Hi!

On 2023-06-15T17:15:54+0200, I wrote:
> On 2023-06-06T20:31:21+0100, Jonathan Wakely <jwakely@redhat.com> wrote:
>> On Tue, 6 Jun 2023 at 20:14, Thomas Schwinge <thomas@codesourcery.com> wrote:
>>> This issue comes up in context of me working on C++ support for GCN and
>>> nvptx target.  Those targets shall default to '-fno-exceptions' -- or,
>>> "in other words", '-fexceptions' is not supported.  (Details omitted
>>> here.)
>>>
>>> It did seem clear to me that with such a configuration it'll be hard to
>>> get clean test results.  Then I found code in
>>> 'gcc/testsuite/lib/gcc-dg.exp:gcc-dg-prune':
>>>
>>>     # If exceptions are disabled, mark tests expecting exceptions to be enabled
>>>     # as unsupported.
>>>     if { ![check_effective_target_exceptions_enabled] } {
>>>         if [regexp "(^|\n)\[^\n\]*: error: exception handling disabled" $text] {
>>>             return "::unsupported::exception handling disabled"
>>>         }
>>>
>>> ..., which, in a way, sounds as if the test suite generally is meant to
>>> produce useful results for '-fno-exceptions', nice surprise!
>>>
>>> Running x86_64-pc-linux-gnu (not yet GCN, nvptx) 'make check' with:
>>>
>>>     RUNTESTFLAGS='--target_board=unix/-fno-exceptions\{,-m32\}'
>>>
>>> ..., I find that indeed this does work for a lot of test cases, where we
>>> then get (random example):
>>>
>>>      PASS: g++.dg/coroutines/pr99710.C  (test for errors, line 23)
>>>     -PASS: g++.dg/coroutines/pr99710.C (test for excess errors)
>>>     +UNSUPPORTED: g++.dg/coroutines/pr99710.C: exception handling disabled
>>>
>>> ..., due to:
>>>
>>>      [...]/g++.dg/coroutines/pr99710.C: In function 'task my_coro()':
>>>     +[...]/g++.dg/coroutines/pr99710.C:18:10: error: exception handling
>>> disabled, use '-fexceptions' to enable
>>>      [...]/g++.dg/coroutines/pr99710.C:23:7: error: await expressions are
>>> not permitted in handlers
>>>      compiler exited with status 1
>>>
>>> But, we're nowhere near clean test results: PASS -> FAIL as well as
>>> XFAIL -> XPASS regressions, due to 'error: exception handling disabled'
>>> precluding other diagnostics seems to be one major issue.
>>>
>>> Is there interest in me producing the obvious (?) changes to those test
>>> cases, such that compiler g++ as well as target library libstdc++ test
>>> results are reasonably clean?  (If you think that's all "wasted effort",
>>> then I suppose I'll just locally ignore any FAILs/XPASSes/UNRESOLVEDs
>>> that appear in combination with
>>> 'UNSUPPORTED: [...]: exception handling disabled'.)
>>
>> I would welcome that for libstdc++. [...]

> Not having heard anything contrary regarding the compiler side of things,
> I've now been working on that, see below.

>>> Otherwise, a number of test cases need DejaGnu directives
>>> conditionalized on 'target exceptions_enabled'.
>
> Before I get to such things, even simpler: OK to push the attached
> "Skip a number of C++ test cases for '-fno-exceptions' testing"?

Similarly, OK to push the attached
"Skip a number of C++ 'g++.dg/tree-prof/' test cases for '-fno-exceptions' testing"?


Grüße
 Thomas


>>> (Or,
>>> 'error: exception handling disabled' made a "really late" diagnostic, so
>>> that it doesn't preclude other diagnostics?  I'll have a look.  Well,
>>> maybe something like: in fact do not default to '-fno-exceptions', but
>>> instead emit 'error: exception handling disabled' only if in a "really
>>> late" pass we run into exceptions-related constructs that we cannot
>>> support.  That'd also avoid PASS -> UNSUPPORTED "regressions" when
>>> exception handling in fact gets optimized away, for example.  I like that
>>> idea, conceptually -- but is it feasible to implement..?)
>>
>> IMHO just [...] using [an effective target keyword] in test
>> selectors seems simpler, and doesn't require changes to the compiler, just
>> the tests.
>
> I still like the idea, but yes, I've mentally put it on file "for later"
> (ha, ha, ha...) -- it doesn't seem obvious to implement.
>
>
> Grüße
>  Thomas


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