[2/4] gdb: Handle requests to print source lines backward
Commit Message
...by which I mean from high line number to low, not, actually
backward character by character!
Commit:
commit 62f29fda90cf1d5a1899f57ef78452471c707fd6
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.
---
gdb/ChangeLog | 6 ++++++
gdb/source.c | 12 +++++++++++-
2 files changed, 17 insertions(+), 1 deletion(-)
Comments
>>>>> "Andrew" == Andrew Burgess <andrew.burgess@embecosm.com> writes:
Andrew> This commit fixes the regression, and restores the behaviour that GDB
Andrew> prints nothing.
Andrew> While I was passing I noticed a call to `back` on a std::string that I
Andrew> was concerned could be empty if the request for source lines returns
Andrew> an empty string. I don't know if it would be possible for a request
Andrew> for lines to return an empty string, I guess it should be impossible,
Andrew> in which case, maybe this should be an assertion, but adding a `empty`
Andrew> check, seems like an easy and cheap safety net.
Seems reasonable.
Andrew> * source.c (print_source_lines_base): Handle requests to print
Andrew> reverse line number sequences, and guard against empty lines
Andrew> string.
This is ok...
Andrew> + /* If the user requested a sequence of lines that seems to go backward
Andrew> + (from high to low line numbers) then we don't print anything.
Andrew> + The use of '- 1' here instead of '<=' is currently critical, we rely
Andrew> + on the undefined wrap around behaviour of 'int' for stopline. When
Andrew> + the use has done: 'set listsize unlimited' then stopline can overflow
Andrew> + and appear as MIN_INT. This is a long-standing bug that needs
Andrew> + fixing. */
... assuming this was the previous status quo.
Tom
@@ -1346,6 +1346,16 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
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;
if (!g_source_cache.get_source_lines (s, line, stopline - 1, &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')
break;
}
- if (lines.back () != '\n')
+ if (!lines.empty() && lines.back () != '\n')
uiout->text ("\n");
}