[Bug exp/34051] [gdb/exp] Incorrect namespace prefix ignored

https://sourceware.org/bugzilla/show_bug.cgi?id=34051

--- Comment #5 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom de Vries <[email protected]>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=6f6e739987d6f0b904aa8e6d6bc7cc4e3d71d408

commit 6f6e739987d6f0b904aa8e6d6bc7cc4e3d71d408
Author: Tom de Vries <[email protected]>
Date:   Tue Jul 14 10:43:14 2026 +0200

    [gdb/exp] Fix ignoring of incorrect namespace prefix

    Consider test.c, compiled to a.out using "g++ -g test.c":
    ...
         1  namespace mod_a { int xxx = 10; }
         2  namespace mod_b { using namespace mod_a;
         3                    int yyy = 20; }
         4  int main (void) {
         5    using namespace mod_b;
         6    void (xxx + yyy);
         7    return 0;
         8  }
    ...

    When trying to print the value of non-existent variable mod_a::yyy, we get:
    ...
    $ gdb -q -batch a.out -ex start -ex "print mod_a::yyy"
      ...
    Temporary breakpoint 1, main () at test.c:7
    7         return 0;
    $1 = 20
    ...

    The problem is in cp_lookup_symbol_via_imports, where we decide that the
    "using namespace mod_b" from main is applicable in scope mod_a.

    More concretely, cp_lookup_symbol_via_imports is called with:
    - scope == "mod_a",
    - name == "yyy", and
    - block.m_function.m_name == "main()",
    and when looking at "using namespace mod_b":
    ...
    (gdb) p *current
    $12 = {import_src = 0x344018c "mod_b", import_dest = 0x1b477a0 "",
           alias = 0x0, declaration = 0x0, next = 0x0, decl_line = 5,
           searched = 0, excludes = {0x0}}
    ...
    we hit "directive_match = true" because strlen (current->import_dest) == 0.

    Fix this by being more strict in the calculation of directive_match:
    ...
              if (len == 0)
    -           directive_match = true;
    +           {
    +             const char *current_scope = (block->function_block () !=
nullptr
    +                                          ? block->scope ()
    +                                          : nullptr /* Don't know.  */);
    +             directive_match = (current_scope != nullptr
    +                                ? streq (scope, current_scope)
    +                                : true /* Assume there's a match.  */);
    +           }
    ...
    which gets us:
    - current_scope == "", and
    - directive_match == false,
    because scope == "mod_a", so streq (scope, current_scope) == false.

    As is clear from the code, in case we don't know the current scope, we
assume
    there's a match.  This may be harmless, or this may describe a cornercase
we
    haven't run into yet.  If so, it's a pre-existing issue.

    The new test-case contains regression tests for:
    - PR34051, and
    - PR34034 for which it contains a kfail.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34051

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