[LLVMbugs] [Bug 4095] New: transparent_union modeled wrong

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=4095

           Summary: transparent_union modeled wrong
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Semantic Analyzer
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: clattner at apple.com
                CC: llvmbugs at cs.uiuc.edu


It looks like we handle transparent union arguments by claiming a function
takes a void*, which leads to sema problems.  Here's a simple testcase:

struct d_object_s {
    int x;
};
typedef union {
    struct d_object_s *_do;
} d_object_t __attribute__((transparent_union));
void test(d_object_t _head) {
  d_object_t x;
  x;
  struct d_object_s *head = _head._do;
}

---

We reject the "head =" line with:
t.c:13:35: error: member reference base type 'd_object_t' (aka 'void *const')
is not a structure or union
  struct d_object_s *head = _head._do;
                            ~~~~~ ^

Looking at the -ast-dump, it looks like dispatch_object_t is just a typedef for
void* in the AST (!):

void _dispatch_queue_push_list(dispatch_object_t _head)
(CompoundStmt 0x26037d0 <t.c:10:1, line:14:1>
  (DeclStmt 0x26040e0 <line:11:3, col:22>
    0x2604040 "dispatch_object_t x"
  (DeclRefExpr 0x2604100 <line:12:3> 'dispatch_object_t':'void *' Var='x'
0x2604040)
  (DeclStmt 0x2604190 <line:13:3, col:41>
    0x2604120 "struct dispatch_object_s *head =
      (ImplicitCastExpr 0x2604170 <col:36> 'struct dispatch_object_s *'
        (DeclRefExpr 0x2604150 <col:36> 'dispatch_object_t':'void *'
ParmVar='_head' 0x2603fd0))")


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