Add the alloc_size attribute to clang, attempt 2.

This is a recommit of r290149, which was reverted in r290169 due to msan
failures. msan was failing because we were calling
`isMostDerivedAnUnsizedArray` on an invalid designator, which caused us
to read uninitialized memory. To fix this, the logic of the caller of
said function was simplified, and we now have a `!Invalid` assert in
`isMostDerivedAnUnsizedArray`, so we can catch this particular bug more
easily in the future.

Fingers crossed that this patch sticks this time. :)

Original commit message:

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.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290297 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 2 deletions

diff --git a/test/SemaCXX/constant-expression-cxx11.cpp b/test/SemaCXX/constant-expression-cxx11.cpp
index 0b7528281a..9ec8318b9e 100644
--- a/test/SemaCXX/constant-expression-cxx11.cpp
+++ b/test/SemaCXX/constant-expression-cxx11.cpp
@@ -1183,7 +1183,7 @@ constexpr int m1b = const_cast<const int&>(n1); // expected-error {{constant exp
 constexpr int m2b = const_cast<const int&>(n2); // expected-error {{constant expression}} expected-note {{read of volatile object 'n2'}}
 
 struct T { int n; };
-const T t = { 42 }; // expected-note {{declared here}}
+const T t = { 42 };
 
 constexpr int f(volatile int &&r) {
   return r; // expected-note {{read of volatile-qualified type 'volatile int'}}
@@ -1195,7 +1195,7 @@ struct S {
   int j : f(0); // expected-error {{constant expression}} expected-note {{in call to 'f(0)'}}
   int k : g(0); // expected-error {{constant expression}} expected-note {{temporary created here}} expected-note {{in call to 'g(0)'}}
   int l : n3; // expected-error {{constant expression}} expected-note {{read of non-const variable}}
-  int m : t.n; // expected-error {{constant expression}} expected-note {{read of non-constexpr variable}}
+  int m : t.n; // expected-warning{{width of bit-field 'm' (42 bits)}}
 };
 
 }