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

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?

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.

Joseph S. Myers

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