Similar to COPY_ARRAY (introduced in 60566cbb58), add a safe and
convenient helper for moving potentially overlapping ranges of array
entries. It infers the element size, multiplies automatically and
safely to get the size in bytes, does a basic type safety check by
comparing element sizes and unlike memmove(3) it supports NULL
pointers iff 0 elements are to be moved.
Also add a semantic patch to demonstrate the helper's intended usage.
Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
---
contrib/coccinelle/array.cocci | 17 +++++++++++++++++
git-compat-util.h | 8 ++++++++
2 files changed, 25 insertions(+)
diff --git a/contrib/coccinelle/array.cocci b/contrib/coccinelle/array.cocci
index 4ba98b7eaf..c61d1ca8dc 100644
--- a/contrib/coccinelle/array.cocci
+++ b/contrib/coccinelle/array.cocci
@@ -27,6 +27,23 @@ expression n;
@@
type T;
+T *dst;
+T *src;
+expression n;
+@@
+(
+- memmove(dst, src, (n) * sizeof(*dst));
++ MOVE_ARRAY(dst, src, n);
+|
+- memmove(dst, src, (n) * sizeof(*src));
++ MOVE_ARRAY(dst, src, n);
+|
+- memmove(dst, src, (n) * sizeof(T));
++ MOVE_ARRAY(dst, src, n);
+)
+
+@@
+type T;
T *ptr;
expression n;
@@
diff --git a/git-compat-util.h b/git-compat-util.h
index 047172d173..159f82154a 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -825,6 +825,14 @@ static inline void copy_array(void *dst, const void *src, size_t n, size_t size)
memcpy(dst, src, st_mult(size, n));
}
+#define MOVE_ARRAY(dst, src, n) move_array((dst), (src), (n), sizeof(*(dst)) + \
+ BUILD_ASSERT_OR_ZERO(sizeof(*(dst)) == sizeof(*(src))))
+static inline void move_array(void *dst, const void *src, size_t n, size_t size)
+{
+ if (n)
+ memmove(dst, src, st_mult(size, n));
+}
+
/*
* These functions help you allocate structs with flex arrays, and copy
* the data directly into the array. For example, if you had:
--
2.13.3
