Add the alloc_size attribute to clang.

This patch does three things:

- Gives us the alloc_size attribute in clang, which lets us infer the
  number of bytes handed back to us by malloc/realloc/calloc/any user
  functions that act in a similar manner.
- Teaches our constexpr evaluator that evaluating some `const` variables
  is OK sometimes. This is why we have a change in
  test/SemaCXX/constant-expression-cxx11.cpp and other seemingly
  unrelated tests. Richard Smith okay'ed this idea some time ago in
  person.
- Uniques some Blocks in CodeGen, which was reviewed separately at
  D26410. Lack of uniquing only really shows up as a problem when
  combined with our new eagerness in the face of const.

Differential Revision: https://reviews.llvm.org/D14274


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290149 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 0 deletions

diff --git a/include/clang/Basic/Attr.td b/include/clang/Basic/Attr.td
index 4c8276a553..f6a5e54b2b 100644
--- a/include/clang/Basic/Attr.td
+++ b/include/clang/Basic/Attr.td
@@ -780,6 +780,15 @@ def EmptyBases : InheritableAttr, TargetSpecificAttr<TargetMicrosoftCXXABI> {
   let Documentation = [EmptyBasesDocs];
 }
 
+def AllocSize : InheritableAttr {
+  let Spellings = [GCC<"alloc_size">];
+  let Subjects = SubjectList<[HasFunctionProto], WarnDiag,
+                             "ExpectedFunctionWithProtoType">;
+  let Args = [IntArgument<"ElemSizeParam">, IntArgument<"NumElemsParam", 1>];
+  let TemplateDependent = 1;
+  let Documentation = [AllocSizeDocs];
+}
+
 def EnableIf : InheritableAttr {
   let Spellings = [GNU<"enable_if">];
   let Subjects = SubjectList<[Function]>;