* [PATCH] treewide: Replace zero-length array with flexible-array
@ 2020-05-07 18:54 Gustavo A. R. Silva
2020-05-07 20:08 ` Winkler, Tomas
0 siblings, 1 reply; 8+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-07 18:54 UTC (permalink / raw)
To: Tomas Winkler; +Cc: linux-kernel
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]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
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 <gustavoars@kernel.org>
---
samples/mei/mei-amt-version.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/samples/mei/mei-amt-version.c b/samples/mei/mei-amt-version.c
index 32234481ad7d..ad3e56042f96 100644
--- a/samples/mei/mei-amt-version.c
+++ b/samples/mei/mei-amt-version.c
@@ -267,7 +267,7 @@ struct amt_host_if_msg_header {
struct amt_host_if_resp_header {
struct amt_host_if_msg_header header;
uint32_t status;
- unsigned char data[0];
+ unsigned char data[];
} __attribute__((packed));
const uuid_le MEI_IAMTHIF = UUID_LE(0x12f80028, 0xb4b7, 0x4b2d, \
^ permalink raw reply related [flat|nested] 8+ messages in thread
* RE: [PATCH] treewide: Replace zero-length array with flexible-array
2020-05-07 18:54 [PATCH] treewide: Replace zero-length array with flexible-array Gustavo A. R. Silva
@ 2020-05-07 20:08 ` Winkler, Tomas
0 siblings, 0 replies; 8+ messages in thread
From: Winkler, Tomas @ 2020-05-07 20:08 UTC (permalink / raw)
To: Gustavo A. R. Silva; +Cc: linux-kernel
> -----Original Message-----
> From: Gustavo A. R. Silva <gustavoars@kernel.org>
> Sent: Thursday, May 07, 2020 21:54
> To: Winkler, Tomas <tomas.winkler@intel.com>
> Cc: linux-kernel@vger.kernel.org
> Subject: [PATCH] treewide: Replace zero-length array with flexible-array
Ack.
>
> 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]
>
> sizeof(flexible-array-member) triggers a warning because flexible array
> members have incomplete type[1]. There are some instances of code in which
> the sizeof operator is being incorrectly/erroneously applied to zero-length
> arrays and the result is zero. Such instances may be hiding some bugs. So, this
> work (flexible-array member conversions) will also help to get completely rid of
> those sorts of issues.
>
> 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 <gustavoars@kernel.org>
> ---
> samples/mei/mei-amt-version.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/samples/mei/mei-amt-version.c b/samples/mei/mei-amt-version.c
> index 32234481ad7d..ad3e56042f96 100644
> --- a/samples/mei/mei-amt-version.c
> +++ b/samples/mei/mei-amt-version.c
> @@ -267,7 +267,7 @@ struct amt_host_if_msg_header { struct
> amt_host_if_resp_header {
> struct amt_host_if_msg_header header;
> uint32_t status;
> - unsigned char data[0];
> + unsigned char data[];
> } __attribute__((packed));
>
> const uuid_le MEI_IAMTHIF = UUID_LE(0x12f80028, 0xb4b7, 0x4b2d, \
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] treewide: Replace zero-length array with flexible-array
2020-05-07 18:53 Gustavo A. R. Silva
@ 2020-05-22 21:24 ` Li Yang
0 siblings, 0 replies; 8+ messages in thread
From: Li Yang @ 2020-05-22 21:24 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: linuxppc-dev,
moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE, lkml
On Thu, May 7, 2020 at 1:49 PM Gustavo A. R. Silva
<gustavoars@kernel.org> wrote:
>
> 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]
>
> sizeof(flexible-array-member) triggers a warning because flexible array
> members have incomplete type[1]. There are some instances of code in
> which the sizeof operator is being incorrectly/erroneously applied to
> zero-length arrays and the result is zero. Such instances may be hiding
> some bugs. So, this work (flexible-array member conversions) will also
> help to get completely rid of those sorts of issues.
>
> 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 <gustavoars@kernel.org>
> ---
> include/linux/fsl/bestcomm/bestcomm.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Applied for next. Thanks.
Regards,
Leo
>
> diff --git a/include/linux/fsl/bestcomm/bestcomm.h b/include/linux/fsl/bestcomm/bestcomm.h
> index a0e2e6b19b57..154e541ce57e 100644
> --- a/include/linux/fsl/bestcomm/bestcomm.h
> +++ b/include/linux/fsl/bestcomm/bestcomm.h
> @@ -27,7 +27,7 @@
> */
> struct bcom_bd {
> u32 status;
> - u32 data[0]; /* variable payload size */
> + u32 data[]; /* variable payload size */
> };
>
> /* ======================================================================== */
>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] treewide: Replace zero-length array with flexible-array
2020-05-07 18:53 Gustavo A. R. Silva
@ 2020-05-13 14:59 ` Johan Hovold
0 siblings, 0 replies; 8+ messages in thread
From: Johan Hovold @ 2020-05-13 14:59 UTC (permalink / raw)
To: Gustavo A. R. Silva; +Cc: Johan Hovold, linux-kernel
On Thu, May 07, 2020 at 01:53:13PM -0500, Gustavo A. R. Silva wrote:
> 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]
>
> sizeof(flexible-array-member) triggers a warning because flexible array
> members have incomplete type[1]. There are some instances of code in
> which the sizeof operator is being incorrectly/erroneously applied to
> zero-length arrays and the result is zero. Such instances may be hiding
> some bugs. So, this work (flexible-array member conversions) will also
> help to get completely rid of those sorts of issues.
>
> 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 <gustavoars@kernel.org>
Applied for -next, thanks.
Johan
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] treewide: Replace zero-length array with flexible-array
2020-05-07 18:53 Gustavo A. R. Silva
@ 2020-05-07 19:43 ` Luck, Tony
0 siblings, 0 replies; 8+ messages in thread
From: Luck, Tony @ 2020-05-07 19:43 UTC (permalink / raw)
To: Gustavo A. R. Silva; +Cc: Fenghua Yu, linux-ia64, linux-kernel
On Thu, May 07, 2020 at 01:53:34PM -0500, Gustavo A. R. Silva wrote:
> 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]
>
> sizeof(flexible-array-member) triggers a warning because flexible array
> members have incomplete type[1]. There are some instances of code in
> which the sizeof operator is being incorrectly/erroneously applied to
> zero-length arrays and the result is zero. Such instances may be hiding
> some bugs. So, this work (flexible-array member conversions) will also
> help to get completely rid of those sorts of issues.
>
> 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 <gustavoars@kernel.org>
I'm fine with this specific change ... so
Acked-by: Tony Luck <tony.luck@intel.com>
for anyone picking up all of these treewide: patches
(if they don't, then I can apply this to the ia64 tree)
But a question ... is sizeof still ok on a structure that
contains a flexible-array-member?
E.g. I'd expect:
struct foo {
int stuff;
struct boo array[];
};
printk("size of foo = %d\n", sizeof(struct foo));
To not give any complilation warnings and to tell me that
the size of the structure is 4 bytes.
Is that still true and OK?
-Tony
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] treewide: Replace zero-length array with flexible-array
@ 2020-05-07 18:53 Gustavo A. R. Silva
2020-05-07 19:43 ` Luck, Tony
0 siblings, 1 reply; 8+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-07 18:53 UTC (permalink / raw)
To: Tony Luck, Fenghua Yu; +Cc: linux-ia64, linux-kernel
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]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
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 <gustavoars@kernel.org>
---
arch/ia64/kernel/unwind_i.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/unwind_i.h b/arch/ia64/kernel/unwind_i.h
index 67994a7e5816..1dd57ba44327 100644
--- a/arch/ia64/kernel/unwind_i.h
+++ b/arch/ia64/kernel/unwind_i.h
@@ -42,7 +42,7 @@ enum unw_register_index {
struct unw_info_block {
u64 header;
- u64 desc[0]; /* unwind descriptors */
+ u64 desc[]; /* unwind descriptors */
/* personality routine and language-specific data follow behind descriptors */
};
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH] treewide: Replace zero-length array with flexible-array
@ 2020-05-07 18:53 Gustavo A. R. Silva
2020-05-13 14:59 ` Johan Hovold
0 siblings, 1 reply; 8+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-07 18:53 UTC (permalink / raw)
To: Johan Hovold; +Cc: linux-kernel
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]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
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 <gustavoars@kernel.org>
---
drivers/gnss/serial.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gnss/serial.h b/drivers/gnss/serial.h
index 980ffdc86c2a..621953f7821d 100644
--- a/drivers/gnss/serial.h
+++ b/drivers/gnss/serial.h
@@ -16,7 +16,7 @@ struct gnss_serial {
struct gnss_device *gdev;
speed_t speed;
const struct gnss_serial_ops *ops;
- unsigned long drvdata[0];
+ unsigned long drvdata[];
};
enum gnss_serial_pm_state {
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH] treewide: Replace zero-length array with flexible-array
@ 2020-05-07 18:53 Gustavo A. R. Silva
2020-05-22 21:24 ` Li Yang
0 siblings, 1 reply; 8+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-07 18:53 UTC (permalink / raw)
To: Li Yang; +Cc: linuxppc-dev, linux-arm-kernel, linux-kernel
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]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
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 <gustavoars@kernel.org>
---
include/linux/fsl/bestcomm/bestcomm.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/fsl/bestcomm/bestcomm.h b/include/linux/fsl/bestcomm/bestcomm.h
index a0e2e6b19b57..154e541ce57e 100644
--- a/include/linux/fsl/bestcomm/bestcomm.h
+++ b/include/linux/fsl/bestcomm/bestcomm.h
@@ -27,7 +27,7 @@
*/
struct bcom_bd {
u32 status;
- u32 data[0]; /* variable payload size */
+ u32 data[]; /* variable payload size */
};
/* ======================================================================== */
^ permalink raw reply related [flat|nested] 8+ messages in thread
end of thread, other threads:[~2020-05-22 21:25 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
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2020-05-07 18:54 [PATCH] treewide: Replace zero-length array with flexible-array Gustavo A. R. Silva
2020-05-07 20:08 ` Winkler, Tomas
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2020-05-07 18:53 Gustavo A. R. Silva
2020-05-07 19:43 ` Luck, Tony
2020-05-07 18:53 Gustavo A. R. Silva
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2020-05-07 18:53 Gustavo A. R. Silva
2020-05-22 21:24 ` Li Yang
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