[newlib-cygwin] libm/stdlib: Realloc when shrinking by 2* or more

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=8a7ec55c535cddd74d45a2f6fb644ecded114de8

commit 8a7ec55c535cddd74d45a2f6fb644ecded114de8
Author: Keith Packard via Newlib <newlib@sourceware.org>
Date:   Thu Aug 13 17:19:02 2020 -0700

    libm/stdlib: Realloc when shrinking by 2* or more
    
    This reduces memory usage when reallocating objects much smaller.
    
    Signed-off-by: Keith Packard <keithp@keithp.com>

Diff:
---
 newlib/libc/stdlib/nano-mallocr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/newlib/libc/stdlib/nano-mallocr.c b/newlib/libc/stdlib/nano-mallocr.c
index 3970753a9..6ba0eb74b 100644
--- a/newlib/libc/stdlib/nano-mallocr.c
+++ b/newlib/libc/stdlib/nano-mallocr.c
@@ -476,15 +476,15 @@ void * nano_realloc(RARG void * ptr, malloc_size_t size)
         return NULL;
     }
 
-    /* TODO: There is chance to shrink the chunk if newly requested
-     * size is much small */
     old_size = nano_malloc_usable_size(RCALL ptr);
-    if (old_size >= size)
+    if (size <= old_size && (old_size >> 1) < size)
       return ptr;
 
     mem = nano_malloc(RCALL size);
     if (mem != NULL)
     {
+	if (old_size > size)
+	    old_size = size;
         memcpy(mem, ptr, old_size);
         nano_free(RCALL ptr);
     }