[LLVMbugs] [Bug 17772] New: [-cxx-abi microsoft] One-element arrays laid out wrong

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17772

            Bug ID: 17772
           Summary: [-cxx-abi microsoft] One-element arrays laid out wrong
           Product: clang
           Version: trunk
          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

the file in question:

#include <stddef.h>
#include <stdio.h>
#include <string.h>
char buffer[419430400];
inline void *operator new(size_t, void *pv) { return pv; }
struct TypeName0 {
        char TypeName0FieldName0;
        TypeName0() {
                printf("TypeName0 (this): %llu\n", (unsigned long
long)((size_t)this - (size_t)buffer));
                printf("TypeName0 (fiel): %llu\n", (unsigned long
long)((size_t)&TypeName0FieldName0 - (size_t)buffer));
        }
};
struct TypeName2: public virtual TypeName0 {
        double TypeName2FieldName1;
        TypeName2() {
                printf("TypeName2 (this): %llu\n", (unsigned long
long)((size_t)this - (size_t)buffer));
                printf("TypeName2 (fiel): %llu\n", (unsigned long
long)((size_t)&TypeName2FieldName1 - (size_t)buffer));
        }
};
struct TypeName3: public virtual TypeName0 {
        TypeName2 TypeName3FieldName2[1];
        char TypeName3FieldName3;
        TypeName3() {
                printf("TypeName3 (this): %llu\n", (unsigned long
long)((size_t)this - (size_t)buffer));
                printf("TypeName3 (fiel): %llu\n", (unsigned long
long)((size_t)&TypeName3FieldName2 - (size_t)buffer));
                printf("TypeName3 (fiel): %llu\n", (unsigned long
long)((size_t)&TypeName3FieldName3 - (size_t)buffer));
        }
};
int main() {
        memset(buffer, 0, sizeof(buffer));
        new (buffer) TypeName3;
}


vs:
TypeName0 (this): 32 
TypeName0 (fiel): 32
TypeName0 (this): 24
TypeName0 (fiel): 24
TypeName2 (this): 8
TypeName2 (fiel): 16
TypeName3 (this): 0
TypeName3 (fiel): 8
TypeName3 (fiel): 25

clang:
TypeName0 (this): 40
TypeName0 (fiel): 40
TypeName0 (this): 24
TypeName0 (fiel): 24
TypeName2 (this): 8
TypeName2 (fiel): 16
TypeName3 (this): 0
TypeName3 (fiel): 8
TypeName3 (fiel): 32

We are layout compatible if the "[1]" is removed.

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