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mfd: pm8xxx: Replace zero-length array with flexible-array member

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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 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Gustavo A. R. Silva 2020-02-12 17:59:11 -06:00 committed by Lee Jones
parent a0c8498c07
commit 7235d9e48f
1 changed files with 1 additions and 1 deletions
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2
drivers/mfd/qcom-pm8xxx.c
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@ -76,7 +76,7 @@ struct pm_irq_chip {
unsigned int num_masters;
const struct pm_irq_data *pm_irq_data;
/* MUST BE AT THE END OF THIS STRUCT */
u8 config[0];
u8 config[];
};
static int pm8xxx_read_block_irq(struct pm_irq_chip *chip, unsigned int bp,