Implement #pragma pack use in structure packing. The general approach
is to encode the state of the #pragma pack stack as an attribute when
the structure is declared.
- Extend PackedAttr to take an alignment (in bits), and reuse for
both __attribute__((packed)) (which takes no argument, instead
packing tightly (to "minimize the memory required") and for #pragma
pack (which allows specification of the maximum alignment in
bytes). __attribute__((packed)) is just encoded as Alignment=1.
This conflates two related but different mechanisms, but it didn't
seem worth another attribute.
- I have attempted to follow the MSVC semantics as opposed to the gcc
ones, since if I understand correctly #pragma pack originated with
MSVC. The semantics are generally equivalent except when the stack
is altered during the definition of a structure; its not clear if
anyone does this in practice. See testcase if curious.
llvm-svn: 57623
diff --git a/clang/test/Sema/pragma-pack-2.c b/clang/test/Sema/pragma-pack-2.c
new file mode 100644
index 0000000..e139be0
--- /dev/null
+++ b/clang/test/Sema/pragma-pack-2.c
@@ -0,0 +1,66 @@
+// RUN: clang -triple i686-apple-darwin9 %s -fsyntax-only -verify
+
+#include <stddef.h>
+
+#pragma pack(4)
+
+// Baseline
+struct s0 {
+ char f0;
+ int f1;
+};
+extern int a0[offsetof(struct s0, f1) == 4 ? 1 : -1];
+
+#pragma pack(push, 2)
+struct s1 {
+ char f0;
+ int f1;
+};
+extern int a1[offsetof(struct s1, f1) == 2 ? 1 : -1];
+#pragma pack(pop)
+
+// Test scope of definition
+
+#pragma pack(push, 2)
+struct s2_0 {
+#pragma pack(pop)
+ char f0;
+ int f1;
+};
+extern int a2_0[offsetof(struct s2_0, f1) == 2 ? 1 : -1];
+
+struct s2_1 {
+ char f0;
+#pragma pack(push, 2)
+ int f1;
+#pragma pack(pop)
+};
+extern int a2_1[offsetof(struct s2_1, f1) == 4 ? 1 : -1];
+
+struct s2_2 {
+ char f0;
+ int f1;
+#pragma pack(push, 2)
+};
+#pragma pack(pop)
+extern int a2_2[offsetof(struct s2_2, f1) == 4 ? 1 : -1];
+
+struct s2_3 {
+ char f0;
+#pragma pack(push, 2)
+ struct s2_3_0 {
+#pragma pack(pop)
+ int f0;
+ } f1;
+};
+extern int a2_3[offsetof(struct s2_3, f1) == 2 ? 1 : -1];
+
+struct s2_4 {
+ char f0;
+ struct s2_4_0 {
+ int f0;
+#pragma pack(push, 2)
+ } f1;
+#pragma pack(pop)
+};
+extern int a2_4[offsetof(struct s2_4, f1) == 4 ? 1 : -1];