Fix how ValueObjectChild handles bit-fields stored in a Scalar in UpdateValue()

[shafik]

Summary

When bit-field data was stored in a Scalar in ValueObjectChild during UpdateValue() it was extracting the bit-field value. Later on in lldb_private::DumpDataExtractor(…) we were again attempting to extract the bit-field:

s->Printf("%" PRIu64,
            DE.GetMaxU64Bitfield(&offset, item_byte_size, item_bit_size,
                                 item_bit_offset));

which would then not obtain the correct value. This will remove the extra extraction in UpdateValue().

We hit this specific case when values are passed in registers, which we could only reproduce in an optimized build.

[shafik]

Note: for the test I did not want to rely on clang choosing to pass the union by register, so I used assembly which ensures I will obtain the behavior I am looking to capture for the test.

[friss]

lldb/source/Core/ValueObjectChild.cpp

202–205

Why remove the code in ValueObject rather than avoid re-extracting at printing time? I'm not sure which one is correct. If you get your hands on a ValueObject for the field in your test, what will GetValueAsUnsigned return? it should give the correct field value.

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/TestValueObjPassByRef.py

11

If the test in assembly is what we want, this is also architecture specific. It should be restricted to x86_64

[davide]

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/Makefile

3

This is fundamentally a no-go. Depending on the optimization pipeline passes this in a register is an assumption that might go away at some point in the future and this test won't test what it has to & will still pass silently.

Something like this might work:
https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html

[davide]

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/Makefile

3

*depending on the optimization pipeline, the fact that is passed in a register is an assumption that

[aprantl]

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/Makefile

2

I think this is redundant. The default is a.out

3

Given that the source code is a .s file, I think the -O1 is just redundant and can be removed. Using assembler is fine for this purpose.

9

Is it possible to just override the rule that produces the .o file? Otherwise you are dropping the codesign and dsymutil phase.

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/TestValueObjPassByRef.py

16

lldbutil has a helper for running to a breakpoint by name.

[shafik]

lldb/source/Core/ValueObjectChild.cpp

202–205

lldb_private::DumpDataExtractor(…) is general purpose and it used by a lot of other code, it does know the value comes from a Scalar or otherwise it is just receiving a DataExtractor and obtaining the data from there.

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/Makefile

3

I did try using Specifying Registers for Local Variables and it did not work :-(

but in good news, I don't need the -O1 it was left over when I was struggling to get the test going.

3

Yes, this was left over when I was experimenting trying to get the test to work I do not need the -O1.

9

Let me see if I can remove the .o step.

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/TestValueObjPassByRef.py

11

Yes.

16

I could not get it to work using lldbutil I was working w/ @JDevlieghere on this and he thought that made sense. IIUC I would have rewrite the assembly file to make it work.

[shafik]

Removing use of -O1 from Makefile.

[shafik]

• Refactored the Makefile and test based on offline comments from Adrian.

[friss]

lldb/source/Core/ValueObjectChild.cpp

202–205

You didn't answer the most important question. Will GetValueAsUnsigned return the correct value on such a ValueObject once you remove this code?

[shafik]

lldb/source/Core/ValueObjectChild.cpp

202–205

apologies, misunderstood.

Yes, it does:

(lldb) script var = lldb.frame.FindVariable("u")
(lldb) script print(var.GetChildMemberWithName('raw'))
(uint32_t) raw = 1688469761
(lldb) script print(var.GetChildMemberWithName('a'))
(uint32_t:8) a = 1
(lldb) script print(var.GetChildMemberWithName('b'))
(uint32_t:8) b = 1
(lldb) script print(var.GetChildMemberWithName('c'))
(uint32_t:6) c = 36
(lldb) script print(var.GetChildMemberWithName('d'))
(uint32_t:2) d = 2
(lldb) script print(var.GetChildMemberWithName('e'))
(uint32_t:6) e = 36
(lldb) script print(var.GetChildMemberWithName('f'))
(uint32_t:2) f = 1

[shafik]

lldb/source/Core/ValueObjectChild.cpp

202–205

Whoops, copy-pasta:

(lldb) script print(var.GetChildMemberWithName('raw').GetValueAsUnsigned())
1688469761
(lldb) script print(var.GetChildMemberWithName('a').GetValueAsUnsigned())
1
(lldb) script print(var.GetChildMemberWithName('b').GetValueAsUnsigned())
1
(lldb) script print(var.GetChildMemberWithName('c').GetValueAsUnsigned())
36
(lldb) script print(var.GetChildMemberWithName('d').GetValueAsUnsigned())
2
(lldb) script print(var.GetChildMemberWithName('e').GetValueAsUnsigned())
36
(lldb) script print(var.GetChildMemberWithName('f').GetValueAsUnsigned())
1

[shafik]

• Add more tests

[aprantl]

The test LGTM now! Please be sure to address Fred's comment before committing.

[aprantl]

Do we have an end-to-end (with source code instead of assembler) test for ObjC bitfields, too? If not, it might still be a good a idea to add one even if it doesn't add coverage for this particular change.

[teemperor]

I just have a small comment about the test. If you build the test with an llvm.org version of clang (best if it contains the git hash it was build from) and you don't include headers (they don't seem to be required for the test), then the file would be much easier to update/extend for other people.

[shafik]

Updated to use llvm.org clang, remove header files from the main.c and add the commit hash for the clang so that it is easier to replicate the main.s in the future.

[labath]

This manifested itself for variables in registers because those end up being described as eValueTypeScalar, is that so?

If that's the case, then I think this would also manifest for variables described via DW_OP_constu 0xdead, DW_OP_stack_value. And if *that* is true, then this could be tested a lot simpler by having a global variable described by DW_OP_stack_value and "target variable"-ing it -- no makefiles, no python, just a simple .s file. And it would run on all platforms, not just darwin.

test/Shell/SymbolFile/DWARF/DW_OP_piece-struct.s tests a very similar thing in precisely this way. I suspect you could just take that test as a template and replace the struct definition with one that contains bitfieds.

[shafik]

In D85376#2209638, @labath wrote:

This manifested itself for variables in registers because those end up being described as eValueTypeScalar, is that so?

If that's the case, then I think this would also manifest for variables described via DW_OP_constu 0xdead, DW_OP_stack_value. And if *that* is true, then this could be tested a lot simpler by having a global variable described by DW_OP_stack_value and "target variable"-ing it -- no makefiles, no python, just a simple .s file. And it would run on all platforms, not just darwin.

test/Shell/SymbolFile/DWARF/DW_OP_piece-struct.s tests a very similar thing in precisely this way. I suspect you could just take that test as a template and replace the struct definition with one that contains bitfieds.

This sounds like a great approach, I have unfortunately been struggling to get a test case that works. It looks like I am hitting another bug, I am not surprised b/c using slight variations on this code I have found other three other bugs with how we deal with DW_OP_piece, DW_OP_bit_piece and I think DW_AT_const_value respectively.

I have been working w/ this:

#include <stdio.h>

typedef union
{
  unsigned raw;
  struct 
  {
    unsigned a : 8;
    unsigned b : 8;
    unsigned c : 6;
    unsigned d : 2;
    unsigned e : 6;
    unsigned f : 2;
  } ; 
} U;

static U ug= (U)(unsigned)0x0;

void f(U u) {
  printf( "%d\n", u.raw);
  return;
}

int main() {
  ug.raw = 0x64A40101;

  f(ug);
  printf( "%d\n", ug.raw);
}

and compiling as using clang -O1 -gdwarf-4 but we obtain bad values:

(lldb) target variable ug
(U) ug = {
  raw = 3395301392
   = (a = 16, b = 48, c = 32, d = 1, e = 10, f = 3)
}

I tried generating assembly and manually adjusting the debug info but I was not able to get very far there.

FYI this was the DWARF expression it was generating:

DW_AT_location	(DW_OP_addr 0x100002010, DW_OP_deref_size 0x1, DW_OP_constu 0x64a40101, DW_OP_mul, DW_OP_lit0, DW_OP_plus, DW_OP_stack_value)

If you can come up w/ a way to generate a test that produces correct values I am happy to use it!

[shafik]

We found a way to hand modify the assembly and it looks good, I just need to convert it to a test.

[shafik]

Replacing python test with Shell test

[teemperor]

I'll leave the test review to Pavel who knows that much better, but I have two last nits about the test.

lldb/test/Shell/SymbolFile/DWARF/valueobject-pass-by-reg.s

59 ↗

(On Diff #285176)

I think this was still generated with system clang. info_string below says this was compiled by Apple clang version 12.0.0 (clang-1200.0.31.1) and not the listed commit (which would create an info_string like clang version 12.0.0 (https://github.com/llvm/llvm-project 86dea1f39bd127776b999e10dff212003068d30a).)

149 ↗

(On Diff #285176)

You can avoid these system-specific paths by compiling the file in /tmp with your cwd in /tmp and passing -isysroot / to the clang invocation. This way this section would look like this for everyone independently of their system username or macOS version (which will make updating this much easier):

.asciz  "clang version 12.0.0 (https://github.com/llvm/llvm-project 6acb897dfbc0ec22007cde50b3bc9c60f4674fb2)" ## string offset=0
.asciz  "/tmp/weird.c"                  ## string offset=101                  
.asciz  "/"                             ## string offset=114                  
.asciz  "/tmp"                          ## string offset=116                  
.asciz  "ug"                            ## string offset=121                  
.asciz  "U"                             ## string offset=124                  
.asciz  "raw"                           ## string offset=126                  
.asciz  "unsigned int"                  ## string offset=130                  
.asciz  "a"                             ## string offset=143 

[friss]

lldb/test/Shell/SymbolFile/DWARF/valueobject-pass-by-reg.s

14–40 ↗

(On Diff #285176)

This gives a much more compact debug info section:

typedef union {
  unsigned raw;
  struct {
     unsigned a : 8;
     unsigned b : 8;
     unsigned c : 6;
     unsigned d : 2;
     unsigned e : 6;
     unsigned f : 2;
  };
} U;

// This appears first in the debug info and pulls the type definition in...
static U __attribute__((used)) _type_anchor;
// ... then our useful variable appears last in the debug info and we can
// tweak the assembly without needing to edit a lot of offsets by hand.
static U ug;

extern void f(U);

// Omit debug info for main.
__attribute__((nodebug))
int main() {
  ug.raw = 0x64A40101;
  f(ug);
  f((U)ug.raw);
}

You can easily edit out the TEXT section, the line table and the accelerator tables and patch the location expression to give you a minimal binary.

62–63 ↗

(On Diff #285176)

I don't think you need the TEXT segment at all, or at least you can make it empty.

[shafik]

Updated test using more compact code from Fred.

[labath]

This looks good to me. I appreciate the efforts taken to reduce the test size.

The trick for controlling the debug info order is neat, and I may end up using it some time. FWIW, the way I usually handle these things is by first replacing all constant debug info offsets with symbolic references (.long 123 -> .long .Lmytype-.debug_info). After that, it's possible to freely manipulate any debug info entry. (At that point I usually delete all DW_AT_decl_file/lines and other boring attributes, which tends to reduce the file a lot).

lldb/test/Shell/SymbolFile/DWARF/valueobject-pass-by-reg.s

1 ↗

(On Diff #285233)

I don't think the test file name matches what is being tested anymore. Maybe name it something like DW_AT_data_bit_offset-DW_OP_stack_value (in line with other tests in this folder)?

[shafik]

Update test name

lldb/source/Core/ValueObjectChild.cpp

if (parent->UpdateValueIfNeeded(false)) {
             }
           }
         } break;
 
         case Value::eValueTypeScalar:
           // try to extract the child value from the parent's scalar value
           {
             Scalar scalar(m_value.GetScalar());
-            if (m_bitfield_bit_size)
-              scalar.ExtractBitfield(m_bitfield_bit_size,
-                                     m_bitfield_bit_offset);
-            else
-              scalar.ExtractBitfield(8 * m_byte_size, 8 * m_byte_offset);
             m_value.GetScalar() = scalar;
           }
           break;
         default:
           m_error.SetErrorString("parent has invalid value.");
           break;
         }
       }

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/Makefile

+EXE := a.out
+
+include Makefile.rules
+
+$(EXE):
+  $(CC) $(SRCDIR)/main.s -c -o main.o
+  $(CC) main.o -o a.out

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/TestValueObjPassByRef.py

+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class TestValueObjPassByRef(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @skipUnlessDarwin
+    def test(self):
+        self.build()
+        self.runCmd("file " + self.getBuildArtifact("a.out"), CURRENT_EXECUTABLE_SET)
+        self.runCmd("b f");
+        self.runCmd("run");
+
+        self.expect("frame var -L", substrs = [ "rsi: (U) u = {",
+                      "scalar:   raw = 1688469761",
+                      "scalar:     a = 1",
+                      "scalar:     b = 1",
+                      "scalar:     c = 36",
+                      "scalar:     d = 2",
+                      "scalar:     e = 36",
+                      "scalar:     f = 1",
+                      "}",
+                      "}"])
+

lldb/test/API/functionalities/data-formatter/valueobj-pass-by-reg/main.s

+## This was generated from the following code:
+##
+## We are testing how ValueObject deals with bit-fields when an argument is
+## passed by register. Compiling at -O1 allows us to capture this case and
+## test it.
+##
+## #include <stdint.h>
+## #include <stdio.h>
+##
+## typedef union
+## {
+##  uint32_t raw;
+##  struct
+##  {
+##    uint32_t a : 8;
+##    uint32_t b : 8;
+##    uint32_t c : 6;
+##    uint32_t d : 2;
+##    uint32_t e : 6;
+##    uint32_t f : 2;
+##  } ;
+## } U;
+##
+## void f(U u) {
+##   printf( "%d\n", u.raw);
+##   return;
+## }
+##
+## int main() {
+##   U u;
+##   u.raw = 0x64A40101;
+##
+##   f(u);
+## }
+##
+## Compiled as follows:
+##
+##
+## clang -g -O1 main.c  -o main
+## clang -g -O1 main.c -S -o main.s
+##
+  .section  __TEXT,__text,regular,pure_instructions
+  .build_version macos, 10, 15  sdk_version 10, 15
+  .globl  _f                      ## -- Begin function f
+  .p2align  4, 0x90
+_f:                                     ## @f
+Lfunc_begin0:
+  .file 1 "/Users/shafik/code" "main.c"
+  .loc  1 18 0                  ## main.c:18:0
+  .cfi_startproc
+## %bb.0:
+  pushq %rbp
+  .cfi_def_cfa_offset 16
+  .cfi_offset %rbp, -16
+  movq  %rsp, %rbp
+  .cfi_def_cfa_register %rbp
+  ##DEBUG_VALUE: f:u <- $edi
+  movl  %edi, %esi
+Ltmp0:
+  ##DEBUG_VALUE: f:u <- $esi
+  .loc  1 19 3 prologue_end     ## main.c:19:3
+  leaq  L_.str(%rip), %rdi
+  ##DEBUG_VALUE: f:u <- $esi
+  xorl  %eax, %eax
+  popq  %rbp
+  jmp _printf                 ## TAILCALL
+Ltmp1:
+Lfunc_end0:
+  .cfi_endproc
+                                        ## -- End function
+  .globl  _main                   ## -- Begin function main
+  .p2align  4, 0x90
+_main:                                  ## @main
+Lfunc_begin1:
+  .loc  1 23 0                  ## main.c:23:0
+  .cfi_startproc
+## %bb.0:
+  pushq %rbp
+  .cfi_def_cfa_offset 16
+  .cfi_offset %rbp, -16
+  movq  %rsp, %rbp
+  .cfi_def_cfa_register %rbp
+Ltmp2:
+  ##DEBUG_VALUE: main:u <- 1688469761
+  .loc  1 27 3 prologue_end     ## main.c:27:3
+  movl  $1688469761, %edi       ## imm = 0x64A40101
+  callq _f
+Ltmp3:
+  .loc  1 28 1                  ## main.c:28:1
+  xorl  %eax, %eax
+  popq  %rbp
+  retq
+Ltmp4:
+Lfunc_end1:
+  .cfi_endproc
+                                        ## -- End function
+  .section  __TEXT,__cstring,cstring_literals
+L_.str:                                 ## @.str
+  .asciz  "%d\n"
+
+  .file  2 "/Applications/Xcode5.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/usr/include/_types" "_uint32_t.h"
+  .section  __DWARF,__debug_str,regular,debug
+Linfo_string:
+  .asciz  "Apple clang version 11.0.0 (clang-1100.0.31.5)" ## string offset=0
+  .asciz  "main.c"                ## string offset=47
+  .asciz  "/Users/shafik/code"    ## string offset=54
+  .asciz  "f"                     ## string offset=73
+  .asciz  "main"                  ## string offset=75
+  .asciz  "int"                   ## string offset=80
+  .asciz  "u"                     ## string offset=84
+  .asciz  "U"                     ## string offset=86
+  .asciz  "raw"                   ## string offset=88
+  .asciz  "uint32_t"              ## string offset=92
+  .asciz  "unsigned int"          ## string offset=101
+  .asciz  "a"                     ## string offset=114
+  .asciz  "b"                     ## string offset=116
+  .asciz  "c"                     ## string offset=118
+  .asciz  "d"                     ## string offset=120
+  .asciz  "e"                     ## string offset=122
+  .section  __DWARF,__debug_loc,regular,debug
+Lsection_debug_loc:
+Ldebug_loc0:
+.set Lset0, Lfunc_begin0-Lfunc_begin0
+  .quad Lset0
+.set Lset1, Ltmp0-Lfunc_begin0
+  .quad Lset1
+  .short  1                       ## Loc expr size
+  .byte 85                      ## super-register DW_OP_reg5
+.set Lset2, Ltmp0-Lfunc_begin0
+  .quad Lset2
+.set Lset3, Ltmp1-Lfunc_begin0
+  .quad Lset3
+  .short  1                       ## Loc expr size
+  .byte 84                      ## super-register DW_OP_reg4
+  .quad 0
+  .quad 0
+  .section  __DWARF,__debug_abbrev,regular,debug
+Lsection_abbrev:
+  .byte 1                       ## Abbreviation Code
+  .byte 17                      ## DW_TAG_compile_unit
+  .byte 1                       ## DW_CHILDREN_yes
+  .byte 37                      ## DW_AT_producer
+  .byte 14                      ## DW_FORM_strp
+  .byte 19                      ## DW_AT_language
+  .byte 5                       ## DW_FORM_data2
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 16                      ## DW_AT_stmt_list
+  .byte 23                      ## DW_FORM_sec_offset
+  .byte 27                      ## DW_AT_comp_dir
+  .byte 14                      ## DW_FORM_strp
+  .ascii  "\264B"                 ## DW_AT_GNU_pubnames
+  .byte 25                      ## DW_FORM_flag_present
+  .ascii  "\341\177"              ## DW_AT_APPLE_optimized
+  .byte 25                      ## DW_FORM_flag_present
+  .byte 17                      ## DW_AT_low_pc
+  .byte 1                       ## DW_FORM_addr
+  .byte 18                      ## DW_AT_high_pc
+  .byte 6                       ## DW_FORM_data4
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 2                       ## Abbreviation Code
+  .byte 46                      ## DW_TAG_subprogram
+  .byte 1                       ## DW_CHILDREN_yes
+  .byte 17                      ## DW_AT_low_pc
+  .byte 1                       ## DW_FORM_addr
+  .byte 18                      ## DW_AT_high_pc
+  .byte 6                       ## DW_FORM_data4
+  .byte 64                      ## DW_AT_frame_base
+  .byte 24                      ## DW_FORM_exprloc
+  .byte 122                     ## DW_AT_call_all_calls
+  .byte 25                      ## DW_FORM_flag_present
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 39                      ## DW_AT_prototyped
+  .byte 25                      ## DW_FORM_flag_present
+  .byte 63                      ## DW_AT_external
+  .byte 25                      ## DW_FORM_flag_present
+  .ascii  "\341\177"              ## DW_AT_APPLE_optimized
+  .byte 25                      ## DW_FORM_flag_present
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 3                       ## Abbreviation Code
+  .byte 5                       ## DW_TAG_formal_parameter
+  .byte 0                       ## DW_CHILDREN_no
+  .byte 2                       ## DW_AT_location
+  .byte 23                      ## DW_FORM_sec_offset
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 73                      ## DW_AT_type
+  .byte 19                      ## DW_FORM_ref4
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 4                       ## Abbreviation Code
+  .byte 46                      ## DW_TAG_subprogram
+  .byte 1                       ## DW_CHILDREN_yes
+  .byte 17                      ## DW_AT_low_pc
+  .byte 1                       ## DW_FORM_addr
+  .byte 18                      ## DW_AT_high_pc
+  .byte 6                       ## DW_FORM_data4
+  .byte 64                      ## DW_AT_frame_base
+  .byte 24                      ## DW_FORM_exprloc
+  .byte 122                     ## DW_AT_call_all_calls
+  .byte 25                      ## DW_FORM_flag_present
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 73                      ## DW_AT_type
+  .byte 19                      ## DW_FORM_ref4
+  .byte 63                      ## DW_AT_external
+  .byte 25                      ## DW_FORM_flag_present
+  .ascii  "\341\177"              ## DW_AT_APPLE_optimized
+  .byte 25                      ## DW_FORM_flag_present
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 5                       ## Abbreviation Code
+  .byte 52                      ## DW_TAG_variable
+  .byte 0                       ## DW_CHILDREN_no
+  .byte 28                      ## DW_AT_const_value
+  .byte 15                      ## DW_FORM_udata
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 73                      ## DW_AT_type
+  .byte 19                      ## DW_FORM_ref4
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 6                       ## Abbreviation Code
+  .byte 72                      ## DW_TAG_call_site
+  .byte 0                       ## DW_CHILDREN_no
+  .byte 127                     ## DW_AT_call_origin
+  .byte 19                      ## DW_FORM_ref4
+  .byte 125                     ## DW_AT_call_return_pc
+  .byte 1                       ## DW_FORM_addr
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 7                       ## Abbreviation Code
+  .byte 36                      ## DW_TAG_base_type
+  .byte 0                       ## DW_CHILDREN_no
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 62                      ## DW_AT_encoding
+  .byte 11                      ## DW_FORM_data1
+  .byte 11                      ## DW_AT_byte_size
+  .byte 11                      ## DW_FORM_data1
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 8                       ## Abbreviation Code
+  .byte 22                      ## DW_TAG_typedef
+  .byte 0                       ## DW_CHILDREN_no
+  .byte 73                      ## DW_AT_type
+  .byte 19                      ## DW_FORM_ref4
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 9                       ## Abbreviation Code
+  .byte 23                      ## DW_TAG_union_type
+  .byte 1                       ## DW_CHILDREN_yes
+  .byte 11                      ## DW_AT_byte_size
+  .byte 11                      ## DW_FORM_data1
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 10                      ## Abbreviation Code
+  .byte 13                      ## DW_TAG_member
+  .byte 0                       ## DW_CHILDREN_no
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 73                      ## DW_AT_type
+  .byte 19                      ## DW_FORM_ref4
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 56                      ## DW_AT_data_member_location
+  .byte 11                      ## DW_FORM_data1
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 11                      ## Abbreviation Code
+  .byte 13                      ## DW_TAG_member
+  .byte 0                       ## DW_CHILDREN_no
+  .byte 73                      ## DW_AT_type
+  .byte 19                      ## DW_FORM_ref4
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 56                      ## DW_AT_data_member_location
+  .byte 11                      ## DW_FORM_data1
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 12                      ## Abbreviation Code
+  .byte 19                      ## DW_TAG_structure_type
+  .byte 1                       ## DW_CHILDREN_yes
+  .byte 11                      ## DW_AT_byte_size
+  .byte 11                      ## DW_FORM_data1
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 13                      ## Abbreviation Code
+  .byte 13                      ## DW_TAG_member
+  .byte 0                       ## DW_CHILDREN_no
+  .byte 3                       ## DW_AT_name
+  .byte 14                      ## DW_FORM_strp
+  .byte 73                      ## DW_AT_type
+  .byte 19                      ## DW_FORM_ref4
+  .byte 58                      ## DW_AT_decl_file
+  .byte 11                      ## DW_FORM_data1
+  .byte 59                      ## DW_AT_decl_line
+  .byte 11                      ## DW_FORM_data1
+  .byte 13                      ## DW_AT_bit_size
+  .byte 11                      ## DW_FORM_data1
+  .byte 107                     ## DW_AT_data_bit_offset
+  .byte 11                      ## DW_FORM_data1
+  .byte 0                       ## EOM(1)
+  .byte 0                       ## EOM(2)
+  .byte 0                       ## EOM(3)
+  .section  __DWARF,__debug_info,regular,debug
+Lsection_info:
+Lcu_begin0:
+.set Lset4, Ldebug_info_end0-Ldebug_info_start0 ## Length of Unit
+  .long Lset4
+Ldebug_info_start0:
+  .short  4                       ## DWARF version number
+.set Lset5, Lsection_abbrev-Lsection_abbrev ## Offset Into Abbrev. Section
+  .long Lset5
+  .byte 8                       ## Address Size (in bytes)
+  .byte 1                       ## Abbrev [1] 0xb:0x10c DW_TAG_compile_unit
+  .long 0                       ## DW_AT_producer
+  .short  12                      ## DW_AT_language
+  .long 47                      ## DW_AT_name
+.set Lset6, Lline_table_start0-Lsection_line ## DW_AT_stmt_list
+  .long Lset6
+  .long 54                      ## DW_AT_comp_dir
+                                        ## DW_AT_GNU_pubnames
+                                        ## DW_AT_APPLE_optimized
+  .quad Lfunc_begin0            ## DW_AT_low_pc
+.set Lset7, Lfunc_end1-Lfunc_begin0     ## DW_AT_high_pc
+  .long Lset7
+  .byte 2                       ## Abbrev [2] 0x2a:0x25 DW_TAG_subprogram
+  .quad Lfunc_begin0            ## DW_AT_low_pc
+.set Lset8, Lfunc_end0-Lfunc_begin0     ## DW_AT_high_pc
+  .long Lset8
+  .byte 1                       ## DW_AT_frame_base
+  .byte 86
+                                        ## DW_AT_call_all_calls
+  .long 73                      ## DW_AT_name
+  .byte 1                       ## DW_AT_decl_file
+  .byte 18                      ## DW_AT_decl_line
+                                        ## DW_AT_prototyped
+                                        ## DW_AT_external
+                                        ## DW_AT_APPLE_optimized
+  .byte 3                       ## Abbrev [3] 0x3f:0xf DW_TAG_formal_parameter
+.set Lset9, Ldebug_loc0-Lsection_debug_loc ## DW_AT_location
+  .long Lset9
+  .long 84                      ## DW_AT_name
+  .byte 1                       ## DW_AT_decl_file
+  .byte 18                      ## DW_AT_decl_line
+  .long 141                     ## DW_AT_type
+  .byte 0                       ## End Of Children Mark
+  .byte 4                       ## Abbrev [4] 0x4f:0x37 DW_TAG_subprogram
+  .quad Lfunc_begin1            ## DW_AT_low_pc
+.set Lset10, Lfunc_end1-Lfunc_begin1    ## DW_AT_high_pc
+  .long Lset10
+  .byte 1                       ## DW_AT_frame_base
+  .byte 86
+                                        ## DW_AT_call_all_calls
+  .long 75                      ## DW_AT_name
+  .byte 1                       ## DW_AT_decl_file
+  .byte 23                      ## DW_AT_decl_line
+  .long 134                     ## DW_AT_type
+                                        ## DW_AT_external
+                                        ## DW_AT_APPLE_optimized
+  .byte 5                       ## Abbrev [5] 0x68:0x10 DW_TAG_variable
+  .ascii  "\201\202\220\245\006"  ## DW_AT_const_value
+  .long 84                      ## DW_AT_name
+  .byte 1                       ## DW_AT_decl_file
+  .byte 24                      ## DW_AT_decl_line
+  .long 141                     ## DW_AT_type
+  .byte 6                       ## Abbrev [6] 0x78:0xd DW_TAG_call_site
+  .long 42                      ## DW_AT_call_origin
+  .quad Ltmp3-Lfunc_begin1      ## DW_AT_call_return_pc
+  .byte 0                       ## End Of Children Mark
+  .byte 7                       ## Abbrev [7] 0x86:0x7 DW_TAG_base_type
+  .long 80                      ## DW_AT_name
+  .byte 5                       ## DW_AT_encoding
+  .byte 4                       ## DW_AT_byte_size
+  .byte 8                       ## Abbrev [8] 0x8d:0xb DW_TAG_typedef
+  .long 152                     ## DW_AT_type
+  .long 86                      ## DW_AT_name
+  .byte 1                       ## DW_AT_decl_file
+  .byte 16                      ## DW_AT_decl_line
+  .byte 9                       ## Abbrev [9] 0x98:0x6c DW_TAG_union_type
+  .byte 4                       ## DW_AT_byte_size
+  .byte 1                       ## DW_AT_decl_file
+  .byte 4                       ## DW_AT_decl_line
+  .byte 10                      ## Abbrev [10] 0x9c:0xc DW_TAG_member
+  .long 88                      ## DW_AT_name
+  .long 260                     ## DW_AT_type
+  .byte 1                       ## DW_AT_decl_file
+  .byte 6                       ## DW_AT_decl_line
+  .byte 0                       ## DW_AT_data_member_location
+  .byte 11                      ## Abbrev [11] 0xa8:0x8 DW_TAG_member
+  .long 176                     ## DW_AT_type
+  .byte 1                       ## DW_AT_decl_file
+  .byte 7                       ## DW_AT_decl_line
+  .byte 0                       ## DW_AT_data_member_location
+  .byte 12                      ## Abbrev [12] 0xb0:0x53 DW_TAG_structure_type
+  .byte 4                       ## DW_AT_byte_size
+  .byte 1                       ## DW_AT_decl_file
+  .byte 7                       ## DW_AT_decl_line
+  .byte 13                      ## Abbrev [13] 0xb4:0xd DW_TAG_member
+  .long 114                     ## DW_AT_name
+  .long 260                     ## DW_AT_type
+  .byte 1                       ## DW_AT_decl_file
+  .byte 9                       ## DW_AT_decl_line
+  .byte 8                       ## DW_AT_bit_size
+  .byte 0                       ## DW_AT_data_bit_offset
+  .byte 13                      ## Abbrev [13] 0xc1:0xd DW_TAG_member
+  .long 116                     ## DW_AT_name
+  .long 260                     ## DW_AT_type
+  .byte 1                       ## DW_AT_decl_file
+  .byte 10                      ## DW_AT_decl_line
+  .byte 8                       ## DW_AT_bit_size
+  .byte 8                       ## DW_AT_data_bit_offset
+  .byte 13                      ## Abbrev [13] 0xce:0xd DW_TAG_member
+  .long 118                     ## DW_AT_name
+  .long 260                     ## DW_AT_type
+  .byte 1                       ## DW_AT_decl_file
+  .byte 11                      ## DW_AT_decl_line
+  .byte 6                       ## DW_AT_bit_size
+  .byte 16                      ## DW_AT_data_bit_offset
+  .byte 13                      ## Abbrev [13] 0xdb:0xd DW_TAG_member
+  .long 120                     ## DW_AT_name
+  .long 260                     ## DW_AT_type
+  .byte 1                       ## DW_AT_decl_file
+  .byte 12                      ## DW_AT_decl_line
+  .byte 2                       ## DW_AT_bit_size
+  .byte 22                      ## DW_AT_data_bit_offset
+  .byte 13                      ## Abbrev [13] 0xe8:0xd DW_TAG_member
+  .long 122                     ## DW_AT_name
+  .long 260                     ## DW_AT_type
+  .byte 1                       ## DW_AT_decl_file
+  .byte 13                      ## DW_AT_decl_line
+  .byte 6                       ## DW_AT_bit_size
+  .byte 24                      ## DW_AT_data_bit_offset
+  .byte 13                      ## Abbrev [13] 0xf5:0xd DW_TAG_member
+  .long 73                      ## DW_AT_name
+  .long 260                     ## DW_AT_type
+  .byte 1                       ## DW_AT_decl_file
+  .byte 14                      ## DW_AT_decl_line
+  .byte 2                       ## DW_AT_bit_size
+  .byte 30                      ## DW_AT_data_bit_offset
+  .byte 0                       ## End Of Children Mark
+  .byte 0                       ## End Of Children Mark
+  .byte 8                       ## Abbrev [8] 0x104:0xb DW_TAG_typedef
+  .long 271                     ## DW_AT_type
+  .long 92                      ## DW_AT_name
+  .byte 2                       ## DW_AT_decl_file
+  .byte 31                      ## DW_AT_decl_line
+  .byte 7                       ## Abbrev [7] 0x10f:0x7 DW_TAG_base_type
+  .long 101                     ## DW_AT_name
+  .byte 7                       ## DW_AT_encoding
+  .byte 4                       ## DW_AT_byte_size
+  .byte 0                       ## End Of Children Mark
+Ldebug_info_end0:
+  .section  __DWARF,__debug_macinfo,regular,debug
+Ldebug_macinfo:
+  .byte 0                       ## End Of Macro List Mark
+  .section  __DWARF,__apple_names,regular,debug
+Lnames_begin:
+  .long 1212240712              ## Header Magic
+  .short  1                       ## Header Version
+  .short  0                       ## Header Hash Function
+  .long 2                       ## Header Bucket Count
+  .long 2                       ## Header Hash Count
+  .long 12                      ## Header Data Length
+  .long 0                       ## HeaderData Die Offset Base
+  .long 1                       ## HeaderData Atom Count
+  .short  1                       ## DW_ATOM_die_offset
+  .short  6                       ## DW_FORM_data4
+  .long 0                       ## Bucket 0
+  .long 1                       ## Bucket 1
+  .long 2090499946              ## Hash in Bucket 0
+  .long 177675                  ## Hash in Bucket 1
+.set Lset11, LNames0-Lnames_begin       ## Offset in Bucket 0
+  .long Lset11
+.set Lset12, LNames1-Lnames_begin       ## Offset in Bucket 1
+  .long Lset12
+LNames0:
+  .long 75                      ## main
+  .long 1                       ## Num DIEs
+  .long 79
+  .long 0
+LNames1:
+  .long 73                      ## f
+  .long 1                       ## Num DIEs
+  .long 42
+  .long 0
+  .section  __DWARF,__apple_objc,regular,debug
+Lobjc_begin:
+  .long 1212240712              ## Header Magic
+  .short  1                       ## Header Version
+  .short  0                       ## Header Hash Function
+  .long 1                       ## Header Bucket Count
+  .long 0                       ## Header Hash Count
+  .long 12                      ## Header Data Length
+  .long 0                       ## HeaderData Die Offset Base
+  .long 1                       ## HeaderData Atom Count
+  .short  1                       ## DW_ATOM_die_offset
+  .short  6                       ## DW_FORM_data4
+  .long -1                      ## Bucket 0
+  .section  __DWARF,__apple_namespac,regular,debug
+Lnamespac_begin:
+  .long 1212240712              ## Header Magic
+  .short  1                       ## Header Version
+  .short  0                       ## Header Hash Function
+  .long 1                       ## Header Bucket Count
+  .long 0                       ## Header Hash Count
+  .long 12                      ## Header Data Length
+  .long 0                       ## HeaderData Die Offset Base
+  .long 1                       ## HeaderData Atom Count
+  .short  1                       ## DW_ATOM_die_offset
+  .short  6                       ## DW_FORM_data4
+  .long -1                      ## Bucket 0
+  .section  __DWARF,__apple_types,regular,debug
+Ltypes_begin:
+  .long 1212240712              ## Header Magic
+  .short  1                       ## Header Version
+  .short  0                       ## Header Hash Function
+  .long 4                       ## Header Bucket Count
+  .long 4                       ## Header Hash Count
+  .long 20                      ## Header Data Length
+  .long 0                       ## HeaderData Die Offset Base
+  .long 3                       ## HeaderData Atom Count
+  .short  1                       ## DW_ATOM_die_offset
+  .short  6                       ## DW_FORM_data4
+  .short  3                       ## DW_ATOM_die_tag
+  .short  5                       ## DW_FORM_data2
+  .short  4                       ## DW_ATOM_type_flags
+  .short  11                      ## DW_FORM_data1
+  .long 0                       ## Bucket 0
+  .long 1                       ## Bucket 1
+  .long 3                       ## Bucket 2
+  .long -1                      ## Bucket 3
+  .long 193495088               ## Hash in Bucket 0
+  .long 290711645               ## Hash in Bucket 1
+  .long -1304652851             ## Hash in Bucket 1
+  .long 177658                  ## Hash in Bucket 2
+.set Lset13, Ltypes3-Ltypes_begin       ## Offset in Bucket 0
+  .long Lset13
+.set Lset14, Ltypes1-Ltypes_begin       ## Offset in Bucket 1
+  .long Lset14
+.set Lset15, Ltypes2-Ltypes_begin       ## Offset in Bucket 1
+  .long Lset15
+.set Lset16, Ltypes0-Ltypes_begin       ## Offset in Bucket 2
+  .long Lset16
+Ltypes3:
+  .long 80                      ## int
+  .long 1                       ## Num DIEs
+  .long 134
+  .short  36
+  .byte 0
+  .long 0
+Ltypes1:
+  .long 92                      ## uint32_t
+  .long 1                       ## Num DIEs
+  .long 260
+  .short  22
+  .byte 0
+  .long 0
+Ltypes2:
+  .long 101                     ## unsigned int
+  .long 1                       ## Num DIEs
+  .long 271
+  .short  36
+  .byte 0
+  .long 0
+Ltypes0:
+  .long 86                      ## U
+  .long 1                       ## Num DIEs
+  .long 141
+  .short  22
+  .byte 0
+  .long 0
+  .section  __DWARF,__debug_gnu_pubn,regular,debug
+.set Lset17, LpubNames_end0-LpubNames_begin0 ## Length of Public Names Info
+  .long Lset17
+LpubNames_begin0:
+  .short  2                       ## DWARF Version
+.set Lset18, Lcu_begin0-Lsection_info   ## Offset of Compilation Unit Info
+  .long Lset18
+  .long 279                     ## Compilation Unit Length
+  .long 79                      ## DIE offset
+  .byte 48                      ## Attributes: FUNCTION, EXTERNAL
+  .asciz  "main"                  ## External Name
+  .long 42                      ## DIE offset
+  .byte 48                      ## Attributes: FUNCTION, EXTERNAL
+  .asciz  "f"                     ## External Name
+  .long 0                       ## End Mark
+LpubNames_end0:
+  .section  __DWARF,__debug_gnu_pubt,regular,debug
+.set Lset19, LpubTypes_end0-LpubTypes_begin0 ## Length of Public Types Info
+  .long Lset19
+LpubTypes_begin0:
+  .short  2                       ## DWARF Version
+.set Lset20, Lcu_begin0-Lsection_info   ## Offset of Compilation Unit Info
+  .long Lset20
+  .long 279                     ## Compilation Unit Length
+  .long 141                     ## DIE offset
+  .byte 144                     ## Attributes: TYPE, STATIC
+  .asciz  "U"                     ## External Name
+  .long 260                     ## DIE offset
+  .byte 144                     ## Attributes: TYPE, STATIC
+  .asciz  "uint32_t"              ## External Name
+  .long 271                     ## DIE offset
+  .byte 144                     ## Attributes: TYPE, STATIC
+  .asciz  "unsigned int"          ## External Name
+  .long 134                     ## DIE offset
+  .byte 144                     ## Attributes: TYPE, STATIC
+  .asciz  "int"                   ## External Name
+  .long 0                       ## End Mark
+LpubTypes_end0:
+
+.subsections_via_symbols
+  .section  __DWARF,__debug_line,regular,debug
+Lsection_line:
+Lline_table_start0: