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* [Bug record/31487] New: [RFE] reverse debugging should print the previous line
@ 2024-03-14 13:19 blarsen at redhat dot com
2024-03-14 15:30 ` [Bug record/31487] " ssbssa at sourceware dot org
0 siblings, 1 reply; 2+ messages in thread
From: blarsen at redhat dot com @ 2024-03-14 13:19 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31487
Bug ID: 31487
Summary: [RFE] reverse debugging should print the previous line
Product: gdb
Version: HEAD
Status: NEW
Severity: normal
Priority: P2
Component: record
Assignee: unassigned at sourceware dot org
Reporter: blarsen at redhat dot com
Target Milestone: ---
When GDB has the execution direction to reverse and attempts to print the
current line, it considers the current PC, sees that it is at the start of a
line and prints that line. This is a nuissance because using "next" or "step"
in this case will undo a different line than the one printed. For example, see
the following session:
Temporary breakpoint 2, main () at t.c:23
23 int p = 0;
(gdb) record
(gdb) next
24 setup (n);
(gdb) next
25 for(int i = 0; i<10; i++) proc[i] = -1;
(gdb) set exec-direction reverse
(gdb) next
24 setup (n);
(gdb) step
No more reverse-execution history.
main () at t.c:23
23 int p = 0;
(gdb)
As a user, seeing the "setup" line, I would expect the "step" command to enter
the 'setup' function, instead of undoing the previous line. My suggestion would
be for GDB to instead provide this session:
Temporary breakpoint 2, main () at t.c:23
23 int p = 0;
(gdb) record
(gdb) next
24 setup (n);
(gdb) next
25 for(int i = 0; i<10; i++) proc[i] = -1;
(gdb) set exec-direction reverse
24 setup (n);
(gdb) next
23 int p = 0;
(gdb) step
No more reverse-execution history.
main () at t.c:23
23 int p = 0;
(gdb)
To do this, a remote target would need to provide a "previous PC" style method,
so that we are able to identify the previous-executed line correctly. We should
also be able to handle when a reverse-executing target is not able to provide
it, since it isn't feasible with all recording methods. This may not be a
trivial issue to solve.
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* [Bug record/31487] [RFE] reverse debugging should print the previous line
2024-03-14 13:19 [Bug record/31487] New: [RFE] reverse debugging should print the previous line blarsen at redhat dot com
@ 2024-03-14 15:30 ` ssbssa at sourceware dot org
0 siblings, 0 replies; 2+ messages in thread
From: ssbssa at sourceware dot org @ 2024-03-14 15:30 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=31487
Hannes Domani <ssbssa at sourceware dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ssbssa at sourceware dot org
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2024-03-14 13:19 [Bug record/31487] New: [RFE] reverse debugging should print the previous line blarsen at redhat dot com
2024-03-14 15:30 ` [Bug record/31487] " ssbssa at sourceware dot org
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