[PATCH v2 4/5] Allow display of negative offsets in print_address_symbolic()
Kevin Buettner
kevinb@redhat.com
Thu Jul 4 05:05:00 GMT 2019
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
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