4b2dfa9d87
Use the last endianness explicitly selected, either by choosing a binary
file or with the `set endian' command, for future automatic selection.
As observed with the `gdb.base/step-over-no-symbols.exp' test case when
discarding the binary file even while connected to a live target the
endianness automatically selected is reset to the GDB target's default,
even if it does not match the endianness of the target being talked to.
For example with a little-endian MIPS target and the default endianness
being big we get this:
(gdb) file .../gdb/testsuite/outputs/gdb.base/step-over-no-symbols/step-over-no-symbols
Reading symbols from .../gdb/testsuite/outputs/gdb.base/step-over-no-symbols/step-over-no-symbols...done.
(gdb) delete breakpoints
(gdb) info breakpoints
No breakpoints or watchpoints.
(gdb) break main
Breakpoint 1 at 0x400840: file .../gdb/testsuite/gdb.base/start.c, line 34.
[...]
(gdb) continue
Continuing.
Breakpoint 1, main () at .../gdb/testsuite/gdb.base/start.c:34
34 foo();
(gdb) delete breakpoints
Delete all breakpoints? (y or n) y
(gdb) info breakpoints
No breakpoints or watchpoints.
(gdb) file
A program is being debugged already.
Are you sure you want to change the file? (y or n) y
No executable file now.
Discard symbol table from `.../gdb/testsuite/outputs/gdb.base/step-over-no-symbols/step-over-no-symbols'? (y or n) y
No symbol file now.
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: purging symbols
p /x $pc
$1 = 0x40084000
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: get before PC
break *$pc
Breakpoint 2 at 0x40084000
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: break *$pc
set displaced-stepping off
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: set displaced-stepping off
stepi
Warning:
Cannot insert breakpoint 2.
Cannot access memory at address 0x40084000
Command aborted.
(gdb) FAIL: gdb.base/step-over-no-symbols.exp: displaced=off: stepi
p /x $pc
$2 = 0x40084000
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: get after PC
FAIL: gdb.base/step-over-no-symbols.exp: displaced=off: advanced
Remote debugging from host ...
monitor exit
(gdb) Killing process(es): ...
testcase .../gdb/testsuite/gdb.base/step-over-no-symbols.exp completed in 2 seconds
which shows that with the removal of the executable debugged the
endianness of $pc still at `main' gets swapped and the value in that
register is now incorrectly interpreted as 0x40084000 rather than
0x400840 as shown earlier on with the `break' command. Consequently the
debug session no longer works as expected, until the endianness is
overridden with an explicit `set endian little' command.
This will happen while working with any target hardware whose endianness
does not match the default GDB target's endianness guessed and recorded
for a later use in `initialize_current_architecture'.
Given that within a single run of GDB it is more likely that consecutive
target connections will use the same endianness than that the endianness
will be swapped between connections, it makes sense to preserve the last
endianness explicitly selected as the automatic default. It will make a
session like above, where an executable is removed, work correctly and
will retain the endianness for a further reconnection to the target.
And the new automatic default will still be overridden by subsequently
choosing a binary to debug, or with an explicit `set endian' command.
With the change in place the test case above completes successfully:
(gdb) continue
Continuing.
Breakpoint 1, main () at .../gdb/testsuite/gdb.base/start.c:34
34 foo();
(gdb) delete breakpoints
Delete all breakpoints? (y or n) y
(gdb) info breakpoints
No breakpoints or watchpoints.
(gdb) file
A program is being debugged already.
Are you sure you want to change the file? (y or n) y
No executable file now.
Discard symbol table from `.../gdb/testsuite/outputs/gdb.base/step-over-no-symbols/step-over-no-symbols'? (y or n) y
No symbol file now.
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: purging symbols
p /x $pc
warning: GDB can't find the start of the function at 0x400840.
GDB is unable to find the start of the function at 0x400840
and thus can't determine the size of that function's stack frame.
This means that GDB may be unable to access that stack frame, or
the frames below it.
This problem is most likely caused by an invalid program counter or
stack pointer.
However, if you think GDB should simply search farther back
from 0x400840 for code which looks like the beginning of a
function, you can increase the range of the search using the `set
heuristic-fence-post' command.
$1 = 0x400840
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: get before PC
break *$pc
Breakpoint 2 at 0x400840
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: break *$pc
set displaced-stepping off
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: set displaced-stepping off
stepi
warning: GDB can't find the start of the function at 0x4007f8.
0x004007f8 in ?? ()
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: stepi
p /x $pc
$2 = 0x4007f8
(gdb) PASS: gdb.base/step-over-no-symbols.exp: displaced=off: get after PC
PASS: gdb.base/step-over-no-symbols.exp: displaced=off: advanced
Remote debugging from host ...
monitor exit
(gdb) Killing process(es): ...
testcase .../gdb/testsuite/gdb.base/step-over-no-symbols.exp completed in 2 seconds
gdb/
* arch-utils.c (gdbarch_info_fill): Set `default_byte_order' to
the endianness selected.
* NEWS: Document `set endian auto' mode operation update.
gdb/doc/
* gdb.texinfo (Choosing Target Byte Order): Document endianness
selection details with the `set endian auto' mode.
gdb/testsuite
* gdb.base/endian.exp: New test.
* gdb.base/endian.c: New test source.
22 lines
785 B
C
22 lines
785 B
C
/* This testcase is part of GDB, the GNU debugger.
|
|
|
|
Copyright (C) 2018 Free Software Foundation, Inc.
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>. */
|
|
|
|
int
|
|
main (void)
|
|
{
|
|
return 0;
|
|
}
|