Binutils with MCST patches
1aff717310
In the course of revising the test case for
gdb.dwarf2/dw2-ranges-func.exp, I added a new .c file which would
cause the "cold" range to be at a higher address than the rest of the
function. In these tests, the range in question isn't really cold in
the sense that a compiler has determined that it'll be executed less
frequently. Instead, it's simply the range that does not include the
entry pc. These tests are intended to mimic the output of such a
compiler, so I'll continue to refer to this range as "cold" in the
following discussion.
The original test case had only tested a cold range placed
at lower addresses than the rest of the function. During testing of the
new code where the cold range was placed at higher addresses, I found
that I could produce the following backtrace:
(gdb) bt
#0 0x0000000000401138 in baz ()
at dw2-ranges-func-hi-cold.c:72
#1 0x0000000000401131 in foo_cold ()
at dw2-ranges-func-hi-cold.c:64
#2 0x000000000040111e in foo ()
at dw2-ranges-func-hi-cold.c:50
#3 0x0000000000401144 in main ()
at dw2-ranges-func-hi-cold.c:78
This is correct, except that we'd like to see foo() listed instead
of foo_cold(). (I handle that problem in another patch.)
Now look at what happens for a similar backtrace where the cold range
is at a lower address than the foo's entry pc:
(gdb) bt
#0 0x000000000040110a in baz ()
at dw2-ranges-func-lo-cold.c:48
#1 0x0000000000401116 in foo ()
at dw2-ranges-func-lo-cold.c:54
#2 0x00007fffffffd4c0 in ?? ()
#3 0x0000000000401138 in foo ()
at dw2-ranges-func-lo-cold.c:70
Note that the backtrace doesn't go all the way back to main(). Moreover,
frame #2 is messed up.
I had seen this behavior when I had worked on the non-contiguous
address problem last year. At the time I convinced myself that the
mangled backtrace was "okay" since we're doing strange things with
the DWARF assembler. We're taking a function called foo_cold (though
it was originally called foo_low - my recent changes to the test case
changed the name) and via the magic of the DWARF assembler, we're
combining it into a separate (non-contiguous) range for foo. Thus,
it was a surprise to me when I got a good and complete backtrace when
the cold symbol is placed at an address that's greater than entry pc.
The function dwarf2_frame_cache (in dwarf2-frame.c) is making this
call:
if (get_frame_func_if_available (this_frame, &entry_pc)) ...
If that call succeeds (returns a true value), the FDE is then
processed up to the entry pc. It doesn't make sense to do this,
however, when the FDE in question does not contain the entry pc. This
can happen when the function in question is comprised of more than one
(non-contiguous) address range.
My fix is to add some comparisons to the test above to ensure that
ENTRY_PC is within the address range covered by the FDE.
gdb/ChangeLog:
* dwarf2-frame.c (dwarf2_frame_cache): Don't decode FDE instructions
for entry pc when entry pc is out of range for that FDE.
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README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.