Handle explicit template specializations in sg.pl

[Ozaq]

Description

sg.pl crashes when a header contains an explicit template specialization (template <>) because template_args() expects class/bool/int after '<' but gets '>'.

Return an empty parameter list from template_args() on 'template <>' and skip the entire specialization in parse_template(), since explicit specializations are not new class definitions and should not generate .b files.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[Copilot]

Pull request overview

Prevents sg.pl from crashing on explicit template specializations (template <>) by detecting the empty parameter list case and skipping parsing of the specialization body.

Changes:

• Return an empty parameter list from template_args() when encountering template <>.
• In parse_template(), detect explicit specializations and skip the entire declaration/body so they don’t generate .b outputs.

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[wdeconinck]

Hi @Ozaq could you please provide a test that was previously crashing?

[marcosbento]

If I understood correctly, the issue occurs when the file contains something like:

// Forwarded classes
template <> class TheNuisance< std::string >;

class X {};

which ends with the failure > is not (class|bool|int) at cmake/sg.pl line 45. upon finding the <> of TheNuisance, where normally the whole construct would be ignored as it is just a class forward declaration.

Assuming this is indeed the problem the issue is fixed! But this certainly deserves a test to ensure the use case is handled properly

[marcosbento]

Please add a test to cover the failure test that triggered these changes.

[wdeconinck]

Test requested.

[Ozaq]

@wdeconinck / @marcosbento Tests added

[wdeconinck]

All runners are failing

        Start 40: test_sg_pl
  Process not started
   /opt/actions-runner/work/_work/ecbuild/ecbuild/build/tests/sg_pl/run-test.sh
  [permission denied]
  33/40 Test #40: test_sg_pl .........................................***Not Run   0.00 sec

[marcosbento]

@wdeconinck I've fixed a few outstanding issues, and the ecbuild build (including the new test) is passing -- the issues detected downstream don't seem related.

[wdeconinck]

Great Thanks All!