Rob Lyerly via llvm-dev
2016-Apr-26 22:29 UTC
[llvm-dev] Generating debug information with OpenMP enabled
Hi all,
I'm compiling a C/OpenMP application with clang/LLVM v 3.7.1 on aarch64
("-target aarch64-linux-gnu"). I'm also compiling with
"-g" and
"-gdwarf-aranges" to get debugging information for my application.
For
most source code files (i.e. ones without OpenMP pragmas), the compiler
puts frame description entries (FDEs) in the ".debug_frame" section of
my
executable. The output from readelf looks pretty sane (in particular, the
address ranges look correct):
$ readelf --debug-dump=frames-interp <my bin>
Contents of the .debug_frame section:
00000000 0000000000000014 ffffffff CIE "" cf=1 df=-4 ra=30
LOC CFA
0000000000000000 r31+0
00000018 0000000000000024 00000000 FDE cie=00000000
*pc=0000000000410000..0000000000410238*
LOC CFA r19 r20 r21 r22 r29 ra
0000000000410000 r31+0 u u u u u u
0000000000410014 r29+16 c-24 c-32 c-40 c-48 c-16 c-8
...
However for the source code file with OpenMP pragmas, the compiler puts
frame descriptor entries in the ".eh_frame" section. I'm assuming
this is
because LLVM's OpenMP runtime is compiled using C++ and therefore needs
asynchronous unwind tables. Not a problem, but it's populating the address
ranges with (seemingly) bad values:
Contents of the .eh_frame section:
00000000 0000000000000014 00000000 CIE "zR" cf=1 df=-4 ra=30
LOC CFA
0000000000000000 r31+0
00000018 000000000000001c 0000001c FDE cie=00000000
*pc=ffffffffe0594070..ffffffffe05940ac*
LOC CFA r29 ra
ffffffffe0594070 r31+0 u u
ffffffffe059407c r29+16 c-16 c-8
...
Is this a bug, or are those address ranges correct? How am I supposed to
be interpreting those? Note that I don't have code anywhere near that
address range in my binary. Thanks!
--
Rob Lyerly
Graduate Research Assistant, Systems Software Research Group
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