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[Mingw-users] C++ dwarf2 output
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From: Dhaval O. <dha...@co...> - 2005-12-13 23:29:24
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Hello All:
I am having problems with DWARF2 debug information, so I am not sure
if my question belongs in here or in the GCC mailing list. I did a
search and came across problems with dwarf2 output that were fixed in
the 3.4.4 version. However, I built a cross-compiler for the MIPS
targets so I don't know if anyone else came across the problems which
I am seeing.
These are the following packages I am using:
gcc-core-3.4.4-20050522
gcc-g++-3.4.4-20050522
binutils-2.16.91-20050827
newlib-1.12.0
These are the compile time flags I am using -
CFLAGS = -g2 -mips2 -gdwarf-2 -fno-omit-frame-pointer -O0 -c -G 0 \
-$(ENDIAN) -D$(ENDIAN) -Wall -I. -I$(INCLUDE_DIR)
Once I built my elf-image I noticed that when using our in-house
debugger, some of the C++ files in my project had no debug source
line information associated with it. The globals information is fine.
I used read-elf to dump the DWARF2 debug information output for a
single object file. I had the following questions after going through
the DWARF2 output.
1) In the line number statements there are multiple "Extended opcode
1: End of Sequence" statments. I am not sure what this means even
after reading the spec? How do I differentiate between multiple "End
of Sequence" statments, that correspond to one DW_AT_stmt_list attribute?
2) In the line number statements there are multiple "Set File Name to
entry x in the File Name Table" entries. However, there is no
statement to set the File Name to the entry 1, which corresponds to
the source file that we are getting information for?
Is the DWARF output here incorrect or am I missing something here?
BTW I am not an expert:)
I am attaching parts of the output.
> readelf -W class.o
The section .debug_info contains:
Compilation Unit @ 0:
Length: 20172
Version: 2
Abbrev Offset: 0
Pointer Size: 4
<0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
DW_AT_stmt_list : 0
DW_AT_producer : GNU C++ 3.4.4 (mingw special) -g
DW_AT_language : 4 (C++)
DW_AT_name : Class.cpp
DW_AT_comp_dir : C:\dev\Test_mips
....
Dump of debug contents of section .debug_line:
Length: 1064
DWARF Version: 2
Prologue Length: 620
Minimum Instruction Length: 1
Initial value of 'is_stmt': 1
Line Base: -5
Line Range: 14
Opcode Base: 10
(Pointer size: 4)
Opcodes:
Opcode 1 has 0 args
Opcode 2 has 1 args
Opcode 3 has 1 args
Opcode 4 has 1 args
Opcode 5 has 1 args
Opcode 6 has 0 args
Opcode 7 has 0 args
Opcode 8 has 0 args
Opcode 9 has 1 args
The Directory Table:
c:/corelis/gnu/build/bin/../lib/gcc/mips-elf/3.4.4/../../../../include/c++/3.4.4
c:/corelis/gnu/build/bin/../lib/gcc/mips-elf/3.4.4/../../../../include/c++/3.4.4/bits
c:/corelis/gnu/build/bin/../lib/gcc/mips-elf/3.4.4/include
c:/corelis/gnu/build/bin/../lib/gcc/mips-elf/3.4.4/../../../../include/c++/3.4.4/ext
c:/corelis/gnu/build/bin/../lib/gcc/mips-elf/3.4.4/../../../../include/c++/3.4.4/mips-elf/bits
The File Name Table:
Entry Dir Time Size Name
1 0 0 0 Class.cpp
2 0 0 0 Class0.h
3 0 0 0 PtrTest.h
4 0 0 0 <internal>
5 1 0 0 new
6 1 0 0 exception
7 1 0 0 limits
8 2 0 0 basic_string.h
9 3 0 0 stddef.h
10 4 0 0 new_allocator.h
11 2 0 0 allocator.h
12 2 0 0 stringfwd.h
13 2 0 0 basic_string.tcc
14 5 0 0 atomic_word.h
Line Number Statements:
Set File Name to entry 2 in the File Name Table
Extended opcode 2: set Address to 0x0
Advance Line by 72 to 73
Copy
Special opcode 229: advance Address by 16 to 0x10 and Line by 0 to 73
Advance PC by 20 to 24
Extended opcode 1: End of Sequence
Set File Name to entry 3 in the File Name Table
Extended opcode 2: set Address to 0x0
Advance Line by 58 to 59
Copy
Advance PC by constant 17 to 0x11
Special opcode 103: advance Address by 7 to 0x18 and Line by 0 to 59
Advance PC by 44 to 44
Extended opcode 1: End of Sequence
Set File Name to entry 3 in the File Name Table
Extended opcode 2: set Address to 0x0
Advance Line by 62 to 63
Copy
Advance PC by constant 17 to 0x11
Special opcode 47: advance Address by 3 to 0x14 and Line by 0 to 63
Advance PC by 32 to 34
Extended opcode 1: End of Sequence
Set File Name to entry 3 in the File Name Table
Extended opcode 2: set Address to 0x0
Advance Line by 64 to 65
Copy
Advance PC by constant 17 to 0x11
Special opcode 47: advance Address by 3 to 0x14 and Line by 0 to 65
Advance PC by 32 to 34
Extended opcode 1: End of Sequence
Set File Name to entry 3 in the File Name Table
Extended opcode 2: set Address to 0x0
Advance Line by 66 to 67
Copy
Advance PC by constant 17 to 0x11
Special opcode 47: advance Address by 3 to 0x14 and Line by 0 to 67
Advance PC by 32 to 34
Extended opcode 1: End of Sequence
Set File Name to entry 3 in the File Name Table
Extended opcode 2: set Address to 0x0
Advance Line by 68 to 69
Copy
Advance PC by constant 17 to 0x11
Special opcode 47: advance Address by 3 to 0x14 and Line by 0 to 69
Advance PC by 44 to 40
Extended opcode 1: End of Sequence
....
Advance PC by 44 to b38
Special opcode 3: advance Address by 0 to 0xb38 and Line by -2 to 15
Advance Line by 44 to 59
Advance PC by 92 to b94
Copy
Advance PC by constant 17 to 0xba5
Special opcode 104: advance Address by 7 to 0xbac and Line by 1 to 60
Special opcode 229: advance Address by 16 to 0xbbc and Line by 0 to 60
Advance PC by 40 to be4
Special opcode 6: advance Address by 0 to 0xbe4 and Line by 1 to 61
Special opcode 229: advance Address by 16 to 0xbf4 and Line by 0 to 61
Advance PC by 40 to c1c
Extended opcode 1: End of Sequence
The section .debug_frame contains:
Thanks,
Dhaval |