[PATCHv2 2/9] gdb: create_breakpoint: asserts relating to extra_string/parse_extra

Andrew Burgess via Gdb-patches
2023-05-15T19:28:53Z

The goal of this commit is to better define the API for
create_breakpoint especially around the use of extra_string and
parse_extra. This will be useful in the next commit when I plan to
make some changes to create_breakpoint.

This commit makes one possibly breaking change: until this commit it
was possible to create thread-specific dprintf breakpoint like this:

(gdb) dprintf call_me, thread 1 "%s", "hello"
Dprintf 2 at 0x401152: file /tmp/hello.c, line 8.
(gdb) info breakpoints
Num Type Disp Enb Address What
2 dprintf keep y 0x0000000000401152 in call_me at /tmp/hello.c:8 thread 1
stop only in thread 1
printf "%s", "hello"
(gdb)

this feature of dprintf was not documented, was not tested, and is
slightly different in syntax to how we create thread specific
breakpoints and/or watchpoints -- the thread condition appears after
the first ','.

I believe that this worked at all was simply by luck. We happen to
pass the parse_extra flag as true from dprintf_command to
create_breakpoint.

So in this commit I made the choice change this. We now pass
parse_extra as false from dprintf_command to create_breakpoint. With
this done it is assumed that the only thing in the extra_string is the
dprintf format and arguments.

Beyond this change I've updated the comment on create_breakpoint in
breakpoint.h, and I've then added some asserts into
create_breakpoint as well as moving around some of the error
handling.

- We now assert on the incoming argument values,

- I've moved an error check to sit after the call to
find_condition_and_thread_for_sals, this ensures the extra_string
was parsed correctly,

In dprintf_command:

- We now throw an error if there is no format string after the
dprintf location. This error was already being thrown, but was
being caught later in the process. With this change we catch the
missing string earlier,

- And, as mentioned earlier, we pass parse_extra as false when
calling create_breakpoint,

In create_tracepoint_from_upload:

- We now throw an error if the parsed location doesn't completely
consume the addr_str variable. This error has now effectively
moved out of create_breakpoint.
---
gdb/breakpoint.c | 42 +++++++++++++++++++++++++++++-------------
gdb/breakpoint.h | 38 ++++++++++++++++++++++++--------------
2 files changed, 53 insertions(+), 27 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 31448e0a895..4d182ac0143 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -9035,6 +9035,17 @@ create_breakpoint (struct gdbarch *gdbarch,
if (extra_string != NULL && *extra_string == '\0')
extra_string = NULL;

+ /* A bp_dprintf must always have an accompanying EXTRA_STRING containing
+ the dprintf format and arguments -- PARSE_EXTRA should always be false
+ in this case.
+
+ For all other breakpoint types, EXTRA_STRING should be nullptr unless
+ PARSE_EXTRA is true. */
+ gdb_assert ((type_wanted == bp_dprintf
+ && extra_string != nullptr && !parse_extra)
+ || (type_wanted != bp_dprintf
+ && (extra_string == nullptr || parse_extra)));
+
try
{
ops->create_sals_from_location_spec (locspec, &canonical);
@@ -9098,6 +9109,8 @@ create_breakpoint (struct gdbarch *gdbarch,

if (parse_extra)
{
+ gdb_assert (type_wanted != bp_dprintf);
+
gdb::unique_xmalloc_ptr<char> rest;
gdb::unique_xmalloc_ptr<char> cond;

@@ -9105,15 +9118,15 @@ create_breakpoint (struct gdbarch *gdbarch,

find_condition_and_thread_for_sals (lsal.sals, extra_string,
&cond, &thread, &task, &rest);
+
+ if (rest.get () != nullptr && *(rest.get ()) != '\0')
+ error (_("Garbage '%s' at end of command"), rest.get ());
+
cond_string_copy = std::move (cond);
extra_string_copy = std::move (rest);
}
else
{
- if (type_wanted != bp_dprintf
- && extra_string != NULL && *extra_string != '\0')
- error (_("Garbage '%s' at end of location"), extra_string);
-
/* Check the validity of the condition. We should error out
if the condition is invalid at all of the locations and
if it is not forced. In the PARSE_EXTRA case above, this
@@ -9322,20 +9335,17 @@ dprintf_command (const char *arg, int from_tty)

/* If non-NULL, ARG should have been advanced past the location;
the next character must be ','. */
- if (arg != NULL)
+ if (arg == nullptr || arg[0] != ',' || arg[1] == '\0')
+ error (_("Format string required"));
+ else
{
- if (arg[0] != ',' || arg[1] == '\0')
- error (_("Format string required"));
- else
- {
- /* Skip the comma. */
- ++arg;
- }
+ /* Skip the comma. */
+ ++arg;
}

create_breakpoint (get_current_arch (),
locspec.get (),
- NULL, 0, arg, false, 1 /* parse arg */,
+ NULL, -1, arg, false, 0 /* parse arg */,
0, bp_dprintf,
0 /* Ignore count */,
pending_break_support,
@@ -13910,6 +13920,12 @@ create_tracepoint_from_upload (struct uploaded_tp *utp)

location_spec_up locspec = string_to_location_spec (&addr_str,
current_language);
+
+
+ gdb_assert (addr_str != nullptr);
+ if (*addr_str != '\0')
+ error (_("Garbage '%s' at end of location"), addr_str);
+
if (!create_breakpoint (get_current_arch (),
locspec.get (),
utp->cond_string.get (), -1, addr_str,
diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index e57dc2523fb..2adcc9fa338 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -1515,26 +1515,36 @@ enum breakpoint_create_flags
functions for setting a breakpoint at LOCSPEC.

This function has two major modes of operations, selected by the
- PARSE_EXTRA parameter.
+ PARSE_EXTRA and WANTED_TYPE parameters.

- If PARSE_EXTRA is zero, LOCSPEC is just the breakpoint's location
- spec, with condition, thread, and extra string specified by the
- COND_STRING, THREAD, and EXTRA_STRING parameters.
+ When WANTED_TYPE is not bp_dprintf the following rules apply:

- If PARSE_EXTRA is non-zero, this function will attempt to extract
- the condition, thread, and extra string from EXTRA_STRING, ignoring
- the similarly named parameters.
+ If PARSE_EXTRA is zero, LOCSPEC is just the breakpoint's location
+ spec, with condition, thread, and extra string specified by the
+ COND_STRING, THREAD, and EXTRA_STRING parameters.

- If FORCE_CONDITION is true, the condition is accepted even when it is
- invalid at all of the locations. However, if PARSE_EXTRA is non-zero,
- the FORCE_CONDITION parameter is ignored and the corresponding argument
- is parsed from EXTRA_STRING.
+ If PARSE_EXTRA is non-zero, this function will attempt to extract the
+ condition, thread, and extra string from EXTRA_STRING, ignoring the
+ similarly named parameters.
+
+ When WANTED_TYPE is bp_dprintf the following rules apply:
+
+ PARSE_EXTRA must always be zero, LOCSPEC is just the breakpoint's
+ location spec, with condition, thread, and extra string (which
+ contains the dprintf format and arguments) specified by the
+ COND_STRING, THREAD, and EXTRA_STRING parameters.
+
+ If FORCE_CONDITION is true, the condition (in COND_STRING) is accepted
+ even when it is invalid at all of the locations. However, if
+ PARSE_EXTRA is non-zero and WANTED_TYPE is not bp_dprintf, the
+ FORCE_CONDITION parameter is ignored and the corresponding argument is
+ parsed from EXTRA_STRING.

The THREAD should be a global thread number, the created breakpoint will
only apply for that thread. If the breakpoint should apply for all
- threads then pass -1. However, if PARSE_EXTRA is non-zero then the
- THREAD parameter is ignored and an optional thread number will be parsed
- from EXTRA_STRING.
+ threads then pass -1. However, if PARSE_EXTRA is non-zero and
+ WANTED_TYPE is not bp_dprintf, then the THREAD parameter is ignored and
+ an optional thread number will be parsed from EXTRA_STRING.

If INTERNAL is non-zero, the breakpoint number will be allocated
from the internal breakpoint count.
--
2.25.4