[PATCH] D14274: Add alloc_size attribute to clang

[George Burgess IV via cfe-commits]

george.burgess.iv created this revision.
george.burgess.iv added a reviewer: rsmith.
george.burgess.iv added a subscriber: cfe-commits.

This is the first in a two patch series aimed at adding the alloc_size attribute to clang. This patch adds the alloc_size attribute, docs, and all of the logic needed to handle it in ExprConstant. The only thing that's _really_ missing is our ability to handle non-const locals, because that's proving to be a moderately interesting challenge. (Spoiler alert: that's basically the only thing in patch #2)

There's also a restructuring of TryEvaluateBuiltinObjectSize thrown in, because I felt like it was getting overly subtle. Hopefully the new version is considerably easier to reason about. :)

— Implementation notes —
- With the restructuring of TryEvaluateBuiltinObjectSize, I was able to make EM_DesignatorFold (now EM_OffsetFold) the only EvalMode we use in evaluating __builtin_object_size.

- The InvalidBase functionality of LValues was further (ab)used to get information to TryEvaluateBuiltinObjectSize. We know an LValue has been initialized by an alloc_size function if the base is invalid and the base itself is a CallExpr. This won’t conflict with current behavior, because (prior to this patch) all invalid bases were MemberExprs.

- As said in the ExprConstant code, I’d love a less hand-wavy approach to writing tryEvaluateLValueAsAllocSize.

http://reviews.llvm.org/D14274

Files:
  include/clang/Basic/Attr.td
  include/clang/Basic/AttrDocs.td
  include/clang/Basic/DiagnosticSemaKinds.td
  lib/AST/ExprConstant.cpp
  lib/Sema/SemaDeclAttr.cpp
  test/CodeGen/alloc-size.c
  test/Sema/alloc-size.c

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