[PATCH 1/2] Used chunk needs to be removed from free_list

["Torbjörn SVENSSON" <torbjorn.svensson@foss.st.com>]

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