[PATCH 08/20] libdtrace: grow module address ranges geometrically

[PATCH 08/20] libdtrace: grow module address ranges geometrically

[Kris Van Hees]

---
 libdtrace/dt_impl.h   |  2 ++
 libdtrace/dt_module.c | 21 +++++++++++++++------
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/libdtrace/dt_impl.h b/libdtrace/dt_impl.h
index fcdac855..f89ce2bc 100644
--- a/libdtrace/dt_impl.h
+++ b/libdtrace/dt_impl.h
@@ -149,8 +149,10 @@ typedef struct dt_module {
 
 	dtrace_addr_range_t *dm_text_addrs; /* text addresses, sorted */
 	size_t dm_text_addrs_size;	 /* number of entries */
+	size_t dm_text_addrs_cap;	 /* allocated entries */
 	dtrace_addr_range_t *dm_data_addrs; /* data/BSS addresses, sorted */
 	size_t dm_data_addrs_size;	 /* number of entries */
+	size_t dm_data_addrs_cap;	 /* allocated entries */
 
 	dt_idhash_t *dm_extern;	/* external symbol definitions */
 
diff --git a/libdtrace/dt_module.c b/libdtrace/dt_module.c
index 6868268e..7cc68968 100644
--- a/libdtrace/dt_module.c
+++ b/libdtrace/dt_module.c
@@ -1141,22 +1141,31 @@ dtrace_addr_range_grow(dt_module_t *dmp, int is_text)
 	dtrace_addr_range_t **range;
 	dtrace_addr_range_t *new_range;
 	dtrace_addr_range_t *final_range;
-	size_t *size;
+	size_t *size, *capacity;
 
 	if (is_text) {
 		range = &dmp->dm_text_addrs;
 		size = &dmp->dm_text_addrs_size;
+		capacity = &dmp->dm_text_addrs_cap;
 	} else {
 		range = &dmp->dm_data_addrs;
 		size = &dmp->dm_data_addrs_size;
+		capacity = &dmp->dm_data_addrs_cap;
 	}
 
-	new_range = realloc(*range, sizeof(struct dtrace_addr_range) *
-	    (*size+1));
-	if (new_range == NULL)
-		return NULL;
+	if (*size == *capacity) {
+		size_t cap = *capacity == 0 ? 4 : *capacity * 2;
 
-	*range = new_range;
+		if (cap < *capacity || cap > SIZE_MAX / sizeof(**range))
+			return NULL;
+		new_range = realloc(*range, sizeof(**range) * cap);
+		if (new_range == NULL)
+			return NULL;
+
+		*range = new_range;
+		*capacity = cap;
+	}
+	new_range = *range;
 	final_range = new_range + (*size);
 	final_range->dar_va = 0;
 	final_range->dar_size = 0;
-- 
2.52.0

Re: [PATCH 08/20] libdtrace: grow module address ranges geometrically

[Nick Alcock]

On 30 Oct 2026, Kris Van Hees verbalised:

> ---
>  libdtrace/dt_impl.h   |  2 ++
>  libdtrace/dt_module.c | 21 +++++++++++++++------
>  2 files changed, 17 insertions(+), 6 deletions(-)

I honestly thought we were already doing this.

Reviewed-by: Nick Alcock <nix@esperi.org.uk>

> -	new_range = realloc(*range, sizeof(struct dtrace_addr_range) *
> -	    (*size+1));

Ew. I am ashamed (though addr ranges are rare enough that it's probably
not *disastrous*, it's not good).

-- 
NULL && (void)