Re: [PATCH] Disassemble over end of line table sequence.

[Doug Evans <dje at google dot com>]

I wonder if now is a good time to discuss whether we want to keep the
"source-centric" disassembly.
Does anyone actually find the current way useful?
[i.e. display the disassembly with possibly non-contiguous pcs, sorted
by source line number instead]

On Thu, Jan 13, 2011 at 2:39 AM, Andrew Burgess <aburgess@broadcom.com> wrote:
> Ping!
>
> Could someone cast an eye over this please.
>
> Thanks,
>
> Andrew
>
>
> On 15/12/2010 14:23, Andrew Burgess wrote:
>>
>> Within gdb we use line number 0 to mark the end of a sequence within the
>> line number tables. When disassembling with source code we sort the
>> lines based on the line number. As a result if a request is made to
>> disassemble a range of addresses that includes an end of sequence marker
>> the disassemble command will give an error rather than any sensible
>> output.
>>
>> In the included test I request a disassembly for a range of addresses
>> that spans a function boundary, currently this will fail. With the fix
>> the disassembly I get back still does not quite cover the complete range
>> of addresses requested, I am treating this problem as a separate issue
>> to be fixed in a later patch, here I am only interested in ordering the
>> lines correctly so that I get something sensible back rather than an
>> error.
>>
>> Thanks,
>>
>> Andrew
>>
>>
>>
>> gdb/
>>
>> 2010-12-10 ?Andrew Burgess<aburgess@broadcom.com>
>>
>> ? ? ? ? ? ?* (compare_lines): Sort by pc for entries where the line
>> ? ? ? ? ? ? ?number is 0, these are the end of sequence markers.
>>
>> gdb/testsuite/
>>
>> 2010-12-10 ?Andrew Burgess<aburgess@broadcom.com>
>>
>> ? ? ? ? ? ?* gdb.disasm/disasm-end-cu-1.c, gdb.disasm/disasm-end-cu-2.c,
>> ? ? ? ? ? ? ?gdb.disasm/disasm-end-cu.exp: New test for disassembling
>> ? ? ? ? ? ? ?over the boundary between two compilation units.
>>
>>
>> diff --git a/gdb/disasm.c b/gdb/disasm.c
>> index 9fa34a0..2259f3e 100644
>> --- a/gdb/disasm.c
>> +++ b/gdb/disasm.c
>> @@ -77,12 +77,22 @@ compare_lines (const void *mle1p, const void *mle2p)
>> ? ? mle1 = (struct dis_line_entry *) mle1p;
>> ? ? mle2 = (struct dis_line_entry *) mle2p;
>>
>> - ?val = mle1->line - mle2->line;
>> -
>> - ?if (val != 0)
>> - ? ?return val;
>> + ?/* Work with end of sequence markers
>> + ? ? where the line number is set to 0 */
>> + ?if ( mle1->line == 0 || mle2->line == 0 )
>> + ? ?{
>> + ? ? ?val = mle1->start_pc - mle2->start_pc;
>> + ? ? ?if ( val == 0 )
>> + ? ? ? ?val = mle1->line - mle2->line;
>> + ? ?}
>> + ?else
>> + ? ?{
>> + ? ? ?val = mle1->line - mle2->line;
>> + ? ? ?if (val == 0)
>> + ? ? ? ?val = mle1->start_pc - mle2->start_pc;
>> + ? ?}
>>
>> - ?return mle1->start_pc - mle2->start_pc;
>> + ?return val;
>> ? }
>>
>> ? static int
>> diff --git a/gdb/testsuite/gdb.disasm/disasm-end-cu-1.c
>> b/gdb/testsuite/gdb.disasm/disasm-end-cu-1.c
>> new file mode 100644
>> index 0000000..c031778
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.disasm/disasm-end-cu-1.c
>> @@ -0,0 +1,14 @@
>> +#include<stdio.h>
>> +
>> +void
>> +dummy_1 ()
>> +{
>> + ?printf("In dummy_1 ()\n");
>> +}
>> +
>> +int
>> +main ()
>> +{
>> + ?printf("Hello World!\n");
>> + ?return 0;
>> +}
>> diff --git a/gdb/testsuite/gdb.disasm/disasm-end-cu-2.c
>> b/gdb/testsuite/gdb.disasm/disasm-end-cu-2.c
>> new file mode 100644
>> index 0000000..7fddb87
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.disasm/disasm-end-cu-2.c
>> @@ -0,0 +1,13 @@
>> +#include<stdio.h>
>> +
>> +void
>> +dummy_2 ()
>> +{
>> + ?printf("In dummy_2 ()\n");
>> +}
>> +
>> +void
>> +dummy_3 ()
>> +{
>> + ?printf("In dummy_3 ()\n");
>> +}
>> diff --git a/gdb/testsuite/gdb.disasm/disasm-end-cu.exp
>> b/gdb/testsuite/gdb.disasm/disasm-end-cu.exp
>> new file mode 100644
>> index 0000000..fdbd179
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.disasm/disasm-end-cu.exp
>> @@ -0,0 +1,70 @@
>> +# Copyright 2010 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/>.
>> +
>> +# This test can only be run on targets which support DWARF-2 and use gas.
>> +# For now pick a sampling of likely targets.
>> +if {![istarget *-*-linux*]
>> +&& ?![istarget *-*-gnu*]
>> +&& ?![istarget *-*-elf*]
>> +&& ?![istarget *-*-openbsd*]
>> +&& ?![istarget arm-*-eabi*]
>> +&& ?![istarget powerpc-*-eabi*]} {
>> + ? ?return 0
>> +}
>> +
>> +# This test tries to disassemble over the boundary between two
>> compilation
>> +# units displaying source lines. This checks that the disassemble routine
>> +# can handle our use of line number 0 to mark the end of sequence.
>> +
>> +if { [prepare_for_testing disasm-end-cu.exp "disasm-end-cu"
>> {disasm-end-cu-1.c disasm-end-cu-2.c} {debug}] } {
>> + ? ?return -1
>> +}
>> +
>> +if ![runto_main] {
>> + ? ?return -1
>> +}
>> +
>> +set main_addr [get_hexadecimal_valueof "&main" "0"]
>> +set dummy_3_addr [get_hexadecimal_valueof "&dummy_3" "0"]
>> +
>> +if {$main_addr == 0 || $dummy_3_addr == 0 || $dummy_3_addr<= $main_addr}
>> {
>> + ? ?fail "Unable to extract required addresses, or addresses out of
>> order"
>> + ? ?return -1
>> +}
>> +
>> +send_gdb "disassemble /m ${main_addr},${dummy_3_addr}\n"
>> +gdb_expect {
>> + ? ?-re "Dump of assembler code from ${main_addr} to
>> ${dummy_3_addr}:\r\nEnd of assembler dump\." {
>> + ? ? ? ?fail "No output from the disassemble command"
>> + ? ?}
>> +
>> + ? ?-re "Line number 0 out of range;.* has $decimal lines\." {
>> + ? ? ? ?fail "The disassemble command failed"
>> + ? ?}
>> +
>> + ? ?-re "Dump of assembler code from ${main_addr} to
>> ${dummy_3_addr}:\r\n.*main.*End of assembler dump\." {
>> + ? ? ? ?pass "disassemble command returned some output"
>> + ? ?}
>> +
>> + ? ?-re ".*$gdb_prompt $" {
>> + ? ? ? ?fail "Unexpected output from disassemble command"
>> + ? ?}
>> +
>> + ? ?timeout {
>> + ? ? ? ?fail "(timeout) waiting for output of disassemble command"
>> + ? ?}
>> +}
>> +
>> +gdb_stop_suppressing_tests;
>>
>>
>>
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