[Bug symtab/30738] New: [gdb/symtab, readnow] different symtab order gives different results

[Bug symtab/30738] New: [gdb/symtab, readnow] different symtab order gives different results

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30738

            Bug ID: 30738
           Summary: [gdb/symtab, readnow] different symtab order gives
                    different results
           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: ---

[ Previously noted at PR25857 ]

Consider the following test-case:
...
$ cat main.c
int
main ()
{
  return 0;
}
$ cat test.c
static int aaa = 1;
$ cat test2.c
static int aaa = 2;
...

Compiled like this:
...
$ gcc main.c test.c test2.c -g
...

Results with -readnow are different:
...
$ gdb -q -batch a.out -ex "print aaa"
$1 = 1
$ gdb -q -batch -readnow a.out -ex "print aaa"
$1 = 2
...

Readnow expands the symtabs in the (reverse?) order of the debug info, while
selective expansion of symtabs results in a list with expansion order.

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[Bug symtab/30738] [gdb/symtab, readnow] different symtab order gives different results

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30738

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=25857

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[Bug symtab/30738] [gdb/symtab, readnow] different symtab order gives different results

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30738

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
FWIW the order of results here was never really guaranteed.
Cases like this can be resolved with syntax like
(gdb) print 'test2.c'::aaa

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[Bug symtab/30738] [gdb/symtab, readnow] different symtab order gives different results

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30738

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
Created attachment 15054
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15054&action=edit
Experiment patch

I wrote this patch as an experiment: rather than storing in reverse expansion
order, store in expansion order.

This identified part objfile::map_symtabs_matching_filename as a place (the
only one?) where we use compunit_symtabs as a means to retrieve recently
expanded symtabs.

There where fails in only two test-cases (gdb.mi/mi-sym-info.exp and
gdb.python/py-symbol.exp), and those look like the test-cases just needs
updating.

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