The macro ALLOC_GROW manages several aspects of dynamic memory
allocations for arrays: It performs overprovisioning in order to avoid
reallocations in future calls, updates the allocation size variable,
multiplies the item size and thus allows users to simply specify the
item count, performs the reallocation and updates the array pointer.
Sometimes this is too much. Add the macro REALLOCARRAY, which only
takes care of the latter three points and allows users to specify the
number of items an array can store directly. It can increase and
also decrease its size. Using this macro avoids duplicating the
array pointer name and takes care of item sizes automatically.
Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
---
Documentation/technical/api-allocation-growing.txt | 3 +++
git-compat-util.h | 2 ++
2 files changed, 5 insertions(+)
diff --git a/Documentation/technical/api-allocation-growing.txt b/Documentation/technical/api-allocation-growing.txt
index 542946b..4b5f049 100644
--- a/Documentation/technical/api-allocation-growing.txt
+++ b/Documentation/technical/api-allocation-growing.txt
@@ -34,3 +34,6 @@ item[nr++] = value you like;
------------
You are responsible for updating the `nr` variable.
+
+If you need to specify the number of elements to allocate explicitly
+then use the macro `REALLOCARRAY(item, alloc)` instead of `ALLOC_GROW`.
diff --git a/git-compat-util.h b/git-compat-util.h
index 4e7e3f8..d926e4c 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -626,6 +626,8 @@ extern int odb_mkstemp(char *template, size_t limit, const char *pattern);
extern int odb_pack_keep(char *name, size_t namesz, const unsigned char *sha1);
extern char *xgetcwd(void);
+#define REALLOCARRAY(x, alloc) x = xrealloc((x), (alloc) * sizeof(*(x)))
+
static inline size_t xsize_t(off_t len)
{
if (len > (size_t) len)
--
2.1.0
--
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