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@xxxxxxxxxx>
---
drivers/pci/pci.c | 2 +-
include/linux/pci.h | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 595fcf59843f..bb78f580814e 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1578,7 +1578,7 @@ EXPORT_SYMBOL(pci_restore_state);
struct pci_saved_state {
u32 config_space[16];
- struct pci_cap_saved_data cap[0];
+ struct pci_cap_saved_data cap[];
};
/**
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 83ce1cdf5676..0453ee458ab1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -279,7 +279,7 @@ struct pci_cap_saved_data {
u16 cap_nr;
bool cap_extended;
unsigned int size;
- u32 data[0];
+ u32 data[];
};
struct pci_cap_saved_state {
@@ -532,7 +532,7 @@ struct pci_host_bridge {
resource_size_t start,
resource_size_t size,
resource_size_t align);
- unsigned long private[0] ____cacheline_aligned;
+ unsigned long private[] ____cacheline_aligned;
};
#define to_pci_host_bridge(n) container_of(n, struct pci_host_bridge, dev)
