Hello, At the last GNU Cauldron, Richard Biener and I talked about DWARF output testing. Except for guality tests, which are disabled on several targets, the only way tests check the DWARF is scanning the annotated assembly (-dA), making it hard to write reliable tests.
For instance, checking the number of times DW_AT_location is present in order to check that some specific variable is assigned one is fuzzy. Depending on the target and on the evolution of the compiler, the number of output variables, or which one is assigned a location can vary legitimately but still make the test fail. On my side, I already had written an out-of-tree testsuite for the DWARF features I added for Ada. This testsuite uses a DWARF parser in order to perform checks on a tree: <https://github.com/pmderodat/dwarf-ada-testsuite/>. I had to update it a couple of times, for instance when a change created a DW_TAG_const_type DIE or removed one somewhere in a type tree, but that’s very rare. I would say that I’m satisfied with the checks I could express, but I don’t remember I ever caught a regression with them, so I have no representative experience to share in this area. Maybe DWARF back-end developpers do a too good job. ;-) Anyway, Richard and I discussed about doing something similar in-tree, and here is a candidate set of patches to achieve that: * The first patch installs DejaGNU scripts to run a Python interpreter in testcases. * The second one installs other DejaGNU scripts to detect DWARF dumping tools, plus a small Python library to parse and pattern match DIEs and their attributes. It also adds several C and Ada tests as examples; these are inspired by existing homonym tests based on assembly scanning. For now, this supports only platforms where objdump is available for the current target, but extending it to other tools, such as otool on Darwin should be doable. I would appreciate feedback about the idea and the implementation I propose. This is the first time I do more in the testsuite than just adding new tests, so thank you in advance for you patience in reviewing these. :-) I tested these patches on x86_64-linux.
