[PATCH v2 4/5] Allow display of negative offsets in print_address_symbolic()
Kevin Buettner
kevinb@redhat.com
Tue Jul 30 16:47:00 GMT 2019
I somehow missed pushing this commit when I pushed the rest of the
series. It was strange though - that second hunk of the patch was in,
but the first was not. Moreover, I didn't see an actual commit in master.
Regardless, it should be in now.
Thanks to Tom de Vries for his help in finding this problem.
Kevin
On Wed, 3 Jul 2019 21:55:02 -0700
Kevin Buettner <kevinb@redhat.com> wrote:
> When examining addresses associated with blocks with non-contiguous
> address ranges, it's not uncommon to see large positive offsets which,
> for some address width, actually represent a smaller negative offset.
> Here's an example taken from the test case (using the
> dw2-ranges-func-lo-cold executable):
>
> (gdb) x/5i foo_cold
> 0x40110d <foo+4294967277>: push %rbp
> 0x40110e <foo+4294967278>: mov %rsp,%rbp
> 0x401111 <foo+4294967281>: callq 0x401106 <baz>
> 0x401116 <foo+4294967286>: nop
> 0x401117 <foo+4294967287>: pop %rbp
>
> This commit, in conjuction with an earlier patch from this series, causes
> cases like the above to be displayed like this (below) instead:
>
> (gdb) x/5i foo_cold
> 0x40110d <foo_cold>: push %rbp
> 0x40110e <foo-18>: mov %rsp,%rbp
> 0x401111 <foo-15>: callq 0x401106 <baz>
> 0x401116 <foo-10>: nop
> 0x401117 <foo-9>: pop %rbp
>
> Note that the address of foo_cold is now (due to another patch) being
> displayed as <foo_cold> instead of <foo+BigOffset>. The subsequent
> lines are shown as negative offsets from foo.
>
> Disassembly using the "disassemble" command is somewhat affected by
> these changes:
>
> Before:
>
> (gdb) disassemble foo_cold
> Dump of assembler code for function foo:
> Address range 0x401120 to 0x40113b:
> 0x0000000000401120 <+0>: push %rbp
> 0x0000000000401121 <+1>: mov %rsp,%rbp
> 0x0000000000401124 <+4>: callq 0x401119 <bar>
> 0x0000000000401129 <+9>: mov 0x2ef1(%rip),%eax # 0x404020 <e>
> 0x000000000040112f <+15>: test %eax,%eax
> 0x0000000000401131 <+17>: je 0x401138 <foo+24>
> 0x0000000000401133 <+19>: callq 0x40110d <foo+4294967277>
> 0x0000000000401138 <+24>: nop
> 0x0000000000401139 <+25>: pop %rbp
> 0x000000000040113a <+26>: retq
> Address range 0x40110d to 0x401119:
> 0x000000000040110d <+-19>: push %rbp
> 0x000000000040110e <+-18>: mov %rsp,%rbp
> 0x0000000000401111 <+-15>: callq 0x401106 <baz>
> 0x0000000000401116 <+-10>: nop
> 0x0000000000401117 <+-9>: pop %rbp
> 0x0000000000401118 <+-8>: retq
> End of assembler dump.
>
> After:
>
> (gdb) disassemble foo_cold
> Dump of assembler code for function foo:
> Address range 0x401120 to 0x40113b:
> 0x0000000000401120 <+0>: push %rbp
> 0x0000000000401121 <+1>: mov %rsp,%rbp
> 0x0000000000401124 <+4>: callq 0x401119 <bar>
> 0x0000000000401129 <+9>: mov 0x2ef1(%rip),%eax # 0x404020 <e>
> 0x000000000040112f <+15>: test %eax,%eax
> 0x0000000000401131 <+17>: je 0x401138 <foo+24>
> 0x0000000000401133 <+19>: callq 0x40110d <foo_cold>
> 0x0000000000401138 <+24>: nop
> 0x0000000000401139 <+25>: pop %rbp
> 0x000000000040113a <+26>: retq
> Address range 0x40110d to 0x401119:
> 0x000000000040110d <-19>: push %rbp
> 0x000000000040110e <-18>: mov %rsp,%rbp
> 0x0000000000401111 <-15>: callq 0x401106 <baz>
> 0x0000000000401116 <-10>: nop
> 0x0000000000401117 <-9>: pop %rbp
> 0x0000000000401118 <-8>: retq
> End of assembler dump.
>
> Note that negative offsets are now displayed without the leading "+".
> Also, the callq to foo_cold is now displayed as such instead of a callq
> to foo with a large positive offset.
>
> gdb/ChangeLog:
>
> * printcmd.c (print_address_symbolic): Print negative offsets.
> (build_address_symbolic): Force signed arithmetic when computing
> offset.
> ---
> gdb/printcmd.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/gdb/printcmd.c b/gdb/printcmd.c
> index 1109cb3046..dce6ab2db9 100644
> --- a/gdb/printcmd.c
> +++ b/gdb/printcmd.c
> @@ -539,7 +539,7 @@ print_address_symbolic (struct gdbarch *gdbarch, CORE_ADDR addr,
> fputs_filtered ("<", stream);
> fputs_styled (name.c_str (), function_name_style.style (), stream);
> if (offset != 0)
> - fprintf_filtered (stream, "+%u", (unsigned int) offset);
> + fprintf_filtered (stream, "%+d", offset);
>
> /* Append source filename and line number if desired. Give specific
> line # of this addr, if we have it; else line # of the nearest symbol. */
> @@ -679,7 +679,7 @@ build_address_symbolic (struct gdbarch *gdbarch,
> && name_location + max_symbolic_offset > name_location)
> return 1;
>
> - *offset = addr - name_location;
> + *offset = (LONGEST) addr - name_location;
>
> *name = name_temp;
>
> --
> 2.21.0
>
More information about the Gdb-patches
mailing list