* [PATCH] compat: let git_mmap use malloc(3) directly
@ 2021-08-21 12:52 René Scharfe
2021-08-23 16:15 ` Jeff King
2021-08-23 20:27 ` Johannes Schindelin
0 siblings, 2 replies; 3+ messages in thread
From: René Scharfe @ 2021-08-21 12:52 UTC (permalink / raw)
To: Git List; +Cc: Junio C Hamano, Johannes Schindelin
xmalloc() dies on error, allows zero-sized allocations and enforces
GIT_ALLOC_LIMIT for testing. Our mmap replacement doesn't need any of
that. Let's cut out the wrapper, reject zero-sized requests as required
by POSIX and use malloc(3) directly. Allocation errors were needlessly
handled by git_mmap() before; this code becomes reachable now.
Signed-off-by: René Scharfe <l.s.r@web.de>
---
compat/mmap.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/compat/mmap.c b/compat/mmap.c
index 14d31010df..8d6c02d4bc 100644
--- a/compat/mmap.c
+++ b/compat/mmap.c
@@ -7,7 +7,12 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of
if (start != NULL || flags != MAP_PRIVATE || prot != PROT_READ)
die("Invalid usage of mmap when built with NO_MMAP");
- start = xmalloc(length);
+ if (length == 0) {
+ errno = EINVAL;
+ return MAP_FAILED;
+ }
+
+ start = malloc(length);
if (start == NULL) {
errno = ENOMEM;
return MAP_FAILED;
--
2.33.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] compat: let git_mmap use malloc(3) directly
2021-08-21 12:52 [PATCH] compat: let git_mmap use malloc(3) directly René Scharfe
@ 2021-08-23 16:15 ` Jeff King
2021-08-23 20:27 ` Johannes Schindelin
1 sibling, 0 replies; 3+ messages in thread
From: Jeff King @ 2021-08-23 16:15 UTC (permalink / raw)
To: René Scharfe; +Cc: Git List, Junio C Hamano, Johannes Schindelin
On Sat, Aug 21, 2021 at 02:52:40PM +0200, René Scharfe wrote:
> xmalloc() dies on error, allows zero-sized allocations and enforces
> GIT_ALLOC_LIMIT for testing. Our mmap replacement doesn't need any of
> that. Let's cut out the wrapper, reject zero-sized requests as required
> by POSIX and use malloc(3) directly. Allocation errors were needlessly
> handled by git_mmap() before; this code becomes reachable now.
Thanks, this is a good idea. As you note, the function was already
expecting a possible NULL return. And I think in general it's good for
our compat/ wrappers to stay as close to the OS-level functions they're
emulating as possible.
-Peff
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] compat: let git_mmap use malloc(3) directly
2021-08-21 12:52 [PATCH] compat: let git_mmap use malloc(3) directly René Scharfe
2021-08-23 16:15 ` Jeff King
@ 2021-08-23 20:27 ` Johannes Schindelin
1 sibling, 0 replies; 3+ messages in thread
From: Johannes Schindelin @ 2021-08-23 20:27 UTC (permalink / raw)
To: René Scharfe; +Cc: Git List, Junio C Hamano
[-- Attachment #1: Type: text/plain, Size: 1241 bytes --]
Hi René,
On Sat, 21 Aug 2021, René Scharfe wrote:
> xmalloc() dies on error, allows zero-sized allocations and enforces
> GIT_ALLOC_LIMIT for testing. Our mmap replacement doesn't need any of
> that. Let's cut out the wrapper, reject zero-sized requests as required
> by POSIX and use malloc(3) directly. Allocation errors were needlessly
> handled by git_mmap() before; this code becomes reachable now.
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Thanks!
Dscho
>
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
> compat/mmap.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/compat/mmap.c b/compat/mmap.c
> index 14d31010df..8d6c02d4bc 100644
> --- a/compat/mmap.c
> +++ b/compat/mmap.c
> @@ -7,7 +7,12 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of
> if (start != NULL || flags != MAP_PRIVATE || prot != PROT_READ)
> die("Invalid usage of mmap when built with NO_MMAP");
>
> - start = xmalloc(length);
> + if (length == 0) {
> + errno = EINVAL;
> + return MAP_FAILED;
> + }
> +
> + start = malloc(length);
> if (start == NULL) {
> errno = ENOMEM;
> return MAP_FAILED;
> --
> 2.33.0
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-08-21 12:52 [PATCH] compat: let git_mmap use malloc(3) directly René Scharfe
2021-08-23 16:15 ` Jeff King
2021-08-23 20:27 ` Johannes Schindelin
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