<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<p><br>
</p>
<div class="moz-cite-prefix">On 1/7/19 4:43 PM, Richard Smith wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAOfiQqneq9A_6VAHS0bVZprEXs3Vzeb5P6wGdk0PtnKOoAdAew@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">On Mon, 7 Jan 2019 at 16:12, Erik
Pilkington via cfe-commits <<a
href="mailto:cfe-commits@lists.llvm.org"
moz-do-not-send="true">cfe-commits@lists.llvm.org</a>>
wrote:<br>
</div>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
<p>On 1/7/19 3:51 PM, Richard Smith wrote:<br>
</p>
<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">On Mon, 7 Jan 2019 at 13:57, Erik
Pilkington via cfe-commits <<a
href="mailto:cfe-commits@lists.llvm.org"
target="_blank" moz-do-not-send="true">cfe-commits@lists.llvm.org</a>>
wrote:<br>
</div>
<div class="gmail_quote">
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Author:
epilk<br>
Date: Mon Jan 7 13:54:00 2019<br>
New Revision: 350572<br>
<br>
URL: <a
href="http://llvm.org/viewvc/llvm-project?rev=350572&view=rev"
rel="noreferrer" target="_blank"
moz-do-not-send="true">http://llvm.org/viewvc/llvm-project?rev=350572&view=rev</a><br>
Log:<br>
Add a __has_feature check for namespaces on
#pragma clang attribute.<br>
</blockquote>
<div><br>
</div>
<div>Should this be __has_extension rather
than __has_feature, since it's not a
standard feature?</div>
</div>
</div>
</blockquote>
<p><br>
</p>
<p>I suppose, but it doesn't really seem like that's
the rule that we're following here. If you look at
every other FEATURE(...) above this, they all have
to do with clang extensions like attributes and
sanitizers, which obviously aren't standard
features. Every EXTENSION(...) has to do with
language features that are shared between
languages (cxx_fixed_enum in C, for instance). So
it seems like the most internally consistent place
to put this is in FEATURE(...). WDYT?</p>
</div>
</blockquote>
<div>What you're seeing is a historical legacy of the
time before the current approach. The design and
documented intent of __has_feature is that it checks
for standardized features. See the documentation here,
and particularly the note about backwards
compatibility:</div>
<div><br>
</div>
<div><a
href="https://clang.llvm.org/docs/LanguageExtensions.html#has-feature-and-has-extension"
moz-do-not-send="true">https://clang.llvm.org/docs/LanguageExtensions.html#has-feature-and-has-extension</a><br>
</div>
<div><br>
</div>
<div>... and the design discussion when __has_extension
was introduced:</div>
<div>
<div><br class="gmail-Apple-interchange-newline">
<a
href="http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20110425/041452.html"
moz-do-not-send="true">http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20110425/041452.html</a><br>
</div>
<br class="gmail-Apple-interchange-newline">
</div>
<div>... and the comment on HasFeature in
Lex/PPMacroExpansion.cpp:<br>
</div>
<div><br>
</div>
<div>
<div>/// HasFeature - Return true if we recognize and
implement the feature</div>
<div>/// specified by the identifier as a standard
language feature.</div>
</div>
<div><br>
</div>
<div>We seem to have detached that comment from the
actual list of features when the features were moved
to a .def file. Oops :(</div>
<div><br>
</div>
<div>If we want to revisit the design based on
experience using __has_feature / __has_extension, I'm
all for that (the distinction between the two seems
confusing and not especially useful to me; the
behavior of the current language mode can be tested
using eg __STDC_VERSION__ and __cplusplus, so the only
thing that's really interesting for us to expose is
what features the current compliation supports), but
we should follow the current design until we do.<br>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
<p><br>
</p>
<p>Yeah, it doesn't really seem like a useful distinction. Anyways,
I added a comment to this file and fixed this in r350642. Thanks!<br>
</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:CAOfiQqneq9A_6VAHS0bVZprEXs3Vzeb5P6wGdk0PtnKOoAdAew@mail.gmail.com">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_quote">
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Support
for this was added in r349845.<br>
<br>
Modified:<br>
cfe/trunk/docs/LanguageExtensions.rst<br>
cfe/trunk/include/clang/Basic/Features.def<br>
cfe/trunk/test/Sema/pragma-attribute-namespace.c<br>
<br>
Modified:
cfe/trunk/docs/LanguageExtensions.rst<br>
URL: <a
href="http://llvm.org/viewvc/llvm-project/cfe/trunk/docs/LanguageExtensions.rst?rev=350572&r1=350571&r2=350572&view=diff"
rel="noreferrer" target="_blank"
moz-do-not-send="true">http://llvm.org/viewvc/llvm-project/cfe/trunk/docs/LanguageExtensions.rst?rev=350572&r1=350571&r2=350572&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/docs/LanguageExtensions.rst
(original)<br>
+++ cfe/trunk/docs/LanguageExtensions.rst
Mon Jan 7 13:54:00 2019<br>
@@ -2725,7 +2725,9 @@ same namespace. For
instance:<br>
Without the namespaces on the macros,
``other_function`` will be annotated with<br>
``[[noreturn]]`` instead of
``__attribute__((unavailable))``. This may
seem like<br>
a contrived example, but its very possible
for this kind of situation to appear<br>
-in real code if the pragmas are spread out
across a large file.<br>
+in real code if the pragmas are spread out
across a large file. You can test if<br>
+your version of clang supports namespaces
on ``#pragma clang attribute`` with<br>
+``__has_feature(pragma_clang_attribute_namespaces)``.<br>
<br>
Subject Match Rules<br>
-------------------<br>
<br>
Modified:
cfe/trunk/include/clang/Basic/Features.def<br>
URL: <a
href="http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Features.def?rev=350572&r1=350571&r2=350572&view=diff"
rel="noreferrer" target="_blank"
moz-do-not-send="true">http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Features.def?rev=350572&r1=350571&r2=350572&view=diff</a><br>
==============================================================================<br>
---
cfe/trunk/include/clang/Basic/Features.def
(original)<br>
+++
cfe/trunk/include/clang/Basic/Features.def
Mon Jan 7 13:54:00 2019<br>
@@ -69,6 +69,7 @@
FEATURE(attribute_overloadable, true)<br>
FEATURE(attribute_unavailable_with_message,
true)<br>
FEATURE(attribute_unused_on_fields, true)<br>
FEATURE(attribute_diagnose_if_objc, true)<br>
+FEATURE(pragma_clang_attribute_namespaces,
true)<br>
FEATURE(blocks, LangOpts.Blocks)<br>
FEATURE(c_thread_safety_attributes, true)<br>
FEATURE(cxx_exceptions,
LangOpts.CXXExceptions)<br>
<br>
Modified:
cfe/trunk/test/Sema/pragma-attribute-namespace.c<br>
URL: <a
href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/pragma-attribute-namespace.c?rev=350572&r1=350571&r2=350572&view=diff"
rel="noreferrer" target="_blank"
moz-do-not-send="true">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/pragma-attribute-namespace.c?rev=350572&r1=350571&r2=350572&view=diff</a><br>
==============================================================================<br>
---
cfe/trunk/test/Sema/pragma-attribute-namespace.c
(original)<br>
+++
cfe/trunk/test/Sema/pragma-attribute-namespace.c
Mon Jan 7 13:54:00 2019<br>
@@ -1,5 +1,9 @@<br>
// RUN: %clang_cc1 -fsyntax-only -verify %s<br>
<br>
+#if
!__has_feature(pragma_clang_attribute_namespaces)<br>
+#error<br>
+#endif<br>
+<br>
#pragma clang attribute MyNamespace.push
(__attribute__((annotate)),
apply_to=function) // expected-error 2
{{'annotate' attribute}}<br>
<br>
int some_func(); // expected-note{{when
applied to this declaration}}<br>
<br>
<br>
_______________________________________________<br>
cfe-commits mailing list<br>
<a href="mailto:cfe-commits@lists.llvm.org"
target="_blank" moz-do-not-send="true">cfe-commits@lists.llvm.org</a><br>
<a
href="http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits"
rel="noreferrer" target="_blank"
moz-do-not-send="true">http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits</a><br>
</blockquote>
</div>
</div>
</blockquote>
</div>
_______________________________________________<br>
cfe-commits mailing list<br>
<a href="mailto:cfe-commits@lists.llvm.org"
target="_blank" moz-do-not-send="true">cfe-commits@lists.llvm.org</a><br>
<a
href="http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits"
rel="noreferrer" target="_blank"
moz-do-not-send="true">http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits</a><br>
</blockquote>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</body>
</html>