[PATCH] D34050: Support capturing the implicit `this` argument to C++ class member functions

[Dean Michael Berris via Phabricator via llvm-commits]

dberris created this revision.

Before this change, we couldn't capture the `this` pointer that's
implicitly the first argument of class member functions. There are some
interesting things we can do with capturing even just this single
argument for zero-argument member functions.


https://reviews.llvm.org/D34050

Files:
  lib/Sema/SemaDeclAttr.cpp
  test/Sema/xray-log-args-class.cpp


Index: test/Sema/xray-log-args-class.cpp
===================================================================
--- /dev/null
+++ test/Sema/xray-log-args-class.cpp
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only -std=c++11 -x c++
+
+class Class {
+  [[clang::xray_always_instrument, clang::xray_log_args(1)]] void Method();
+  [[clang::xray_log_args(-1)]] void Invalid(); // expected-error {{'xray_log_args' attribute parameter 1 is out of bounds}}
+  [[clang::xray_log_args("invalid")]] void InvalidStringArg(); // expected-error {{'xray_log_args'}}
+};
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -4604,14 +4604,40 @@
 static void handleXRayLogArgsAttr(Sema &S, Decl *D,
                                   const AttributeList &Attr) {
   uint64_t ArgCount;
+
+  // Treat member functions especially, since we do want to support saving the
+  // implicit this argument for member functions.
+  if (isInstanceMethod(D)) {
+    auto *IdxExpr = Attr.getArgAsExpr(0);
+    llvm::APSInt IdxInt;
+    if (!IdxExpr->isIntegerConstantExpr(IdxInt, S.Context)) {
+      S.Diag(getAttrLoc(Attr), diag::err_attribute_argument_n_type)
+          << getAttrName(Attr) << 1u << AANT_ArgumentIntegerConstant
+          << IdxExpr->getSourceRange();
+      return;
+    }
+    ArgCount = IdxInt.getLimitedValue();
+    bool HP = hasFunctionProto(D);
+    unsigned NumParams = HP ? getFunctionOrMethodNumParams(D) + 1 : 1;
+    if (ArgCount > NumParams) {
+      S.Diag(getAttrLoc(Attr), diag::err_attribute_argument_out_of_bounds)
+          << getAttrName(Attr) << 1 << IdxExpr->getSourceRange();
+      return;
+    }
+    D->addAttr(::new (S.Context)
+                   XRayLogArgsAttr(Attr.getRange(), S.Context, ArgCount,
+                                   Attr.getAttributeSpellingListIndex()));
+    return;
+  }
+
   if (!checkFunctionOrMethodParameterIndex(S, D, Attr, 1, Attr.getArgAsExpr(0),
                                            ArgCount))
     return;
 
   // ArgCount isn't a parameter index [0;n), it's a count [1;n] - hence + 1.
   D->addAttr(::new (S.Context)
-             XRayLogArgsAttr(Attr.getRange(), S.Context, ++ArgCount,
-             Attr.getAttributeSpellingListIndex()));
+                 XRayLogArgsAttr(Attr.getRange(), S.Context, ++ArgCount,
+                                 Attr.getAttributeSpellingListIndex()));
 }
 
 //===----------------------------------------------------------------------===//


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