[clang] [Clang] Allow the use of [[gnu::visibility]] with #pragma clang attribute (PR #145653)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Nikolas Klauser (philnik777)

<details>
<summary>Changes</summary>

I don't see any reason this shouldn't be allowed. AFAICT this is only disabled due to the heuristics used to determine whether it makes sense to allow the use of an attribute with `#pragma clang attribute`.

This allows libc++ to drop `_LIBCPP_HIDE_FROM_ABI` in a lot of places, making the library significantly easier to read.



---
Full diff: https://github.com/llvm/llvm-project/pull/145653.diff


3 Files Affected:

- (modified) clang/include/clang/Basic/Attr.td (+1) 
- (modified) clang/test/CodeGen/visibility.c (+10) 
- (modified) clang/test/Sema/attr-visibility.c (+6) 


``````````diff
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index f113cd2ba2fbf..7272715558bf2 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -3735,6 +3735,7 @@ def Visibility : InheritableAttr {
                            ["default", "hidden", "internal", "protected"],
                            ["Default", "Hidden", "Hidden", "Protected"]>];
   let MeaningfulToClassTemplateDefinition = 1;
+  let PragmaAttributeSupport = 1;
   let Documentation = [Undocumented];
 }
 
diff --git a/clang/test/CodeGen/visibility.c b/clang/test/CodeGen/visibility.c
index ee760ec77879e..3abd70870bf92 100644
--- a/clang/test/CodeGen/visibility.c
+++ b/clang/test/CodeGen/visibility.c
@@ -72,3 +72,13 @@ __private_extern__ int test4 = 10;
 // CHECK-HIDDEN-LABEL: define hidden void @test5()
 __attribute__((availability(macosx,introduced=10.5,deprecated=10.6)))
 __private_extern__ void test5(void) {}
+
+
+#pragma clang attribute push([[gnu::visibility("hidden")]], apply_to=function)
+
+// CHECK-DEFAULT-LABEL: define hidden void @func()
+// CHECK-PROTECTED-LABEL: define hidden void @func()
+// CHECK-HIDDEN-LABEL: define hidden void @func()
+void func(void) {}
+
+#pragma clang attribute pop
diff --git a/clang/test/Sema/attr-visibility.c b/clang/test/Sema/attr-visibility.c
index 4acca7a7f69a3..0497e9760c44f 100644
--- a/clang/test/Sema/attr-visibility.c
+++ b/clang/test/Sema/attr-visibility.c
@@ -25,3 +25,9 @@ typedef int __attribute__((visibility("default"))) bar; // expected-warning {{'v
 int x __attribute__((type_visibility("default"))); // expected-error {{'type_visibility' attribute only applies to types and namespaces}}
 
 int PR17105 __attribute__((visibility(hidden))); // expected-error {{'visibility' attribute requires a string}}
+
+#pragma clang attribute push([[gnu::visibility("default")]], apply_to=function)
+
+void func(void) {}
+
+#pragma clang attribute pop

``````````

</details>


https://github.com/llvm/llvm-project/pull/145653