[LLVMbugs] [Bug 22892] New: Debug info for function argument missing DW_AT_location

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=22892

            Bug ID: 22892
           Summary: Debug info for function argument missing
                    DW_AT_location
           Product: new-bugs
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: bruce.mitchener at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 14038
  --> https://llvm.org/bugs/attachment.cgi?id=14038&action=edit
Example C code that demonstrates the issue

When I compile the attached code, the "args_" argument to
"Khandle_missed_dispatchVKgI" is missing a DW_AT_location.

This is a test case isolated from a much larger body of code (where this
happens more often). This code is also generated from our C back-end. It is
interesting (to me at least) that the code generated by our LLVM back-end has
the same problem.

I compile with clang 3.5, 3.6 or the most recent release from Apple:

    clang -arch i386 -g -O -c -o bad-debug-info.o bad-debug-info.c

and then I run dwarfdump (or llvm-dwarfdump) and see:

0x000005f4:   DW_TAG_subprogram [18] *
                DW_AT_low_pc [DW_FORM_addr] (0x0000000000000030)
                DW_AT_high_pc [DW_FORM_addr]  (0x000000000000028e)
                DW_AT_frame_base [DW_FORM_block1] (<0x01> 55 )
                DW_AT_name [DW_FORM_strp] ( .debug_str[0x00000447] =
"Khandle_missed_dispatchVKgI")
                DW_AT_decl_file [DW_FORM_data1]
("/Users/bruce/Development/dylan/missing-debug-location/new-dispatch.c")
                DW_AT_decl_line [DW_FORM_data1] (105)
                DW_AT_prototyped [DW_FORM_flag] (0x01)
                DW_AT_type [DW_FORM_ref4] (cu + 0x0127 => {0x00000127})
                DW_AT_external [DW_FORM_flag] (0x01)
                DW_AT_APPLE_optimized [DW_FORM_flag]  (0x01)

0x0000060c:     DW_TAG_formal_parameter [24]
                  DW_AT_location [DW_FORM_data4]  (0x00000000)
                  DW_AT_name [DW_FORM_strp] ( .debug_str[0x00000480] = "d_")
                  DW_AT_decl_file [DW_FORM_data1]
("/Users/bruce/Development/dylan/missing-debug-location/new-dispatch.c")
                  DW_AT_decl_line [DW_FORM_data1] (105)
                  DW_AT_type [DW_FORM_ref4] (cu + 0x0127 => {0x00000127})

0x0000061b:     DW_TAG_formal_parameter [24]
                  DW_AT_location [DW_FORM_data4]  (0x000000fc)
                  DW_AT_name [DW_FORM_strp] ( .debug_str[0x0000046f] =
"parent_")
                  DW_AT_decl_file [DW_FORM_data1]
("/Users/bruce/Development/dylan/missing-debug-location/new-dispatch.c")
                  DW_AT_decl_line [DW_FORM_data1] (105)
                  DW_AT_type [DW_FORM_ref4] (cu + 0x0127 => {0x00000127})

0x0000062a:     DW_TAG_formal_parameter [25]
                  DW_AT_name [DW_FORM_strp] ( .debug_str[0x0000047a] = "args_")
                  DW_AT_decl_file [DW_FORM_data1]
("/Users/bruce/Development/dylan/missing-debug-location/new-dispatch.c")
                  DW_AT_decl_line [DW_FORM_data1] (105)
                  DW_AT_type [DW_FORM_ref4] (cu + 0x0127 => {0x00000127})

When I use llvm-dwarfdump, I get a bunch of error messages (and more on 3.6
than on 3.5). I don't get any messages when using the system dwarfdump.

I believe that gcc is generating correct debug info for this code.

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