[LLVMbugs] [Bug 18618] New: MS ABI: Alignment of pointer to member is wrong

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18618

            Bug ID: 18618
           Summary: MS ABI: Alignment of pointer to member is wrong
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: david.majnemer at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

consider:
extern "C" int printf(const char *, ...);
static char buffer[419430400];
inline void *operator new(size_t, void *pv) { return pv; }
struct __single_inheritance Single;
struct __multiple_inheritance Multiple;
struct __virtual_inheritance Virtual;
struct Unspecified;
struct C {
  char c;
  int Single::*Single_field;
  int Multiple::*Multiple_field;
  int Virtual::*Virtual_field;
  int Unspecified::*Unspecified_field;

  int (Single::*Single_fun)();
  int (Multiple::*Multiple_fun)();
  int (Virtual::*Virtual_fun)();
  int (Unspecified::*Unspecified_fun)();
  C() {
    printf("offsetof Single_field         %d\n", (int)((char *)&Single_field -
buffer));
    printf("alignof  Single_field         %d\n", __alignof(Single_field));
    printf("alignof  int Single::*        %d\n", __alignof(int Single::*));

    printf("offsetof Multiple_field       %d\n", (int)((char *)&Multiple_field
- buffer));
    printf("alignof  Multiple_field       %d\n", __alignof(Multiple_field));
    printf("alignof  int Multiple::*      %d\n", __alignof(int Multiple::*));

    printf("offsetof Virtual_field        %d\n", (int)((char *)&Virtual_field -
buffer));
    printf("alignof  Virtual_field        %d\n", __alignof(Virtual_field));
    printf("alignof  int Virtual::*       %d\n", __alignof(int Virtual::*));

    printf("offsetof Unspecified_field    %d\n", (int)((char
*)&Unspecified_field - buffer));
    printf("alignof  Unspecified_field    %d\n", __alignof(Unspecified_field));
    printf("alignof  int Unspecified::*   %d\n", __alignof(int
Unspecified::*));

    printf("offsetof Single_fun           %d\n", (int)((char *)&Single_fun -
buffer));                                                                       
    printf("alignof  Single_fun           %d\n", __alignof(Single_fun));
    printf("alignof  int (Single::*)()    %d\n", __alignof(int (Single::*)()));

    printf("offsetof Multiple_fun         %d\n", (int)((char *)&Multiple_fun -
buffer));
    printf("alignof  Multiple_fun         %d\n", __alignof(Multiple_fun));
    printf("alignof  int (Multiple::*)()  %d\n", __alignof(int
(Multiple::*)()));

    printf("offsetof Virtual_fun          %d\n", (int)((char *)&Virtual_fun -
buffer));
    printf("alignof  Virtual_fun          %d\n", __alignof(Virtual_fun));
    printf("alignof  int (Virtual::*)     %d\n", __alignof(int
(Virtual::*)()));

    printf("offsetof Unspecified_fun      %d\n", (int)((char *)&Unspecified_fun
- buffer));                                                                     
    printf("alignof  Unspecified_fun      %d\n", __alignof(Unspecified_fun));
    printf("alignof  int (Unspecified::*) %d\n", __alignof(int
(Unspecified::*)()));                                                           
  }
};
int main() { new (buffer) C; }

clang gets:
offsetof Single_field         4
alignof  Single_field         4
alignof  int Single::*        4
offsetof Multiple_field       8
alignof  Multiple_field       4
alignof  int Multiple::*      4
offsetof Virtual_field        12
alignof  Virtual_field        4
alignof  int Virtual::*       4
offsetof Unspecified_field    20
alignof  Unspecified_field    4
alignof  int Unspecified::*   4
offsetof Single_fun           32
alignof  Single_fun           4
alignof  int (Single::*)()    4
offsetof Multiple_fun         36
alignof  Multiple_fun         4
alignof  int (Multiple::*)()  4
offsetof Virtual_fun          44
alignof  Virtual_fun          4
alignof  int (Virtual::*)     4
offsetof Unspecified_fun      56
alignof  Unspecified_fun      4
alignof  int (Unspecified::*) 4

msvc gets:
offsetof Single_field         4
alignof  Single_field         1
alignof  int Single::*        4
offsetof Multiple_field       8
alignof  Multiple_field       1
alignof  int Multiple::*      4
offsetof Virtual_field        16
alignof  Virtual_field        1
alignof  int Virtual::*       4
offsetof Unspecified_field    24
alignof  Unspecified_field    1
alignof  int Unspecified::*   4
offsetof Single_fun           36
alignof  Single_fun           1
alignof  int (Single::*)()    4
offsetof Multiple_fun         40
alignof  Multiple_fun         1
alignof  int (Multiple::*)()  4
offsetof Virtual_fun          48
alignof  Virtual_fun          1
alignof  int (Virtual::*)     4
offsetof Unspecified_fun      64
alignof  Unspecified_fun      1
alignof  int (Unspecified::*) 4

note that alignof on a field in the struct is different from the field's type.

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