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GustavoARSilvamasahir0y
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modpost,fixdep: 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] KSPP#21 [3] commit 7649773 ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Lines changed: 3 additions & 3 deletions

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‎scripts/basic/fixdep.c‎

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@@ -160,7 +160,7 @@ struct item {
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struct item *next;
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unsigned int len;
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unsigned int hash;
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char name[0];
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char name[];
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};
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#define HASHSZ 256

‎scripts/mod/modpost.c‎

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@@ -166,7 +166,7 @@ struct symbol {
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* (only for external modules) **/
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unsigned int is_static:1; /* 1 if symbol is not global */
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enum export export; /* Type of export */
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char name[0];
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char name[];
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};
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static struct symbol *symbolhash[SYMBOL_HASH_SIZE];

‎scripts/mod/modpost.h‎

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@@ -111,7 +111,7 @@ buf_write(struct buffer *buf, const char *s, int len);
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struct namespace_list {
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struct namespace_list *next;
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char namespace[0];
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char namespace[];
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};
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struct module {

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