Implement [dcl.align]p5 and C11 6.7.5/4: alignas cannot underalign.

Also support alignas(0), which C++11 and C11 require us to ignore.

llvm-svn: 174157

3 files changed, 76 insertions, 2 deletions

diff --git a/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp b/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp
new file mode 100644
index 00000000000..10be98d16ea
--- /dev/null
+++ b/clang/test/CXX/dcl.dcl/dcl.attr/dcl.align/p5.cpp
@@ -0,0 +1,74 @@
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-linux-gnu -verify %s
+
+alignas(1) int n1; // expected-error {{requested alignment is less than minimum alignment of 4 for type 'int'}}
+alignas(1) alignas(2) int n2; // expected-error {{less than minimum alignment}}
+alignas(1) alignas(2) alignas(4) int n3; // ok
+alignas(1) alignas(2) alignas(0) int n4; // expected-error {{less than minimum alignment}}
+alignas(1) alignas(2) int n5 alignas(4); // ok
+alignas(1) alignas(4) int n6 alignas(2); // ok
+alignas(1) int n7 alignas(2), // expected-error {{less than minimum alignment}}
+               n8 alignas(4); // ok
+alignas(8) int n9 alignas(2); // ok, overaligned
+
+enum alignas(1) E1 {}; // expected-error {{requested alignment is less than minimum alignment of 4 for type 'E1'}}
+enum alignas(1) E2 : char {}; // ok
+enum alignas(4) E3 { e3 = 0 }; // ok
+enum alignas(4) E4 { e4 = 1ull << 33 }; // expected-error {{requested alignment is less than minimum alignment of 8 for type 'E4'}}
+
+struct S1 {
+  alignas(8) int n;
+};
+struct alignas(2) S2 { // expected-error {{requested alignment is less than minimum alignment of 4 for type 'S2'}}
+  int n;
+};
+struct alignas(2) S3 { // expected-error {{requested alignment is less than minimum alignment of 8 for type 'S3'}}
+  S1 s1;
+};
+struct alignas(2) S4 : S1 { // expected-error {{requested alignment is less than minimum alignment of 8 for type 'S4'}}
+};
+struct S5 : S1 {
+  alignas(2) S1 s1; // expected-error {{requested alignment is less than minimum alignment of 8 for type 'S1'}}
+};
+struct S6 {
+  S1 s1;
+};
+struct S7 : S1 {
+};
+struct alignas(2) alignas(8) alignas(1) S8 : S1 {
+};
+
+S1 s1 alignas(4); // expected-error {{requested alignment is less than minimum alignment of 8 for type 'S1'}}
+S6 s6 alignas(4); // expected-error {{requested alignment is less than minimum alignment of 8 for type 'S6'}}
+S7 s7 alignas(4); // expected-error {{requested alignment is less than minimum alignment of 8 for type 'S7'}}
+
+template<int N, int M, typename T>
+struct alignas(N) X { // expected-error 3{{requested alignment is less than minimum}}
+  alignas(M) T t; // expected-error 3{{requested alignment is less than minimum}}
+};
+
+template struct X<1, 1, char>;
+template struct X<4, 1, char>;
+template struct X<1, 2, char>; // expected-note {{instantiation}}
+template struct X<1, 1, short>; // expected-note {{instantiation}}
+template struct X<2, 1, short>; // expected-note {{instantiation}}
+template struct X<2, 2, short>;
+template struct X<16, 8, S1>;
+template struct X<4, 4, S1>; // expected-note {{instantiation}}
+
+template<int N, typename T>
+struct Y {
+  enum alignas(N) E : T {}; // expected-error {{requested alignment is less than minimum}}
+};
+template struct Y<1, char>;
+template struct Y<2, char>;
+template struct Y<1, short>; // expected-note {{instantiation}}
+template struct Y<2, short>;
+
+template<int N, typename T>
+void f() {
+  alignas(N) T v; // expected-error {{requested alignment is less than minimum}}
+};
+template void f<1, char>();
+template void f<2, char>();
+template void f<1, short>(); // expected-note {{instantiation}}
+template void f<2, short>();
diff --git a/clang/test/Sema/alignas.c b/clang/test/Sema/alignas.c
index b5e87cf4b72..a79c738d12d 100644
--- a/clang/test/Sema/alignas.c
+++ b/clang/test/Sema/alignas.c
@@ -3,7 +3,7 @@
 
 _Alignas(3) int align_illegal; //expected-error {{requested alignment is not a power of 2}}
 _Alignas(int) char align_big;
-_Alignas(1) int align_small; // FIXME: this should be rejected
+_Alignas(1) int align_small; // expected-error {{requested alignment is less than minimum}}
 _Alignas(1) unsigned _Alignas(8) int _Alignas(1) align_multiple;
 
 struct align_member {
diff --git a/clang/test/SemaCXX/attr-cxx0x.cpp b/clang/test/SemaCXX/attr-cxx0x.cpp
index d038e637f4e..09103c8907a 100644
--- a/clang/test/SemaCXX/attr-cxx0x.cpp
+++ b/clang/test/SemaCXX/attr-cxx0x.cpp
@@ -2,7 +2,7 @@
 
 int align_illegal alignas(3); //expected-error {{requested alignment is not a power of 2}}
 char align_big alignas(int);
-int align_small alignas(1); // FIXME: this should be rejected
+int align_small alignas(1); // expected-error {{requested alignment is less than minimum}}
 int align_multiple alignas(1) alignas(8) alignas(1);
 alignas(4) int align_before;