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gdb: Handle requests to print source lines backward

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...by which I mean from high line number to low, not, actually
backward character by character!

Commit:

  commit 62f29fda90
  Date:   Tue Oct 9 22:21:05 2018 -0600

      Highlight source code using GNU Source Highlight

introduced a regression in the test gdb.linespec/explicit.exp, in
which a request is made to GDB to print a reverse sequence of lines,
from +10 to -10 from the current line number.  The expected behaviour
is that GDB prints nothing.  The above commit changed this so that GDB
now prints:

  Line number 32 out of range; /path/to/gdb/testsuite/gdb.linespec/explicit.c has 71 lines.

which is a little confusing.

This commit fixes the regression, and restores the behaviour that GDB
prints nothing.

While I was passing I noticed a call to `back` on a std::string that I
was concerned could be empty if the request for source lines returns
an empty string.  I don't know if it would be possible for a request
for lines to return an empty string, I guess it should be impossible,
in which case, maybe this should be an assertion, but adding a `empty`
check, seems like an easy and cheap safety net.

gdb/ChangeLog:

	* source.c (print_source_lines_base): Handle requests to print
	reverse line number sequences, and guard against empty lines
	string.
This commit is contained in:
Andrew Burgess 2019-01-06 23:53:22 +00:00
parent 62ea19c100
commit ec98a4ad5b
2 changed files with 17 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

6
gdb/ChangeLog
View file

@ -1,3 +1,9 @@
2019-01-08 Andrew Burgess <andrew.burgess@embecosm.com>
* source.c (print_source_lines_base): Handle requests to print
reverse line number sequences, and guard against empty lines
string.
2019-01-08 Andrew Burgess <andrew.burgess@embecosm.com> 2019-01-08 Andrew Burgess <andrew.burgess@embecosm.com>
* source.c (print_source_lines_base): Fix skip of '\r' if next * source.c (print_source_lines_base): Fix skip of '\r' if next

12
gdb/source.c
View file

@ -1346,6 +1346,16 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
last_source_error = 0; last_source_error = 0;
/* If the user requested a sequence of lines that seems to go backward
(from high to low line numbers) then we don't print anything.
The use of '- 1' here instead of '<=' is currently critical, we rely
on the undefined wrap around behaviour of 'int' for stopline. When
the use has done: 'set listsize unlimited' then stopline can overflow
and appear as MIN_INT. This is a long-standing bug that needs
fixing. */
if (stopline - 1 < line)
return;
std::string lines; std::string lines;
if (!g_source_cache.get_source_lines (s, line, stopline - 1, &lines)) if (!g_source_cache.get_source_lines (s, line, stopline - 1, &lines))
error (_("Line number %d out of range; %s has %d lines."), error (_("Line number %d out of range; %s has %d lines."),
@ -1392,7 +1402,7 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
if (c == '\0') if (c == '\0')
break; break;
} }
if (lines.back () != '\n') if (!lines.empty() && lines.back () != '\n')
uiout->text ("\n"); uiout->text ("\n");
} }