  const struct symtab_and_line sal = find_pc_line (start_pc, 0);
+  const struct symtab_and_line sal = find_pc_line (end_pc - 1, 0);
...
which gets us the linetable for world.inc instead.

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[Bug symtab/31622] [gdb/symtab] find_epilogue_using_linetable fails to find entry in function with two linetables

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31622

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bernd.edlinger at hotmail dot de

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[Bug symtab/31622] [gdb/symtab] find_epilogue_using_linetable fails to find entry in function with two linetables

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31622

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
https://sourceware.org/pipermail/gdb-patches/2024-April/207960.html

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[Bug symtab/31622] [gdb/symtab] find_epilogue_using_linetable fails to find entry in function with two linetables

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31622

--- Comment #2 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Bernd Edlinger <edlinger@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=730f5068f5fb6613e4faa2efc2309cd107562cbd

commit 730f5068f5fb6613e4faa2efc2309cd107562cbd
Author: Bernd Edlinger <bernd.edlinger@hotmail.de>
Date:   Tue Apr 9 09:27:53 2024 +0000

    Handle two-linetable function in find_epilogue_using_linetable

    Consider the following test-case:
    ...
    $ cat hello.c
    int main()
    {
      printf("hello ");
      #include "world.inc"
    $ cat world.inc
      printf("world\n");
      return 0;
    }
    $ gcc -g hello.c
    ...

    The line table for the compilation unit, consisting just of
    function main, is translated into these two gdb line tables, one for
hello.c
    and one for world.inc:
    ...
    compunit_symtab: hello.c
    symtab: hello.c
    INDEX  LINE   REL-ADDRESS UNREL-ADDRESS IS-STMT PROLOGUE-END EPILOGUE-BEGIN
    0      3      0x400557    0x400557      Y
    1      4      0x40055b    0x40055b      Y
    2      END    0x40056a    0x40056a      Y

    compunit_symtab: hello.c
    symtab: world.inc
    INDEX  LINE   REL-ADDRESS UNREL-ADDRESS IS-STMT PROLOGUE-END EPILOGUE-BEGIN
    0      1      0x40056a    0x40056a      Y
    1      2      0x400574    0x400574      Y
    2      3      0x400579    0x400579      Y
    3      END    0x40057b    0x40057b      Y
    ...

    The epilogue of main starts at 0x400579:
    ...
      400579:       5d                      pop    %rbp
      40057a:       c3                      ret
    ...

    Now, say we have an epilogue_begin marker in the line table at 0x400579.

    We won't find it using find_epilogue_using_linetable, because it does:
    ...
      const struct symtab_and_line sal = find_pc_line (start_pc, 0);
    ...
    which gets us the line table for hello.c.

    Fix this by using "find_pc_line (end_pc - 1, 0)" instead.

    Tested on x86_64-linux.

    Co-Authored-By: Tom de Vries <tdevries@suse.de>

    PR symtab/31622
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31622

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[Bug symtab/31622] [gdb/symtab] find_epilogue_using_linetable fails to find entry in function with two linetables

[bernd.edlinger at hotmail dot de]

https://sourceware.org/bugzilla/show_bug.cgi?id=31622

--- Comment #3 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
fixed on master

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[Bug symtab/31622] [gdb/symtab] find_epilogue_using_linetable fails to find entry in function with two linetables

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31622

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |15.1

--- Comment #4 from Tom de Vries <vries at gcc dot gnu.org> ---
Fixed.

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