[PATCH][gdb/breakpoint] Handle setting breakpoint on label without address

Tom de Vries
2020-08-27T11:52:20Z

Hi,

Consider test-case test.c:
...
$ cat test.c
int main (void) {
return 0;
L1:
(void)0;
}
...

Compiled with debug info:
...
$ gcc test.c -g
...

When attempting to set a breakpoint at L1, which is a label without address:
...
<1><f4>: Abbrev Number: 2 (DW_TAG_subprogram)
<f5> DW_AT_name : main
<2><115>: Abbrev Number: 3 (DW_TAG_label)
<116> DW_AT_name : L1
<119> DW_AT_decl_file : 1
<11a> DW_AT_decl_line : 5
<2><11b>: Abbrev Number: 0
...
we run into an internal-error:
...
$ gdb -batch a.out -ex "b main:L1"
linespec.c:3233: internal-error: void decode_line_full(const event_location*, int, program_space*, symtab*, int, linespec_result*, const char*, const char*): Assertion `result.size () == 1 || canonical->pre_expanded' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
...

Fix this by detecting the error condition in decode_line_full instead, and
throwing an error, such that we have instead:
...
(gdb) b main:L1
Location main:L1 not available
(gdb)
...

Unfortunately, to call event_location_to_string, which is used to get the
location name in the error message, we need to pass a non-const struct
event_location, because the call may cache the string in the struct (See
EL_STRING). So, we change the prototype of decode_line_full accordingly, and
everywhere this propages to.

Tested on x86_64-linux.

Any comments?

Thanks,
- Tom

[gdb/breakpoint] Handle setting breakpoint on label without address

gdb/ChangeLog:

2020-08-27 Tom de Vries <tdevries@suse.de>

PR breakpoint/26544
* breakpoint.c (parse_breakpoint_sals): Remove const from struct
event_location.
(create_breakpoint): Same.
(base_breakpoint_decode_location): Same.
(bkpt_create_sals_from_location): Same.
(bkpt_decode_location): Same.
(bkpt_probe_create_sals_from_location): Same.
(bkpt_probe_decode_location): Same.
(tracepoint_create_sals_from_location): Same.
(tracepoint_decode_location): Same.
(tracepoint_probe_decode_location): Same.
(strace_marker_create_sals_from_location): Same.
(strace_marker_decode_location): Same.
(create_sals_from_location_default): Same.
(decode_location_default): Same.
* breakpoint.h (struct breakpoint_ops): Same.
(create_breakpoint): Same.
* linespec.h (decode_line_full): Same.
* linespec.c (decode_line_full): Same. Throw error if
result.size () == 0.

gdb/testsuite/ChangeLog:

2020-08-27 Tom de Vries <tdevries@suse.de>

* gdb.base/label-without-address.c: New test.
* gdb.base/label-without-address.exp: New file.

---
gdb/breakpoint.c | 36 ++++++++++----------
gdb/breakpoint.h | 6 ++--
gdb/linespec.c | 6 +++-
gdb/linespec.h | 2 +-
gdb/testsuite/gdb.base/label-without-address.c | 24 ++++++++++++++
gdb/testsuite/gdb.base/label-without-address.exp | 42 ++++++++++++++++++++++++
6 files changed, 93 insertions(+), 23 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index ef8e54f634..879d61f4b9 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -89,7 +89,7 @@ static void map_breakpoint_numbers (const char *,
static void breakpoint_re_set_default (struct breakpoint *);

static void
- create_sals_from_location_default (const struct event_location *location,
+ create_sals_from_location_default (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted);

@@ -104,7 +104,7 @@ static void create_breakpoints_sal_default (struct gdbarch *,
int, int, int, unsigned);

static std::vector<symtab_and_line> decode_location_default
- (struct breakpoint *b, const struct event_location *location,
+ (struct breakpoint *b, struct event_location *location,
struct program_space *search_pspace);

static int can_use_hardware_watchpoint
@@ -8948,7 +8948,7 @@ create_breakpoints_sal (struct gdbarch *gdbarch,
the caller's responsibility to free them. */

static void
-parse_breakpoint_sals (const struct event_location *location,
+parse_breakpoint_sals (struct event_location *location,
struct linespec_result *canonical)
{
struct symtab_and_line cursal;
@@ -9213,7 +9213,7 @@ breakpoint_ops_for_event_location (const struct event_location *location,

int
create_breakpoint (struct gdbarch *gdbarch,
- const struct event_location *location,
+ struct event_location *location,
const char *cond_string,
int thread, const char *extra_string,
int parse_extra,
@@ -12271,7 +12271,7 @@ base_breakpoint_print_recreate (struct breakpoint *b, struct ui_file *fp)

static void
base_breakpoint_create_sals_from_location
- (const struct event_location *location,
+ (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted)
{
@@ -12296,7 +12296,7 @@ base_breakpoint_create_breakpoints_sal (struct gdbarch *gdbarch,

static std::vector<symtab_and_line>
base_breakpoint_decode_location (struct breakpoint *b,
- const struct event_location *location,
+ struct event_location *location,
struct program_space *search_pspace)
{
internal_error_pure_virtual_called ();
@@ -12519,7 +12519,7 @@ bkpt_print_recreate (struct breakpoint *tp, struct ui_file *fp)
}

static void
-bkpt_create_sals_from_location (const struct event_location *location,
+bkpt_create_sals_from_location (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted)
{
@@ -12550,7 +12550,7 @@ bkpt_create_breakpoints_sal (struct gdbarch *gdbarch,

static std::vector<symtab_and_line>
bkpt_decode_location (struct breakpoint *b,
- const struct event_location *location,
+ struct event_location *location,
struct program_space *search_pspace)
{
return decode_location_default (b, location, search_pspace);
@@ -12723,7 +12723,7 @@ bkpt_probe_remove_location (struct bp_location *bl,
}

static void
-bkpt_probe_create_sals_from_location (const struct event_location *location,
+bkpt_probe_create_sals_from_location (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted)
{
@@ -12737,7 +12737,7 @@ bkpt_probe_create_sals_from_location (const struct event_location *location,

static std::vector<symtab_and_line>
bkpt_probe_decode_location (struct breakpoint *b,
- const struct event_location *location,
+ struct event_location *location,
struct program_space *search_pspace)
{
std::vector<symtab_and_line> sals = parse_probes (location, search_pspace, NULL);
@@ -12831,7 +12831,7 @@ tracepoint_print_recreate (struct breakpoint *self, struct ui_file *fp)
}

static void
-tracepoint_create_sals_from_location (const struct event_location *location,
+tracepoint_create_sals_from_location (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted)
{
@@ -12862,7 +12862,7 @@ tracepoint_create_breakpoints_sal (struct gdbarch *gdbarch,

static std::vector<symtab_and_line>
tracepoint_decode_location (struct breakpoint *b,
- const struct event_location *location,
+ struct event_location *location,
struct program_space *search_pspace)
{
return decode_location_default (b, location, search_pspace);
@@ -12874,7 +12874,7 @@ struct breakpoint_ops tracepoint_breakpoint_ops;

static void
tracepoint_probe_create_sals_from_location
- (const struct event_location *location,
+ (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted)
{
@@ -12884,7 +12884,7 @@ tracepoint_probe_create_sals_from_location

static std::vector<symtab_and_line>
tracepoint_probe_decode_location (struct breakpoint *b,
- const struct event_location *location,
+ struct event_location *location,
struct program_space *search_pspace)
{
/* We use the same method for breakpoint on probes. */
@@ -12965,7 +12965,7 @@ dprintf_after_condition_true (struct bpstats *bs)
markers (`-m'). */

static void
-strace_marker_create_sals_from_location (const struct event_location *location,
+strace_marker_create_sals_from_location (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted)
{
@@ -13035,7 +13035,7 @@ strace_marker_create_breakpoints_sal (struct gdbarch *gdbarch,

static std::vector<symtab_and_line>
strace_marker_decode_location (struct breakpoint *b,
- const struct event_location *location,
+ struct event_location *location,
struct program_space *search_pspace)
{
struct tracepoint *tp = (struct tracepoint *) b;
@@ -13718,7 +13718,7 @@ breakpoint_re_set_default (struct breakpoint *b)
calls parse_breakpoint_sals. Return 1 for success, zero for failure. */

static void
-create_sals_from_location_default (const struct event_location *location,
+create_sals_from_location_default (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted)
{
@@ -13755,7 +13755,7 @@ create_breakpoints_sal_default (struct gdbarch *gdbarch,

static std::vector<symtab_and_line>
decode_location_default (struct breakpoint *b,
- const struct event_location *location,
+ struct event_location *location,
struct program_space *search_pspace)
{
struct linespec_result canonical;
diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index 347aeb75f3..a5fead9149 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -609,7 +609,7 @@ struct breakpoint_ops
`create_sals_from_location_default'.

This function is called inside `create_breakpoint'. */
- void (*create_sals_from_location) (const struct event_location *location,
+ void (*create_sals_from_location) (struct event_location *location,
struct linespec_result *canonical,
enum bptype type_wanted);

@@ -636,7 +636,7 @@ struct breakpoint_ops
This function is called inside `location_to_sals'. */
std::vector<symtab_and_line> (*decode_location)
(struct breakpoint *b,
- const struct event_location *location,
+ struct event_location *location,
struct program_space *search_pspace);

/* Return true if this breakpoint explains a signal. See
@@ -1386,7 +1386,7 @@ enum breakpoint_create_flags
Returns true if any breakpoint was created; false otherwise. */

extern int create_breakpoint (struct gdbarch *gdbarch,
- const struct event_location *location,
+ struct event_location *location,
const char *cond_string, int thread,
const char *extra_string,
int parse_extra,
diff --git a/gdb/linespec.c b/gdb/linespec.c
index 4a634e3aff..e8f3d594c3 100644
--- a/gdb/linespec.c
+++ b/gdb/linespec.c
@@ -3201,7 +3201,7 @@ event_location_to_sals (linespec_parser *parser,
/* See linespec.h. */

void
-decode_line_full (const struct event_location *location, int flags,
+decode_line_full (struct event_location *location, int flags,
struct program_space *search_pspace,
struct symtab *default_symtab,
int default_line, struct linespec_result *canonical,
@@ -3230,6 +3230,10 @@ decode_line_full (const struct event_location *location, int flags,
location);
state = PARSER_STATE (&parser);

+ if (result.size () == 0)
+ throw_error (NOT_SUPPORTED_ERROR, _("Location %s not available"),
+ event_location_to_string (location));
+
gdb_assert (result.size () == 1 || canonical->pre_expanded);
canonical->pre_expanded = 1;

diff --git a/gdb/linespec.h b/gdb/linespec.h
index 2a34f60f05..9c2c8988fb 100644
--- a/gdb/linespec.h
+++ b/gdb/linespec.h
@@ -124,7 +124,7 @@ extern std::vector<symtab_and_line>
strcmp sense) to FILTER will be returned; all others will be
filtered out. */

-extern void decode_line_full (const struct event_location *location, int flags,
+extern void decode_line_full (struct event_location *location, int flags,
struct program_space *search_pspace,
struct symtab *default_symtab, int default_line,
struct linespec_result *canonical,
diff --git a/gdb/testsuite/gdb.base/label-without-address.c b/gdb/testsuite/gdb.base/label-without-address.c
new file mode 100644
index 0000000000..f0d4a42268
--- /dev/null
+++ b/gdb/testsuite/gdb.base/label-without-address.c
@@ -0,0 +1,24 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2020 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+int
+main (void)
+{
+ return 0;
+ L1:
+ (void)0;
+}
diff --git a/gdb/testsuite/gdb.base/label-without-address.exp b/gdb/testsuite/gdb.base/label-without-address.exp
new file mode 100644
index 0000000000..eda68a4b0a
--- /dev/null
+++ b/gdb/testsuite/gdb.base/label-without-address.exp
@@ -0,0 +1,42 @@
+# Copyright 2020 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
+ return -1
+}
+
+if ![runto_main] then {
+ fail "can't run to main"
+ return 0
+}
+
+set supported 0
+gdb_test_multiple "l main:L1" "" {
+ -wrap -re "No label \"L1\" defined in function \"main\"\." {
+ unsupported $gdb_test_name
+ }
+ -wrap -re "L1:\r\n.*" {
+ pass $gdb_test_name
+ set supported 1
+ }
+}
+
+if { ! $supported } {
+ return -1
+}
+
+gdb_test "break L1" "Location L1 not available"