[llvm-dev] Debug info scope of explicit casting type does not seem correct

[Aboud, Amjad via llvm-dev]

Hi,
I am wondering if this behavior of creating debug info is correct.
A type in compile unit entry is pointing to a type under subprogram entry?!

This is the root cause of https://llvm.org/bugs/show_bug.cgi?id=27579

0x0000000b: DW_TAG_compile_unit [1] *

0x00000026:   DW_TAG_pointer_type [2]
                            DW_AT_type [DW_FORM_ref4]       (cu + 0x002c => {0x0000002c})

0x0000002b:   DW_TAG_subprogram [3] *

0x0000002c:     DW_TAG_typedef [4]
                               DW_AT_type [DW_FORM_ref4]     (cu + 0x0040 => {0x00000040})
                               DW_AT_name [DW_FORM_strp]     ( .debug_str[0x00000060] = "T")
                               DW_AT_decl_file [DW_FORM_data1]       ("c:\temp\ICL\LB\retain.cpp")
                               DW_AT_decl_line [DW_FORM_data1]       (16)

0x00000037:     NULL


command line:
clang -cc1 -triple i386-apple-ios9.0.0 -emit-obj -debug-info-kind=limited -O2 test.cpp -o - | llvm-dwarfdump -debug-dump=info -

> cat test.cpp
class A {
public:
  int x;
};


class B {
public:
  typedef A type;
};

template<typename X>
int foo(void* in) {
  typedef typename X::type T;
  const T* p = (T*) in;
  return p->x;
}

int bar() {
A a;
  return foo<B>(&a);
}

Reason for this behavior is the explicit cast "(T*)", which leads into the following IR:

!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.9.0 (trunk 267335)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3)
!3 = !{!4}
!4 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !5, size: 32, align: 32)  <----------------- No Scope, leads to compile unit scope!!
!5 = !DIDerivedType(tag: DW_TAG_typedef, name: "T", scope: !7, file: !6, line: 16, baseType: !20)
!7 = distinct !DISubprogram(name: "foo<B>", linkageName: "_Z3fooI1BEiPv", scope: !6, file: !6, line: 15, type: !8, isLocal: false, isDefinition: true, scopeLine: 15, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !12, variables: !15)


Thanks,
Amjad

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