Tidy checks for sufficient suppression properties.

Each suppression specification must have at least one of a documented
per-suppression type list of properties defined if it is to be
considered at all.

At present:

- suppression specifications which fail the check are silently ignored
- in the function suppression case, the check does not trigger an
  early return and risks a later null pointer dereference.

This commit:

- reimplements the checks using arrays and helper function calls
- adds a helper function to determine if a suppression specification
  is going to be ignored due a lack of properties
- makes the parsing functions return failure early if the check fails

Inconsistencies between suppression types (in particular, the
treatment of the "label" property) remain.

The only behavioural change may be to how present but empty properties
are handled. This is an edge case that may be worth revisiting in a
more general fashion in a later commit.

	* src/abg-suppression.cc (check_sufficient_props): New helper
	function to check for sufficient properties in a section.
	(read_type_suppression): Replace conditional logic with call
	to check_sufficient_props.
	(read_function_suppression): Ditto.
	(read_variable_suppression): Ditto.
	(read_file_suppression): Ditto.
	* tests/data/test-diff-suppr/test15-suppr-added-fn-4.suppr:
	Explain why the suppression will be ignored.
	* tests/data/test-diff-suppr/test16-suppr-removed-fn-4.suppr:
	Ditto.
	* tests/data/test-diff-suppr/test17-suppr-added-var-4.suppr:
	Ditto.
	* tests/data/test-diff-suppr/test18-suppr-removed-var-4.suppr:
	Ditto.

Signed-off-by: Giuliano Procida <gprocida@google.com>
5 files changed