remoteproc: 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 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Gustavo A. R. Silva committed 6 years ago

Commit 529798b1 parent 8a226e21 file · +3 −3Browse files

Showing the changes to include/linux (1 of 1 file). Show all

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include/linux/remoteproc.h+3−3

@@ -73,7 +73,7 @@ struct resource_table { · 72 unmodified lines
73	73	u32 ver;
74	74	u32 num;
75	75	u32 reserved[2];
76		− u32 offset[0];
	76	+ u32 offset[];
77	77	} __packed;
78	78
79	79	/**
@@ -87,7 +87,7 @@ struct resource_table { · 7 unmodified lines
87	87	*/
88	88	struct fw_rsc_hdr {
89	89	u32 type;
90		− u8 data[0];
	90	+ u8 data[];
91	91	} __packed;
92	92
93	93	/**
@@ -306,7 +306,7 @@ struct fw_rsc_vdev { · 212 unmodified lines
306	306	u8 status;
307	307	u8 num_of_vrings;
308	308	u8 reserved[2];
309		− struct fw_rsc_vdev_vring vring[0];
	309	+ struct fw_rsc_vdev_vring vring[];
310	310	} __packed;
311	311
312	312	struct rproc;