Support `guarded_by` attribute and related attributes inside C structs and support late parsing them (#95455)

This fixes #20777. This replaces #94216 which was reverted after being
merged.

Previously the `guarded_by`, `pt_guarded_by`, `acquired_after`, and
`acquired_before` attributes were only supported inside C++ classes or
top level C/C++ declaration.

This patch allows these attributes to be added to struct members in C.
These attributes have also now support experimental late parsing. This
is off by default but can be enabled by passing
`-fexperimental-late-parse-attributes`. This is useful for referring to
a struct member after the annotated member. E.g.

```
struct Example {
  int a_value_defined_before __attribute__ ((guarded_by(a_mutex)));
  struct Mutex *a_mutex;
};
```

1 files changed, 10 insertions, 5 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index a07f7ad..0aae5f3 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -593,7 +593,9 @@ unsigned Parser::ParseAttributeArgsCommon(
           EnterExpressionEvaluationContext Unevaluated(
               Actions,
               Uneval ? Sema::ExpressionEvaluationContext::Unevaluated
-                     : Sema::ExpressionEvaluationContext::ConstantEvaluated);
+                     : Sema::ExpressionEvaluationContext::ConstantEvaluated,
+              nullptr,
+              Sema::ExpressionEvaluationContextRecord::EK_AttrArgument);
 
           ExprResult ArgExpr(
               Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression()));
@@ -610,9 +612,12 @@ unsigned Parser::ParseAttributeArgsCommon(
       // General case. Parse all available expressions.
       bool Uneval = attributeParsedArgsUnevaluated(*AttrName);
       EnterExpressionEvaluationContext Unevaluated(
-          Actions, Uneval
-                       ? Sema::ExpressionEvaluationContext::Unevaluated
-                       : Sema::ExpressionEvaluationContext::ConstantEvaluated);
+          Actions,
+          Uneval ? Sema::ExpressionEvaluationContext::Unevaluated
+                 : Sema::ExpressionEvaluationContext::ConstantEvaluated,
+          nullptr,
+          Sema::ExpressionEvaluationContextRecord::ExpressionKind::
+              EK_AttrArgument);
 
       ExprVector ParsedExprs;
       ParsedAttributeArgumentsProperties ArgProperties =
@@ -3383,7 +3388,7 @@ void Parser::ParseBoundsAttribute(IdentifierInfo &AttrName,
       Sema::ExpressionEvaluationContextRecord::ExpressionKind;
   EnterExpressionEvaluationContext EC(
       Actions, Sema::ExpressionEvaluationContext::PotentiallyEvaluated, nullptr,
-      ExpressionKind::EK_BoundsAttrArgument);
+      ExpressionKind::EK_AttrArgument);
 
   ExprResult ArgExpr(
       Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression()));