From fba4168edecdd2781bcd83cb131977ec1157f87c Mon Sep 17 00:00:00 2001
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Mon, 6 Apr 2020 20:11:52 -0700
Subject: [PATCH] gcov: gcc_4_7: replace zero-length array with flexible-array
member
The current codebase makes use of the zero-length array language extension
to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by this
change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Link: http://lkml.kernel.org/r/20200213152241.GA877@embeddedor
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/gcov/gcc_4_7.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
index ec37563674d624..908fdf5098c32e 100644
--- a/kernel/gcov/gcc_4_7.c
+++ b/kernel/gcov/gcc_4_7.c
@@ -68,7 +68,7 @@ struct gcov_fn_info {
unsigned int ident;
unsigned int lineno_checksum;
unsigned int cfg_checksum;
- struct gcov_ctr_info ctrs[0];
+ struct gcov_ctr_info ctrs[];
};
/**
--
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