From: "Torbjörn SVENSSON" <torbjorn.svensson@foss.st.com>
To: <newlib@sourceware.org>
Subject: [PATCH 1/2] Used chunk needs to be removed from free_list
Date: Tue, 30 Aug 2022 15:56:25 +0200 [thread overview]
Message-ID: <20220830135625.2247198-1-torbjorn.svensson@foss.st.com> (raw)
Message-ID: <20220830135625.4kzESCVUBopSppIzQGGRdSumBGZ8pnNBaRB87yZtrwU@z> (raw)
When using nano malloc and the remaning heap space is not big enough to
fullfill the allocation, malloc will attempt to merge the last chunk in
the free list with a new allocation in order to create a bigger chunk.
This is successful, but the chunk still remains in the free_list, so
any later call to malloc can give out the same region without it first
being freed.
Possible sequence to verify:
void *p1 = malloc(3000);
void *p2 = malloc(4000);
void *p3 = malloc(5000);
void *p4 = malloc(6000);
void *p5 = malloc(7000);
free(p2);
free(p4);
void *p6 = malloc(35000);
free(p6);
void *p7 = malloc(42000);
void *p8 = malloc(32000);
Without the change, p7 and p8 points to the same address.
Requirement, after malloc(35000), there is less than 42000 bytes
available on the heap.
Contributed by STMicroelectronics
Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
---
newlib/libc/stdlib/nano-mallocr.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/newlib/libc/stdlib/nano-mallocr.c b/newlib/libc/stdlib/nano-mallocr.c
index 99ad60dd0..43eb20e07 100644
--- a/newlib/libc/stdlib/nano-mallocr.c
+++ b/newlib/libc/stdlib/nano-mallocr.c
@@ -336,6 +336,15 @@ void * nano_malloc(RARG malloc_size_t s)
if (sbrk_aligned(RCALL alloc_size) != (void *)-1)
{
p->size += alloc_size;
+
+ /* Remove chunk from free_list */
+ r = free_list;
+ while (r && p != r->next)
+ {
+ r = r->next;
+ }
+ r->next = NULL;
+
r = p;
}
else
--
2.25.1
next reply other threads:[~2022-08-30 13:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-30 13:56 Torbjörn SVENSSON [this message]
2022-08-30 13:56 ` Torbjörn SVENSSON
2022-08-30 13:56 ` [PATCH 2/2] Don't allocate another header when merging chunks Torbjörn SVENSSON
2022-08-30 13:56 ` Torbjörn SVENSSON
2022-09-01 18:44 ` Jeff Johnston
2022-09-01 19:04 ` Torbjorn SVENSSON
2022-09-01 19:36 ` Jeff Johnston
2022-09-01 19:39 ` Jeff Johnston
2022-09-01 18:41 ` [PATCH 1/2] Used chunk needs to be removed from free_list Jeff Johnston
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