[LLVMbugs] [Bug 7310] New: Wrong ABI on ARM for classes with non trivial copy constructors

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Mon Jun 7 12:00:32 CDT 2010


http://llvm.org/bugs/show_bug.cgi?id=7310

           Summary: Wrong ABI on ARM for classes with non trivial copy
                    constructors
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: rafael.espindola at gmail.com
                CC: llvmbugs at cs.uiuc.edu, dgregor at apple.com


The code

-------------------
class SMLoc {
 const char *Ptr;
public:
 SMLoc(const SMLoc &RHS);
};
SMLoc foo(void *p);
void bar(void *x) {
 foo(x);
}
------------------

Produces

declare arm_aapcscc i32 @_Z3fooPv(i8*) optsize

but

http://www.codesourcery.com/public/cxx-abi/abi.html

in 3.1.4 Return Values  says


In general, C++ return values are handled just like C return values.
This includes class type results returned in registers. However, if
the return value type has a non-trivial copy constructor or
destructor, the caller allocates space for a temporary, and passes a
pointer to the temporary as an implicit first parameter preceding both
the this parameter and user parameters. The callee constructs the
return value into this temporary.

Is this also true on Darwin or should I special case this for non-Darwin
systems?

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