Re: [PATCH v2][C][ADA] use function descriptors instead of trampolines in C

["Uecker, Martin" <Martin dot Uecker at med dot uni-goettingen dot de>]

Am Dienstag, den 21.08.2018, 21:34 +0000 schrieb Joseph Myers:
> On Tue, 21 Aug 2018, Uecker, Martin wrote:
> 
> > > I don't see why this is target-specific (if it is, the documentation for 
> > > users in invoke.texi should explain what targets it works for and what it 
> > > doesn't work for) anyway.  I'd expect it to be a target-independent 
> > > feature with a target-independent test or tests.
> > 
> > My understanding is that this is a target-independent feature which
> > has not yet been implemented for all targets. The existing
> > documentation does not reflect this.
> 
> How does one tell which targets do or do not support it?

There is a target hook

TARGET_CUSTOM_FUNCTION_DESCRIPTORS

But I am not sure how to get this information to the testsuite.

> For tests for features supported on some but not all targets, we use 
> effective-target keywords.  Of course you need to be careful about how you 
> implement those keywords: you don't want the implementation of the keyword 
> to be essentially the same as the test being conditioned, to avoid a bug 
> in the implementation quietly causing the test to be disabled.  But the 
> implementation of the keyword might e.g. have a blacklist of targets that 
> do not yet support the feature, with the expectation that the test should 
> run and pass on all other targets.

gcc/testsuite/lib/target-supports.exp

there seems to be infrastructure to implement this. The information seems
to come from a "target_info" structure (?) but I do not see where this
is populated.

Best,
Martin