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handle an unspecified return address column

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Debugging PR 16155 further, I found that the DWARF unwinder found the
function in question, but thought it had no registers saved
(fs->regs.num_regs == 0).

It seems to me that if a frame does not specify the return address
column, or if the return address column is explicitly marked as
DWARF2_FRAME_REG_UNSPECIFIED, then we should set the
"undefined_retaddr" flag and let the DWARF unwinder gracefully stop.

This patch implements that idea.

With this patch the backtrace works properly:

    (gdb) bt
    #0  0x0000007fb7ed485c in nanosleep () from /lib64/libc.so.6
    #1  0x0000007fb7ed4508 in sleep () from /lib64/libc.so.6
    #2  0x00000000004008bc in thread_function (arg=0x4) at threadapply.c:73
    #3  0x0000007fb7fad950 in start_thread () from /lib64/libpthread.so.0
    #4  0x0000007fb7f0956c in clone () from /lib64/libc.so.6

2013-11-22  Tom Tromey  <tromey@redhat.com>

	PR backtrace/16155:
	* dwarf2-frame.c (dwarf2_frame_cache): Set undefined_retaddr if
	the return address column is unspecified.

2013-11-22  Tom Tromey  <tromey@redhat.com>

	* gdb.dwarf2/dw2-bad-cfi.c: New file.
	* gdb.dwarf2/dw2-bad-cfi.exp: New file.
	* gdb.dwarf2/dw2-bad-cfi.S: New file.
This commit is contained in:
Tom Tromey
2013-11-13 11:10:55 -07:00
parent 6eeee81c8e
commit da2b2fdf57
6 changed files with 302 additions and 0 deletions
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4
gdb/dwarf2-frame.c
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@@ -1245,6 +1245,10 @@ incomplete CFI data; unspecified registers (e.g., %s) at %s"),
if (fs->retaddr_column < fs->regs.num_regs
&& fs->regs.reg[fs->retaddr_column].how == DWARF2_FRAME_REG_UNDEFINED)
cache->undefined_retaddr = 1;
else if (fs->retaddr_column >= fs->regs.num_regs
|| (fs->regs.reg[fs->retaddr_column].how
== DWARF2_FRAME_REG_UNSPECIFIED))
cache->undefined_retaddr = 1;
do_cleanups (old_chain);
discard_cleanups (reset_cache_cleanup);