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Allow display of negative offsets in print_address_symbolic()

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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.
This commit is contained in:
Kevin Buettner 2019-06-02 18:12:28 -07:00
parent 2906593ffe
commit a1530dc731
2 changed files with 8 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
gdb/ChangeLog
View File

@ -1,3 +1,9 @@
2019-07-30 Kevin Buettner <kevinb@redhat.com>
* printcmd.c (print_address_symbolic): Print negative offsets.
(build_address_symbolic): Force signed arithmetic when computing
offset.
2019-07-30 Christian Biesinger <cbiesinger@google.com>
PR/24474: Add a function to lookup static variables.
@ -84,10 +90,6 @@
* dwarf2-frame.c (dwarf2_frame_cache): Don't decode FDE instructions
for entry pc when entry pc is out of range for that FDE.
* printcmd.c (print_address_symbolic): Print negative offsets.
(build_address_symbolic): Force signed arithmetic when computing
offset.
2019-07-26 Brian Callahan <bcallah@openbsd.org>
PR gdb/24839:

4
gdb/printcmd.c
View File

@ -540,7 +540,7 @@ 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. */
@ -680,7 +680,7 @@ 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;