From: "René Scharfe" <l.s.r@web.de>
To: Git List <git@vger.kernel.org>
Cc: Junio C Hamano <gitster@pobox.com>, Jeff King <peff@peff.net>
Subject: [PATCH 1/2] add COPY_ARRAY
Date: Sun, 25 Sep 2016 09:15:42 +0200 [thread overview]
Message-ID: <6f402d35-b483-7552-2fb2-a5350112b8a6@web.de> (raw)
Add COPY_ARRAY, a safe and convenient helper for copying arrays,
complementing ALLOC_ARRAY and REALLOC_ARRAY. Users just specify source,
destination and the number of elements; the size of an element is
inferred automatically.
It checks if the multiplication of size and element count overflows.
The inferred size is passed first to st_mult, which allows the division
there to be done at compilation time.
As a basic type safety check it makes sure the sizes of source and
destination elements are the same. That's evaluated at compilation time
as well.
COPY_ARRAY is safe to use with NULL as source pointer iff 0 elements are
to be copied. That convention is used in some cases for initializing
arrays. Raw memcpy(3) does not support it -- compilers are allowed to
assume that only valid pointers are passed to it and can optimize away
NULL checks after such a call.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
git-compat-util.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/git-compat-util.h b/git-compat-util.h
index 37cce07..91775ce 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -801,6 +801,14 @@ extern FILE *fopen_for_writing(const char *path);
#define ALLOC_ARRAY(x, alloc) (x) = xmalloc(st_mult(sizeof(*(x)), (alloc)))
#define REALLOC_ARRAY(x, alloc) (x) = xrealloc((x), st_mult(sizeof(*(x)), (alloc)))
+#define COPY_ARRAY(dst, src, n) copy_array((dst), (src), (n), sizeof(*(dst)) + \
+ BUILD_ASSERT_OR_ZERO(sizeof(*(dst)) == sizeof(*(src))))
+static inline void copy_array(void *dst, const void *src, size_t n, size_t size)
+{
+ if (n)
+ memcpy(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:
--
2.10.0
next reply other threads:[~2016-09-25 7:16 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-25 7:15 René Scharfe [this message]
2016-09-25 7:24 ` [PATCH 6/7] use COPY_ARRAY René Scharfe
2016-09-25 7:26 ` René Scharfe
2016-09-25 7:41 ` [PATCH 1/2] add COPY_ARRAY Jeff King
2016-09-25 8:58 ` René Scharfe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6f402d35-b483-7552-2fb2-a5350112b8a6@web.de \
--to=l.s.r@web.de \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=peff@peff.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).