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pcmcia: Replace zero-length array with flexible-array 

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

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
5.9.x+fslc
Gustavo A. R. Silva 2020-05-07 14:05:49 -05:00 committed by Dominik Brodowski
parent b9bbe6ed63
commit 06ed6aa56f
1 changed files with 3 additions and 3 deletions
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6
include/pcmcia/cistpl.h
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@ -161,7 +161,7 @@ typedef struct cistpl_funcid_t {
typedef struct cistpl_funce_t {
u_char type;
u_char data[0];
u_char data[];
} cistpl_funce_t;
/*======================================================================
@ -255,7 +255,7 @@ typedef struct cistpl_data_serv_t {
u_char escape;
u_char encrypt;
u_char misc_features;
u_char ccitt_code[0];
u_char ccitt_code[];
} cistpl_data_serv_t;
typedef struct cistpl_fax_serv_t {
@ -265,7 +265,7 @@ typedef struct cistpl_fax_serv_t {
u_char encrypt;
u_char features_0;
u_char features_1;
u_char ccitt_code[0];
u_char ccitt_code[];
} cistpl_fax_serv_t;
typedef struct cistpl_voice_serv_t {