commit 79f87be6888d13a94661be9d8908c83dd2229c9b
author Sergei Barannikov <barannikov88@gmail.com> Sat Sep 02 05:22:25 2023 +0300
committer Sergei Barannikov <barannikov88@gmail.com> Tue Oct 10 09:03:55 2023 +0300
tree c60794cc0bb41e4786c21edc17410cfea819ec8f
parent 792674400f6f04a074a3827349ed0e2ac10067f6

[clang] Fix several issues in the generated AttrHasAttributeImpl.inc

1. The generated file contained a lot of duplicate switch cases, e.g.:
```
switch (Syntax) {
case AttributeCommonInfo::Syntax::AS_GNU:
  return llvm::StringSwitch<int>(Name)
...
    .Case("error", 1)
    .Case("warning", 1)
    .Case("error", 1)
    .Case("warning", 1)
```

2. Some attributes were listed in wrong places, e.g.:
```
case AttributeCommonInfo::Syntax::AS_CXX11: {
if (ScopeName == "") {
  return llvm::StringSwitch<int>(Name)
...
    .Case("warn_unused_result", LangOpts.CPlusPlus11 ? 201907 : 0)
```

`warn_unused_result` is a non-standard attribute and should not be
available as [[warn_unused_result]].

3. Some attributes had the wrong version, e.g.:
```
case AttributeCommonInfo::Syntax::AS_CXX11: {
} else if (ScopeName == "gnu") {
  return llvm::StringSwitch<int>(Name)
...
    .Case("fallthrough", LangOpts.CPlusPlus11 ? 201603 : 0)
```

[[gnu::fallthrough]] is a non-standard spelling and should not have the
standard version. Instead, __has_cpp_attribute should return 1 for it.

There is another issue with attributes that share spellings, e.g.:
```
    .Case("interrupt", true && (T.getArch() == llvm::Triple::arm || ...) ? 1 : 0)
    .Case("interrupt", true && (T.getArch() == llvm::Triple::avr) ? 1 : 0)
...
    .Case("interrupt", true && (T.getArch() == llvm::Triple::riscv32 || ...) ? 1 : 0)
```
As can be seen, __has_attribute(interrupt) would only return true for
ARM targets. This patch does not address this issue.

Differential Revision: https://reviews.llvm.org/D159393

clang/test/Preprocessor/has_c_attribute.c

diff --git a/clang/test/Preprocessor/has_c_attribute.c b/clang/test/Preprocessor/has_c_attribute.c
index 2f4fdf1..3332571 100644
--- a/clang/test/Preprocessor/has_c_attribute.c
+++ b/clang/test/Preprocessor/has_c_attribute.c
@@ -9,6 +9,15 @@
 // CHECK: __nodiscard__: 202003L
 C2x(__nodiscard__)
 
+// CHECK: warn_unused_result: 0
+C2x(warn_unused_result)
+
+// CHECK: gnu::warn_unused_result: 1
+C2x(gnu::warn_unused_result)
+
+// CHECK: clang::warn_unused_result: 0
+C2x(clang::warn_unused_result)
+
 // CHECK: selectany: 0
 C2x(selectany); // Known attribute not supported in C mode
 
@@ -27,10 +36,10 @@
 // CHECK: maybe_unused: 202106L
 C2x(maybe_unused)
 
-// CHECK: __gnu__::warn_unused_result: 202003L
+// CHECK: __gnu__::warn_unused_result: 1
 C2x(__gnu__::warn_unused_result)
 
-// CHECK: gnu::__warn_unused_result__: 202003L
+// CHECK: gnu::__warn_unused_result__: 1
 C2x(gnu::__warn_unused_result__)
 
 // Test that macro expansion of the builtin argument works.