Debug info for imported declarations sometimes reference empty DIEs · Issue #51501 · llvm/llvm-project (original) (raw)

Extended Description

When an imported declaration references a function that has been inlined and removed, its DIE will reference an empty subprogram DIE.

In clang, it creates a new empty DIE rather than using the existing abstract origin DIE.

$ cat main.cpp
namespace ns {
inline __attribute__((always_inline))
void foo() { int a = 4; }
}

void goo() {
  using ns::foo;
  foo();
}
$ clang -g main.cpp -c -o - | llvm-dwarfdump -
0x0000000b: DW_TAG_compile_unit
...

0x0000002a:   DW_TAG_namespace
                DW_AT_name	("ns")

0x0000002f:     DW_TAG_subprogram
                  DW_AT_linkage_name	("_ZN2ns3fooEv")
                  DW_AT_name	("foo")
                  DW_AT_decl_line	(3)
                  DW_AT_external	(true)
                  DW_AT_inline	(DW_INL_inlined)

0x0000003b:       DW_TAG_variable
                    DW_AT_name	("a")
                    DW_AT_decl_line	(3)
                    DW_AT_type	(0x00000049 "int")

0x00000046:       NULL

0x00000047:     DW_TAG_subprogram

0x00000048:     NULL

0x00000050:   DW_TAG_subprogram
                DW_AT_low_pc	(0x0000000000000000)
                DW_AT_high_pc	(0x000000000000000d)
                DW_AT_frame_base	(DW_OP_reg6 RBP)
                DW_AT_linkage_name	("_Z3goov")
                DW_AT_name	("goo")
                DW_AT_decl_line	(6)
                DW_AT_external	(true)

0x00000069:     DW_TAG_imported_declaration
                  DW_AT_decl_line	(7)
                  DW_AT_import	(0x00000047)

0x00000070:     DW_TAG_inlined_subroutine
                  DW_AT_abstract_origin	(0x0000002f "_ZN2ns3fooEv")
                  DW_AT_low_pc	(0x0000000000000004)
                  DW_AT_high_pc	(0x000000000000000b)
                  DW_AT_call_line	(8)
                  DW_AT_call_column	(0x03)

0x00000084:       DW_TAG_variable
                    DW_AT_location	(DW_OP_fbreg -4)
                    DW_AT_abstract_origin	(0x0000003b "a")

0x0000008c:       NULL

0x0000008d:     NULL

0x0000008e:   NULL