[PATCH 7/9] gdb: add all_bp_locations_at_addr function

Simon Marchi via Gdb-patches
2021-05-27T15:36:20Z

Add the all_bp_locations_at_addr function, which returns a range of all
breakpoint locations at exactly the given address. This lets us
replace:

bp_location *loc, **loc2p, *locp;
ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, address)
{
loc = *loc2p;

// use loc
}

with

for (bp_location *loc : all_bp_locations_at_addr (address))
{
// use loc
}

The all_bp_locations_at_addr returns a bp_locations_at_addr_range
object, which is really just a wrapper around two std::vector iterators
representing the beginning and end of the interesting range. These
iterators are found when constructing the bp_locations_at_addr_range
object using std::equal_range, which seems a perfect fit for this use
case.

One thing I noticed about the current ALL_BP_LOCATIONS_AT_ADDR is that
if you call it with a NULL start variable, that variable gets filled in
and can be re-used for subsequent iterations. This avoids the cost of
finding the start of the interesting range again for the subsequent
iterations. This happens in build_target_command_list, for example.
The same effect can be achieved by storing the range in a local
variable, it can be iterated on multiple times.

Note that the original comment over ALL_BP_LOCATIONS_AT_ADDR says:

Iterates through locations with address ADDRESS for the currently
selected program space.

I don't see anything restricting the iteration to a given program space,
as we iterate over all bp_locations, which as far as I know contains all
breakpoint locations, regardless of the program space. So I just
dropped that part of the comment.

gdb/ChangeLog:

* breakpoint.c (get_first_locp_gte_addr): Remove.
(ALL_BP_LOCATIONS_AT_ADDR): Remove. Replace all uses with
all_bp_locations_at_addr.
(struct bp_locations_at_addr_range): New.
(all_bp_locations_at_addr): New.
(bp_locations_compare_addrs): New.

Change-Id: Icc8c92302045c47a48f507b7f1872bdd31d4ba59
---
gdb/breakpoint.c | 258 ++++++++++++++++++++---------------------------
1 file changed, 110 insertions(+), 148 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 18cabee39846..79f82f29dff3 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -223,8 +223,6 @@ static void set_tracepoint_count (int num);

static bool is_masked_watchpoint (const struct breakpoint *b);

-static struct bp_location **get_first_locp_gte_addr (CORE_ADDR address);
-
/* Return 1 if B refers to a static tracepoint set by marker ("-m"), zero
otherwise. */

@@ -491,20 +489,6 @@ bool target_exact_watchpoints = false;
B ? (TMP=B->next, 1): 0; \
B = TMP)

-/* Iterates through locations with address ADDRESS for the currently selected
- program space. BP_LOCP_TMP points to each object. BP_LOCP_START points
- to where the loop should start from.
- If BP_LOCP_START is a NULL pointer, the macro automatically seeks the
- appropriate location to start with. */
-
-#define ALL_BP_LOCATIONS_AT_ADDR(BP_LOCP_TMP, BP_LOCP_START, ADDRESS) \
- for (BP_LOCP_START = BP_LOCP_START == NULL ? get_first_locp_gte_addr (ADDRESS) : BP_LOCP_START, \
- BP_LOCP_TMP = BP_LOCP_START; \
- BP_LOCP_START \
- && (BP_LOCP_TMP < bp_locations.data () + bp_locations.size () \
- && (*BP_LOCP_TMP)->address == ADDRESS); \
- BP_LOCP_TMP++)
-
/* Chains of all breakpoints defined. */

static struct breakpoint *breakpoint_chain;
@@ -553,6 +537,65 @@ all_bp_locations ()
return bp_locations;
}

+/* Range to iterate over breakpoint locations at a given address. */
+
+struct bp_locations_at_addr_range
+{
+ using iterator = std::vector<bp_location *>::iterator;
+
+ bp_locations_at_addr_range (CORE_ADDR addr)
+ {
+ struct compare
+ {
+ bool operator() (const bp_location *loc, CORE_ADDR addr_) const
+ { return loc->address < addr_; }
+
+ bool operator() (CORE_ADDR addr_, const bp_location *loc) const
+ { return addr_ < loc->address; }
+ };
+
+ auto it_pair = std::equal_range (bp_locations.begin (), bp_locations.end (),
+ addr, compare ());
+
+ m_begin = it_pair.first;
+ m_end = it_pair.second;
+ }
+
+ iterator begin () const
+ { return m_begin; }
+
+ iterator end () const
+ { return m_end; }
+
+private:
+ std::vector<bp_location *>::iterator m_begin;
+ std::vector<bp_location *>::iterator m_end;
+};
+
+/* Return a range to iterate over all breakpoint locations exactly at address
+ ADDR.
+
+ If it's needed to iterate multiple times on the same range, it's possible
+ to save the range in a local variable and use it multiple times:
+
+ auto range = all_bp_locations_at_addr (addr);
+
+ for (bp_location *loc : range)
+ // use loc
+
+ for (bp_location *loc : range)
+ // use loc
+
+ This saves a bit of time, as it avoids re-doing the binary searches to find
+ the range's boundaries. Just remember not to change the bp_locations vector
+ in the mean time, as it could make the range's iterators stale. */
+
+static bp_locations_at_addr_range
+all_bp_locations_at_addr (CORE_ADDR addr)
+{
+ return bp_locations_at_addr_range (addr);
+}
+
/* Maximum alignment offset between bp_target_info.PLACED_ADDRESS and
ADDRESS for the current elements of BP_LOCATIONS which get a valid
result from bp_location_has_shadow. You can use it for roughly
@@ -786,56 +829,6 @@ show_condition_evaluation_mode (struct ui_file *file, int from_tty,
value);
}

-/* A comparison function for bp_location AP and BP that is used by
- bsearch. This comparison function only cares about addresses, unlike
- the more general bp_location_is_less_than function. */
-
-static int
-bp_locations_compare_addrs (const void *ap, const void *bp)
-{
- const struct bp_location *a = *(const struct bp_location **) ap;
- const struct bp_location *b = *(const struct bp_location **) bp;
-
- if (a->address == b->address)
- return 0;
- else
- return ((a->address > b->address) - (a->address < b->address));
-}
-
-/* Helper function to skip all bp_locations with addresses
- less than ADDRESS. It returns the first bp_location that
- is greater than or equal to ADDRESS. If none is found, just
- return NULL. */
-
-static struct bp_location **
-get_first_locp_gte_addr (CORE_ADDR address)
-{
- struct bp_location dummy_loc;
- struct bp_location *dummy_locp = &dummy_loc;
- struct bp_location **locp_found = NULL;
-
- /* Initialize the dummy location's address field. */
- dummy_loc.address = address;
-
- /* Find a close match to the first location at ADDRESS. */
- locp_found = ((struct bp_location **)
- bsearch (&dummy_locp, bp_locations.data (), bp_locations.size (),
- sizeof (struct bp_location **),
- bp_locations_compare_addrs));
-
- /* Nothing was found, nothing left to do. */
- if (locp_found == NULL)
- return NULL;
-
- /* We may have found a location that is at ADDRESS but is not the first in the
- location's list. Go backwards (if possible) and locate the first one. */
- while ((locp_found - 1) >= bp_locations.data ()
- && (*(locp_found - 1))->address == address)
- locp_found--;
-
- return locp_found;
-}
-
/* Parse COND_STRING in the context of LOC and set as the condition
expression of LOC. BP_NUM is the number of LOC's owner, LOC_NUM is
the number of LOC within its owner. In case of parsing error, mark
@@ -2248,10 +2241,8 @@ parse_cond_to_aexpr (CORE_ADDR scope, struct expression *cond)
static void
build_target_condition_list (struct bp_location *bl)
{
- struct bp_location **locp = NULL, **loc2p;
int null_condition_or_parse_error = 0;
int modified = bl->needs_update;
- struct bp_location *loc;

/* Release conditions left over from a previous insert. */
bl->target_info.conditions.clear ();
@@ -2264,6 +2255,8 @@ build_target_condition_list (struct bp_location *bl)
|| !target_supports_evaluation_of_breakpoint_conditions ())
return;

+ auto loc_range = all_bp_locations_at_addr (bl->address);
+
/* Do a first pass to check for locations with no assigned
conditions or conditions that fail to parse to a valid agent
expression bytecode. If any of these happen, then it's no use to
@@ -2273,9 +2266,8 @@ build_target_condition_list (struct bp_location *bl)
even if the locations aren't considered duplicates (e.g.,
software breakpoint and hardware breakpoint at the same
address). */
- ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
+ for (bp_location *loc : loc_range)
{
- loc = (*loc2p);
if (is_breakpoint (loc->owner) && loc->pspace->num == bl->pspace->num)
{
if (modified)
@@ -2306,9 +2298,8 @@ build_target_condition_list (struct bp_location *bl)
being evaluated by GDB or the remote stub. */
if (null_condition_or_parse_error)
{
- ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
+ for (bp_location *loc : loc_range)
{
- loc = (*loc2p);
if (is_breakpoint (loc->owner) && loc->pspace->num == bl->pspace->num)
{
/* Only go as far as the first NULL bytecode is
@@ -2327,21 +2318,18 @@ build_target_condition_list (struct bp_location *bl)
considered duplicates, but we still marge all the conditions
anyway, as it's simpler, and doesn't really make a practical
difference. */
- ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
- {
- loc = (*loc2p);
- if (loc->cond
- && is_breakpoint (loc->owner)
- && loc->pspace->num == bl->pspace->num
- && loc->owner->enable_state == bp_enabled
- && loc->enabled
- && !loc->disabled_by_cond)
- {
- /* Add the condition to the vector. This will be used later
- to send the conditions to the target. */
- bl->target_info.conditions.push_back (loc->cond_bytecode.get ());
- }
- }
+ for (bp_location *loc : loc_range)
+ if (loc->cond
+ && is_breakpoint (loc->owner)
+ && loc->pspace->num == bl->pspace->num
+ && loc->owner->enable_state == bp_enabled
+ && loc->enabled
+ && !loc->disabled_by_cond)
+ {
+ /* Add the condition to the vector. This will be used later
+ to send the conditions to the target. */
+ bl->target_info.conditions.push_back (loc->cond_bytecode.get ());
+ }

return;
}
@@ -2430,10 +2418,8 @@ parse_cmd_to_aexpr (CORE_ADDR scope, char *cmd)
static void
build_target_command_list (struct bp_location *bl)
{
- struct bp_location **locp = NULL, **loc2p;
int null_command_or_parse_error = 0;
int modified = bl->needs_update;
- struct bp_location *loc;

/* Clear commands left over from a previous insert. */
bl->target_info.tcommands.clear ();
@@ -2445,27 +2431,25 @@ build_target_command_list (struct bp_location *bl)
if (dprintf_style != dprintf_style_agent)
return;

+ auto loc_range = all_bp_locations_at_addr (bl->address);
+
/* For now, if we have any location at the same address that isn't a
dprintf, don't install the target-side commands, as that would
make the breakpoint not be reported to the core, and we'd lose
control. */
- ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
- {
- loc = (*loc2p);
- if (is_breakpoint (loc->owner)
- && loc->pspace->num == bl->pspace->num
- && loc->owner->type != bp_dprintf)
- return;
- }
+ for (bp_location *loc : loc_range)
+ if (is_breakpoint (loc->owner)
+ && loc->pspace->num == bl->pspace->num
+ && loc->owner->type != bp_dprintf)
+ return;

/* Do a first pass to check for locations with no assigned
conditions or conditions that fail to parse to a valid agent expression
bytecode. If any of these happen, then it's no use to send conditions
to the target since this location will always trigger and generate a
response back to GDB. */
- ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
+ for (bp_location *loc : loc_range)
{
- loc = (*loc2p);
if (is_breakpoint (loc->owner) && loc->pspace->num == bl->pspace->num)
{
if (modified)
@@ -2493,20 +2477,17 @@ build_target_command_list (struct bp_location *bl)
and so clean up. */
if (null_command_or_parse_error)
{
- ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
- {
- loc = (*loc2p);
- if (is_breakpoint (loc->owner)
- && loc->pspace->num == bl->pspace->num)
- {
- /* Only go as far as the first NULL bytecode is
- located. */
- if (loc->cmd_bytecode == NULL)
- return;
+ for (bp_location *loc : loc_range)
+ if (is_breakpoint (loc->owner)
+ && loc->pspace->num == bl->pspace->num)
+ {
+ /* Only go as far as the first NULL bytecode is
+ located. */
+ if (loc->cmd_bytecode == NULL)
+ return;

- loc->cmd_bytecode.reset ();
- }
- }
+ loc->cmd_bytecode.reset ();
+ }
}

/* No NULL commands or failed bytecode generation. Build a command
@@ -2517,22 +2498,19 @@ build_target_command_list (struct bp_location *bl)
could end up running the commands twice. For the moment, we only
support targets-side commands with dprintf, but it doesn't hurt
to be pedantically correct in case that changes. */
- ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, bl->address)
- {
- loc = (*loc2p);
- if (breakpoint_locations_match (bl, loc)
- && loc->owner->extra_string
- && is_breakpoint (loc->owner)
- && loc->pspace->num == bl->pspace->num
- && loc->owner->enable_state == bp_enabled
- && loc->enabled
- && !loc->disabled_by_cond)
- {
- /* Add the command to the vector. This will be used later
- to send the commands to the target. */
- bl->target_info.tcommands.push_back (loc->cmd_bytecode.get ());
- }
- }
+ for (bp_location *loc : loc_range)
+ if (breakpoint_locations_match (bl, loc)
+ && loc->owner->extra_string
+ && is_breakpoint (loc->owner)
+ && loc->pspace->num == bl->pspace->num
+ && loc->owner->enable_state == bp_enabled
+ && loc->enabled
+ && !loc->disabled_by_cond)
+ {
+ /* Add the command to the vector. This will be used later
+ to send the commands to the target. */
+ bl->target_info.tcommands.push_back (loc->cmd_bytecode.get ());
+ }

bl->target_info.persist = 0;
/* Maybe flag this location as persistent. */
@@ -4190,12 +4168,8 @@ bp_location_inserted_here_p (struct bp_location *bl,
int
breakpoint_inserted_here_p (const address_space *aspace, CORE_ADDR pc)
{
- struct bp_location **blp, **blp_tmp = NULL;
-
- ALL_BP_LOCATIONS_AT_ADDR (blp, blp_tmp, pc)
+ for (bp_location *bl : all_bp_locations_at_addr (pc))
{
- struct bp_location *bl = *blp;
-
if (bl->loc_type != bp_loc_software_breakpoint
&& bl->loc_type != bp_loc_hardware_breakpoint)
continue;
@@ -4213,12 +4187,8 @@ int
software_breakpoint_inserted_here_p (const address_space *aspace,
CORE_ADDR pc)
{
- struct bp_location **blp, **blp_tmp = NULL;
-
- ALL_BP_LOCATIONS_AT_ADDR (blp, blp_tmp, pc)
+ for (bp_location *bl : all_bp_locations_at_addr (pc))
{
- struct bp_location *bl = *blp;
-
if (bl->loc_type != bp_loc_software_breakpoint)
continue;

@@ -4235,12 +4205,8 @@ int
hardware_breakpoint_inserted_here_p (const address_space *aspace,
CORE_ADDR pc)
{
- struct bp_location **blp, **blp_tmp = NULL;
-
- ALL_BP_LOCATIONS_AT_ADDR (blp, blp_tmp, pc)
+ for (bp_location *bl : all_bp_locations_at_addr (pc))
{
- struct bp_location *bl = *blp;
-
if (bl->loc_type != bp_loc_hardware_breakpoint)
continue;

@@ -11746,8 +11712,6 @@ swap_insertion (struct bp_location *left, struct bp_location *right)
static void
force_breakpoint_reinsertion (struct bp_location *bl)
{
- struct bp_location **locp = NULL, **loc2p;
- struct bp_location *loc;
CORE_ADDR address = 0;
int pspace_num;

@@ -11766,10 +11730,8 @@ force_breakpoint_reinsertion (struct bp_location *bl)
the same program space as the location
as "its condition has changed". We need to
update the conditions on the target's side. */
- ALL_BP_LOCATIONS_AT_ADDR (loc2p, locp, address)
+ for (bp_location *loc : all_bp_locations_at_addr (address))
{
- loc = *loc2p;
-
if (!is_breakpoint (loc->owner)
|| pspace_num != loc->pspace->num)
continue;
--
2.31.1